Pull d-states into release branch

[linux-2.6] / drivers / firewire / fw-ohci.c

/*
 * Driver for OHCI 1394 controllers
 *
 * Copyright (C) 2003-2006 Kristian Hoegsberg <krh@bitplanet.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <linux/dma-mapping.h>
#include <linux/mm.h>

#include <asm/uaccess.h>
#include <asm/semaphore.h>

#include "fw-transaction.h"
#include "fw-ohci.h"

#define DESCRIPTOR_OUTPUT_MORE          0
#define DESCRIPTOR_OUTPUT_LAST          (1 << 12)
#define DESCRIPTOR_INPUT_MORE           (2 << 12)
#define DESCRIPTOR_INPUT_LAST           (3 << 12)
#define DESCRIPTOR_STATUS               (1 << 11)
#define DESCRIPTOR_KEY_IMMEDIATE        (2 << 8)
#define DESCRIPTOR_PING                 (1 << 7)
#define DESCRIPTOR_YY                   (1 << 6)
#define DESCRIPTOR_NO_IRQ               (0 << 4)
#define DESCRIPTOR_IRQ_ERROR            (1 << 4)
#define DESCRIPTOR_IRQ_ALWAYS           (3 << 4)
#define DESCRIPTOR_BRANCH_ALWAYS        (3 << 2)
#define DESCRIPTOR_WAIT                 (3 << 0)

struct descriptor {
        __le16 req_count;
        __le16 control;
        __le32 data_address;
        __le32 branch_address;
        __le16 res_count;
        __le16 transfer_status;
} __attribute__((aligned(16)));

struct db_descriptor {
        __le16 first_size;
        __le16 control;
        __le16 second_req_count;
        __le16 first_req_count;
        __le32 branch_address;
        __le16 second_res_count;
        __le16 first_res_count;
        __le32 reserved0;
        __le32 first_buffer;
        __le32 second_buffer;
        __le32 reserved1;
} __attribute__((aligned(16)));

#define CONTROL_SET(regs)       (regs)
#define CONTROL_CLEAR(regs)     ((regs) + 4)
#define COMMAND_PTR(regs)       ((regs) + 12)
#define CONTEXT_MATCH(regs)     ((regs) + 16)

struct ar_buffer {
        struct descriptor descriptor;
        struct ar_buffer *next;
        __le32 data[0];
};

struct ar_context {
        struct fw_ohci *ohci;
        struct ar_buffer *current_buffer;
        struct ar_buffer *last_buffer;
        void *pointer;
        u32 regs;
        struct tasklet_struct tasklet;
};

struct context;

typedef int (*descriptor_callback_t)(struct context *ctx,
                                     struct descriptor *d,
                                     struct descriptor *last);
struct context {
        struct fw_ohci *ohci;
        u32 regs;

        struct descriptor *buffer;
        dma_addr_t buffer_bus;
        size_t buffer_size;
        struct descriptor *head_descriptor;
        struct descriptor *tail_descriptor;
        struct descriptor *tail_descriptor_last;
        struct descriptor *prev_descriptor;

        descriptor_callback_t callback;

        struct tasklet_struct tasklet;
};

#define IT_HEADER_SY(v)          ((v) <<  0)
#define IT_HEADER_TCODE(v)       ((v) <<  4)
#define IT_HEADER_CHANNEL(v)     ((v) <<  8)
#define IT_HEADER_TAG(v)         ((v) << 14)
#define IT_HEADER_SPEED(v)       ((v) << 16)
#define IT_HEADER_DATA_LENGTH(v) ((v) << 16)

struct iso_context {
        struct fw_iso_context base;
        struct context context;
        void *header;
        size_t header_length;
};

#define CONFIG_ROM_SIZE 1024

struct fw_ohci {
        struct fw_card card;

        u32 version;
        __iomem char *registers;
        dma_addr_t self_id_bus;
        __le32 *self_id_cpu;
        struct tasklet_struct bus_reset_tasklet;
        int node_id;
        int generation;
        int request_generation;
        u32 bus_seconds;

        /*
         * Spinlock for accessing fw_ohci data.  Never call out of
         * this driver with this lock held.
         */
        spinlock_t lock;
        u32 self_id_buffer[512];

        /* Config rom buffers */
        __be32 *config_rom;
        dma_addr_t config_rom_bus;
        __be32 *next_config_rom;
        dma_addr_t next_config_rom_bus;
        u32 next_header;

        struct ar_context ar_request_ctx;
        struct ar_context ar_response_ctx;
        struct context at_request_ctx;
        struct context at_response_ctx;

        u32 it_context_mask;
        struct iso_context *it_context_list;
        u32 ir_context_mask;
        struct iso_context *ir_context_list;
};

static inline struct fw_ohci *fw_ohci(struct fw_card *card)
{
        return container_of(card, struct fw_ohci, card);
}

#define IT_CONTEXT_CYCLE_MATCH_ENABLE   0x80000000
#define IR_CONTEXT_BUFFER_FILL          0x80000000
#define IR_CONTEXT_ISOCH_HEADER         0x40000000
#define IR_CONTEXT_CYCLE_MATCH_ENABLE   0x20000000
#define IR_CONTEXT_MULTI_CHANNEL_MODE   0x10000000
#define IR_CONTEXT_DUAL_BUFFER_MODE     0x08000000

#define CONTEXT_RUN     0x8000
#define CONTEXT_WAKE    0x1000
#define CONTEXT_DEAD    0x0800
#define CONTEXT_ACTIVE  0x0400

#define OHCI1394_MAX_AT_REQ_RETRIES     0x2
#define OHCI1394_MAX_AT_RESP_RETRIES    0x2
#define OHCI1394_MAX_PHYS_RESP_RETRIES  0x8

#define FW_OHCI_MAJOR                   240
#define OHCI1394_REGISTER_SIZE          0x800
#define OHCI_LOOP_COUNT                 500
#define OHCI1394_PCI_HCI_Control        0x40
#define SELF_ID_BUF_SIZE                0x800
#define OHCI_TCODE_PHY_PACKET           0x0e
#define OHCI_VERSION_1_1                0x010010
#define ISO_BUFFER_SIZE                 (64 * 1024)
#define AT_BUFFER_SIZE                  4096

static char ohci_driver_name[] = KBUILD_MODNAME;

static inline void reg_write(const struct fw_ohci *ohci, int offset, u32 data)
{
        writel(data, ohci->registers + offset);
}

static inline u32 reg_read(const struct fw_ohci *ohci, int offset)
{
        return readl(ohci->registers + offset);
}

static inline void flush_writes(const struct fw_ohci *ohci)
{
        /* Do a dummy read to flush writes. */
        reg_read(ohci, OHCI1394_Version);
}

static int
ohci_update_phy_reg(struct fw_card *card, int addr,
                    int clear_bits, int set_bits)
{
        struct fw_ohci *ohci = fw_ohci(card);
        u32 val, old;

        reg_write(ohci, OHCI1394_PhyControl, OHCI1394_PhyControl_Read(addr));
        flush_writes(ohci);
        msleep(2);
        val = reg_read(ohci, OHCI1394_PhyControl);
        if ((val & OHCI1394_PhyControl_ReadDone) == 0) {
                fw_error("failed to set phy reg bits.\n");
                return -EBUSY;
        }

        old = OHCI1394_PhyControl_ReadData(val);
        old = (old & ~clear_bits) | set_bits;
        reg_write(ohci, OHCI1394_PhyControl,
                  OHCI1394_PhyControl_Write(addr, old));

        return 0;
}

static int ar_context_add_page(struct ar_context *ctx)
{
        struct device *dev = ctx->ohci->card.device;
        struct ar_buffer *ab;
        dma_addr_t ab_bus;
        size_t offset;

        ab = (struct ar_buffer *) __get_free_page(GFP_ATOMIC);
        if (ab == NULL)
                return -ENOMEM;

        ab_bus = dma_map_single(dev, ab, PAGE_SIZE, DMA_BIDIRECTIONAL);
        if (dma_mapping_error(ab_bus)) {
                free_page((unsigned long) ab);
                return -ENOMEM;
        }

        memset(&ab->descriptor, 0, sizeof(ab->descriptor));
        ab->descriptor.control        = cpu_to_le16(DESCRIPTOR_INPUT_MORE |
                                                    DESCRIPTOR_STATUS |
                                                    DESCRIPTOR_BRANCH_ALWAYS);
        offset = offsetof(struct ar_buffer, data);
        ab->descriptor.req_count      = cpu_to_le16(PAGE_SIZE - offset);
        ab->descriptor.data_address   = cpu_to_le32(ab_bus + offset);
        ab->descriptor.res_count      = cpu_to_le16(PAGE_SIZE - offset);
        ab->descriptor.branch_address = 0;

        dma_sync_single_for_device(dev, ab_bus, PAGE_SIZE, DMA_BIDIRECTIONAL);

        ctx->last_buffer->descriptor.branch_address = cpu_to_le32(ab_bus | 1);
        ctx->last_buffer->next = ab;
        ctx->last_buffer = ab;

        reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
        flush_writes(ctx->ohci);

        return 0;
}

static __le32 *handle_ar_packet(struct ar_context *ctx, __le32 *buffer)
{
        struct fw_ohci *ohci = ctx->ohci;
        struct fw_packet p;
        u32 status, length, tcode;

        p.header[0] = le32_to_cpu(buffer[0]);
        p.header[1] = le32_to_cpu(buffer[1]);
        p.header[2] = le32_to_cpu(buffer[2]);

        tcode = (p.header[0] >> 4) & 0x0f;
        switch (tcode) {
        case TCODE_WRITE_QUADLET_REQUEST:
        case TCODE_READ_QUADLET_RESPONSE:
                p.header[3] = (__force __u32) buffer[3];
                p.header_length = 16;
                p.payload_length = 0;
                break;

        case TCODE_READ_BLOCK_REQUEST :
                p.header[3] = le32_to_cpu(buffer[3]);
                p.header_length = 16;
                p.payload_length = 0;
                break;

        case TCODE_WRITE_BLOCK_REQUEST:
        case TCODE_READ_BLOCK_RESPONSE:
        case TCODE_LOCK_REQUEST:
        case TCODE_LOCK_RESPONSE:
                p.header[3] = le32_to_cpu(buffer[3]);
                p.header_length = 16;
                p.payload_length = p.header[3] >> 16;
                break;

        case TCODE_WRITE_RESPONSE:
        case TCODE_READ_QUADLET_REQUEST:
        case OHCI_TCODE_PHY_PACKET:
                p.header_length = 12;
                p.payload_length = 0;
                break;
        }

        p.payload = (void *) buffer + p.header_length;

        /* FIXME: What to do about evt_* errors? */
        length = (p.header_length + p.payload_length + 3) / 4;
        status = le32_to_cpu(buffer[length]);

        p.ack        = ((status >> 16) & 0x1f) - 16;
        p.speed      = (status >> 21) & 0x7;
        p.timestamp  = status & 0xffff;
        p.generation = ohci->request_generation;

        /*
         * The OHCI bus reset handler synthesizes a phy packet with
         * the new generation number when a bus reset happens (see
         * section 8.4.2.3).  This helps us determine when a request
         * was received and make sure we send the response in the same
         * generation.  We only need this for requests; for responses
         * we use the unique tlabel for finding the matching
         * request.
         */

        if (p.ack + 16 == 0x09)
                ohci->request_generation = (buffer[2] >> 16) & 0xff;
        else if (ctx == &ohci->ar_request_ctx)
                fw_core_handle_request(&ohci->card, &p);
        else
                fw_core_handle_response(&ohci->card, &p);

        return buffer + length + 1;
}

static void ar_context_tasklet(unsigned long data)
{
        struct ar_context *ctx = (struct ar_context *)data;
        struct fw_ohci *ohci = ctx->ohci;
        struct ar_buffer *ab;
        struct descriptor *d;
        void *buffer, *end;

        ab = ctx->current_buffer;
        d = &ab->descriptor;

        if (d->res_count == 0) {
                size_t size, rest, offset;

                /*
                 * This descriptor is finished and we may have a
                 * packet split across this and the next buffer. We
                 * reuse the page for reassembling the split packet.
                 */

                offset = offsetof(struct ar_buffer, data);
                dma_unmap_single(ohci->card.device,
                        le32_to_cpu(ab->descriptor.data_address) - offset,
                        PAGE_SIZE, DMA_BIDIRECTIONAL);

                buffer = ab;
                ab = ab->next;
                d = &ab->descriptor;
                size = buffer + PAGE_SIZE - ctx->pointer;
                rest = le16_to_cpu(d->req_count) - le16_to_cpu(d->res_count);
                memmove(buffer, ctx->pointer, size);
                memcpy(buffer + size, ab->data, rest);
                ctx->current_buffer = ab;
                ctx->pointer = (void *) ab->data + rest;
                end = buffer + size + rest;

                while (buffer < end)
                        buffer = handle_ar_packet(ctx, buffer);

                free_page((unsigned long)buffer);
                ar_context_add_page(ctx);
        } else {
                buffer = ctx->pointer;
                ctx->pointer = end =
                        (void *) ab + PAGE_SIZE - le16_to_cpu(d->res_count);

                while (buffer < end)
                        buffer = handle_ar_packet(ctx, buffer);
        }
}

static int
ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci, u32 regs)
{
        struct ar_buffer ab;

        ctx->regs        = regs;
        ctx->ohci        = ohci;
        ctx->last_buffer = &ab;
        tasklet_init(&ctx->tasklet, ar_context_tasklet, (unsigned long)ctx);

        ar_context_add_page(ctx);
        ar_context_add_page(ctx);
        ctx->current_buffer = ab.next;
        ctx->pointer = ctx->current_buffer->data;

        return 0;
}

static void ar_context_run(struct ar_context *ctx)
{
        struct ar_buffer *ab = ctx->current_buffer;
        dma_addr_t ab_bus;
        size_t offset;

        offset = offsetof(struct ar_buffer, data);
        ab_bus = le32_to_cpu(ab->descriptor.data_address) - offset;

        reg_write(ctx->ohci, COMMAND_PTR(ctx->regs), ab_bus | 1);
        reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_RUN);
        flush_writes(ctx->ohci);
}

static void context_tasklet(unsigned long data)
{
        struct context *ctx = (struct context *) data;
        struct fw_ohci *ohci = ctx->ohci;
        struct descriptor *d, *last;
        u32 address;
        int z;

        dma_sync_single_for_cpu(ohci->card.device, ctx->buffer_bus,
                                ctx->buffer_size, DMA_TO_DEVICE);

        d    = ctx->tail_descriptor;
        last = ctx->tail_descriptor_last;

        while (last->branch_address != 0) {
                address = le32_to_cpu(last->branch_address);
                z = address & 0xf;
                d = ctx->buffer + (address - ctx->buffer_bus) / sizeof(*d);
                last = (z == 2) ? d : d + z - 1;

                if (!ctx->callback(ctx, d, last))
                        break;

                ctx->tail_descriptor      = d;
                ctx->tail_descriptor_last = last;
        }
}

static int
context_init(struct context *ctx, struct fw_ohci *ohci,
             size_t buffer_size, u32 regs,
             descriptor_callback_t callback)
{
        ctx->ohci = ohci;
        ctx->regs = regs;
        ctx->buffer_size = buffer_size;
        ctx->buffer = kmalloc(buffer_size, GFP_KERNEL);
        if (ctx->buffer == NULL)
                return -ENOMEM;

        tasklet_init(&ctx->tasklet, context_tasklet, (unsigned long)ctx);
        ctx->callback = callback;

        ctx->buffer_bus =
                dma_map_single(ohci->card.device, ctx->buffer,
                               buffer_size, DMA_TO_DEVICE);
        if (dma_mapping_error(ctx->buffer_bus)) {
                kfree(ctx->buffer);
                return -ENOMEM;
        }

        ctx->head_descriptor      = ctx->buffer;
        ctx->prev_descriptor      = ctx->buffer;
        ctx->tail_descriptor      = ctx->buffer;
        ctx->tail_descriptor_last = ctx->buffer;

        /*
         * We put a dummy descriptor in the buffer that has a NULL
         * branch address and looks like it's been sent.  That way we
         * have a descriptor to append DMA programs to.  Also, the
         * ring buffer invariant is that it always has at least one
         * element so that head == tail means buffer full.
         */

        memset(ctx->head_descriptor, 0, sizeof(*ctx->head_descriptor));
        ctx->head_descriptor->control = cpu_to_le16(DESCRIPTOR_OUTPUT_LAST);
        ctx->head_descriptor->transfer_status = cpu_to_le16(0x8011);
        ctx->head_descriptor++;

        return 0;
}

static void
context_release(struct context *ctx)
{
        struct fw_card *card = &ctx->ohci->card;

        dma_unmap_single(card->device, ctx->buffer_bus,
                         ctx->buffer_size, DMA_TO_DEVICE);
        kfree(ctx->buffer);
}

static struct descriptor *
context_get_descriptors(struct context *ctx, int z, dma_addr_t *d_bus)
{
        struct descriptor *d, *tail, *end;

        d = ctx->head_descriptor;
        tail = ctx->tail_descriptor;
        end = ctx->buffer + ctx->buffer_size / sizeof(*d);

        if (d + z <= tail) {
                goto has_space;
        } else if (d > tail && d + z <= end) {
                goto has_space;
        } else if (d > tail && ctx->buffer + z <= tail) {
                d = ctx->buffer;
                goto has_space;
        }

        return NULL;

 has_space:
        memset(d, 0, z * sizeof(*d));
        *d_bus = ctx->buffer_bus + (d - ctx->buffer) * sizeof(*d);

        return d;
}

static void context_run(struct context *ctx, u32 extra)
{
        struct fw_ohci *ohci = ctx->ohci;

        reg_write(ohci, COMMAND_PTR(ctx->regs),
                  le32_to_cpu(ctx->tail_descriptor_last->branch_address));
        reg_write(ohci, CONTROL_CLEAR(ctx->regs), ~0);
        reg_write(ohci, CONTROL_SET(ctx->regs), CONTEXT_RUN | extra);
        flush_writes(ohci);
}

static void context_append(struct context *ctx,
                           struct descriptor *d, int z, int extra)
{
        dma_addr_t d_bus;

        d_bus = ctx->buffer_bus + (d - ctx->buffer) * sizeof(*d);

        ctx->head_descriptor = d + z + extra;
        ctx->prev_descriptor->branch_address = cpu_to_le32(d_bus | z);
        ctx->prev_descriptor = z == 2 ? d : d + z - 1;

        dma_sync_single_for_device(ctx->ohci->card.device, ctx->buffer_bus,
                                   ctx->buffer_size, DMA_TO_DEVICE);

        reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
        flush_writes(ctx->ohci);
}

static void context_stop(struct context *ctx)
{
        u32 reg;
        int i;

        reg_write(ctx->ohci, CONTROL_CLEAR(ctx->regs), CONTEXT_RUN);
        flush_writes(ctx->ohci);

        for (i = 0; i < 10; i++) {
                reg = reg_read(ctx->ohci, CONTROL_SET(ctx->regs));
                if ((reg & CONTEXT_ACTIVE) == 0)
                        break;

                fw_notify("context_stop: still active (0x%08x)\n", reg);
                mdelay(1);
        }
}

struct driver_data {
        struct fw_packet *packet;
};

/*
 * This function apppends a packet to the DMA queue for transmission.
 * Must always be called with the ochi->lock held to ensure proper
 * generation handling and locking around packet queue manipulation.
 */
static int
at_context_queue_packet(struct context *ctx, struct fw_packet *packet)
{
        struct fw_ohci *ohci = ctx->ohci;
        dma_addr_t d_bus, payload_bus;
        struct driver_data *driver_data;
        struct descriptor *d, *last;
        __le32 *header;
        int z, tcode;
        u32 reg;

        d = context_get_descriptors(ctx, 4, &d_bus);
        if (d == NULL) {
                packet->ack = RCODE_SEND_ERROR;
                return -1;
        }

        d[0].control   = cpu_to_le16(DESCRIPTOR_KEY_IMMEDIATE);
        d[0].res_count = cpu_to_le16(packet->timestamp);

        /*
         * The DMA format for asyncronous link packets is different
         * from the IEEE1394 layout, so shift the fields around
         * accordingly.  If header_length is 8, it's a PHY packet, to
         * which we need to prepend an extra quadlet.
         */

        header = (__le32 *) &d[1];
        if (packet->header_length > 8) {
                header[0] = cpu_to_le32((packet->header[0] & 0xffff) |
                                        (packet->speed << 16));
                header[1] = cpu_to_le32((packet->header[1] & 0xffff) |
                                        (packet->header[0] & 0xffff0000));
                header[2] = cpu_to_le32(packet->header[2]);

                tcode = (packet->header[0] >> 4) & 0x0f;
                if (TCODE_IS_BLOCK_PACKET(tcode))
                        header[3] = cpu_to_le32(packet->header[3]);
                else
                        header[3] = (__force __le32) packet->header[3];

                d[0].req_count = cpu_to_le16(packet->header_length);
        } else {
                header[0] = cpu_to_le32((OHCI1394_phy_tcode << 4) |
                                        (packet->speed << 16));
                header[1] = cpu_to_le32(packet->header[0]);
                header[2] = cpu_to_le32(packet->header[1]);
                d[0].req_count = cpu_to_le16(12);
        }

        driver_data = (struct driver_data *) &d[3];
        driver_data->packet = packet;
        packet->driver_data = driver_data;
        
        if (packet->payload_length > 0) {
                payload_bus =
                        dma_map_single(ohci->card.device, packet->payload,
                                       packet->payload_length, DMA_TO_DEVICE);
                if (dma_mapping_error(payload_bus)) {
                        packet->ack = RCODE_SEND_ERROR;
                        return -1;
                }

                d[2].req_count    = cpu_to_le16(packet->payload_length);
                d[2].data_address = cpu_to_le32(payload_bus);
                last = &d[2];
                z = 3;
        } else {
                last = &d[0];
                z = 2;
        }

        last->control |= cpu_to_le16(DESCRIPTOR_OUTPUT_LAST |
                                     DESCRIPTOR_IRQ_ALWAYS |
                                     DESCRIPTOR_BRANCH_ALWAYS);

        /* FIXME: Document how the locking works. */
        if (ohci->generation != packet->generation) {
                packet->ack = RCODE_GENERATION;
                return -1;
        }

        context_append(ctx, d, z, 4 - z);

        /* If the context isn't already running, start it up. */
        reg = reg_read(ctx->ohci, CONTROL_SET(ctx->regs));
        if ((reg & CONTEXT_RUN) == 0)
                context_run(ctx, 0);

        return 0;
}

static int handle_at_packet(struct context *context,
                            struct descriptor *d,
                            struct descriptor *last)
{
        struct driver_data *driver_data;
        struct fw_packet *packet;
        struct fw_ohci *ohci = context->ohci;
        dma_addr_t payload_bus;
        int evt;

        if (last->transfer_status == 0)
                /* This descriptor isn't done yet, stop iteration. */
                return 0;

        driver_data = (struct driver_data *) &d[3];
        packet = driver_data->packet;
        if (packet == NULL)
                /* This packet was cancelled, just continue. */
                return 1;

        payload_bus = le32_to_cpu(last->data_address);
        if (payload_bus != 0)
                dma_unmap_single(ohci->card.device, payload_bus,
                                 packet->payload_length, DMA_TO_DEVICE);

        evt = le16_to_cpu(last->transfer_status) & 0x1f;
        packet->timestamp = le16_to_cpu(last->res_count);

        switch (evt) {
        case OHCI1394_evt_timeout:
                /* Async response transmit timed out. */
                packet->ack = RCODE_CANCELLED;
                break;

        case OHCI1394_evt_flushed:
                /*
                 * The packet was flushed should give same error as
                 * when we try to use a stale generation count.
                 */
                packet->ack = RCODE_GENERATION;
                break;

        case OHCI1394_evt_missing_ack:
                /*
                 * Using a valid (current) generation count, but the
                 * node is not on the bus or not sending acks.
                 */
                packet->ack = RCODE_NO_ACK;
                break;

        case ACK_COMPLETE + 0x10:
        case ACK_PENDING + 0x10:
        case ACK_BUSY_X + 0x10:
        case ACK_BUSY_A + 0x10:
        case ACK_BUSY_B + 0x10:
        case ACK_DATA_ERROR + 0x10:
        case ACK_TYPE_ERROR + 0x10:
                packet->ack = evt - 0x10;
                break;

        default:
                packet->ack = RCODE_SEND_ERROR;
                break;
        }

        packet->callback(packet, &ohci->card, packet->ack);

        return 1;
}

#define HEADER_GET_DESTINATION(q)       (((q) >> 16) & 0xffff)
#define HEADER_GET_TCODE(q)             (((q) >> 4) & 0x0f)
#define HEADER_GET_OFFSET_HIGH(q)       (((q) >> 0) & 0xffff)
#define HEADER_GET_DATA_LENGTH(q)       (((q) >> 16) & 0xffff)
#define HEADER_GET_EXTENDED_TCODE(q)    (((q) >> 0) & 0xffff)

static void
handle_local_rom(struct fw_ohci *ohci, struct fw_packet *packet, u32 csr)
{
        struct fw_packet response;
        int tcode, length, i;

        tcode = HEADER_GET_TCODE(packet->header[0]);
        if (TCODE_IS_BLOCK_PACKET(tcode))
                length = HEADER_GET_DATA_LENGTH(packet->header[3]);
        else
                length = 4;

        i = csr - CSR_CONFIG_ROM;
        if (i + length > CONFIG_ROM_SIZE) {
                fw_fill_response(&response, packet->header,
                                 RCODE_ADDRESS_ERROR, NULL, 0);
        } else if (!TCODE_IS_READ_REQUEST(tcode)) {
                fw_fill_response(&response, packet->header,
                                 RCODE_TYPE_ERROR, NULL, 0);
        } else {
                fw_fill_response(&response, packet->header, RCODE_COMPLETE,
                                 (void *) ohci->config_rom + i, length);
        }

        fw_core_handle_response(&ohci->card, &response);
}

static void
handle_local_lock(struct fw_ohci *ohci, struct fw_packet *packet, u32 csr)
{
        struct fw_packet response;
        int tcode, length, ext_tcode, sel;
        __be32 *payload, lock_old;
        u32 lock_arg, lock_data;

        tcode = HEADER_GET_TCODE(packet->header[0]);
        length = HEADER_GET_DATA_LENGTH(packet->header[3]);
        payload = packet->payload;
        ext_tcode = HEADER_GET_EXTENDED_TCODE(packet->header[3]);

        if (tcode == TCODE_LOCK_REQUEST &&
            ext_tcode == EXTCODE_COMPARE_SWAP && length == 8) {
                lock_arg = be32_to_cpu(payload[0]);
                lock_data = be32_to_cpu(payload[1]);
        } else if (tcode == TCODE_READ_QUADLET_REQUEST) {
                lock_arg = 0;
                lock_data = 0;
        } else {
                fw_fill_response(&response, packet->header,
                                 RCODE_TYPE_ERROR, NULL, 0);
                goto out;
        }

        sel = (csr - CSR_BUS_MANAGER_ID) / 4;
        reg_write(ohci, OHCI1394_CSRData, lock_data);
        reg_write(ohci, OHCI1394_CSRCompareData, lock_arg);
        reg_write(ohci, OHCI1394_CSRControl, sel);

        if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000)
                lock_old = cpu_to_be32(reg_read(ohci, OHCI1394_CSRData));
        else
                fw_notify("swap not done yet\n");

        fw_fill_response(&response, packet->header,
                         RCODE_COMPLETE, &lock_old, sizeof(lock_old));
 out:
        fw_core_handle_response(&ohci->card, &response);
}

static void
handle_local_request(struct context *ctx, struct fw_packet *packet)
{
        u64 offset;
        u32 csr;

        if (ctx == &ctx->ohci->at_request_ctx) {
                packet->ack = ACK_PENDING;
                packet->callback(packet, &ctx->ohci->card, packet->ack);
        }

        offset =
                ((unsigned long long)
                 HEADER_GET_OFFSET_HIGH(packet->header[1]) << 32) |
                packet->header[2];
        csr = offset - CSR_REGISTER_BASE;

        /* Handle config rom reads. */
        if (csr >= CSR_CONFIG_ROM && csr < CSR_CONFIG_ROM_END)
                handle_local_rom(ctx->ohci, packet, csr);
        else switch (csr) {
        case CSR_BUS_MANAGER_ID:
        case CSR_BANDWIDTH_AVAILABLE:
        case CSR_CHANNELS_AVAILABLE_HI:
        case CSR_CHANNELS_AVAILABLE_LO:
                handle_local_lock(ctx->ohci, packet, csr);
                break;
        default:
                if (ctx == &ctx->ohci->at_request_ctx)
                        fw_core_handle_request(&ctx->ohci->card, packet);
                else
                        fw_core_handle_response(&ctx->ohci->card, packet);
                break;
        }

        if (ctx == &ctx->ohci->at_response_ctx) {
                packet->ack = ACK_COMPLETE;
                packet->callback(packet, &ctx->ohci->card, packet->ack);
        }
}

static void
at_context_transmit(struct context *ctx, struct fw_packet *packet)
{
        unsigned long flags;
        int retval;

        spin_lock_irqsave(&ctx->ohci->lock, flags);

        if (HEADER_GET_DESTINATION(packet->header[0]) == ctx->ohci->node_id &&
            ctx->ohci->generation == packet->generation) {
                spin_unlock_irqrestore(&ctx->ohci->lock, flags);
                handle_local_request(ctx, packet);
                return;
        }

        retval = at_context_queue_packet(ctx, packet);
        spin_unlock_irqrestore(&ctx->ohci->lock, flags);

        if (retval < 0)
                packet->callback(packet, &ctx->ohci->card, packet->ack);
        
}

static void bus_reset_tasklet(unsigned long data)
{
        struct fw_ohci *ohci = (struct fw_ohci *)data;
        int self_id_count, i, j, reg;
        int generation, new_generation;
        unsigned long flags;

        reg = reg_read(ohci, OHCI1394_NodeID);
        if (!(reg & OHCI1394_NodeID_idValid)) {
                fw_error("node ID not valid, new bus reset in progress\n");
                return;
        }
        ohci->node_id = reg & 0xffff;

        /*
         * The count in the SelfIDCount register is the number of
         * bytes in the self ID receive buffer.  Since we also receive
         * the inverted quadlets and a header quadlet, we shift one
         * bit extra to get the actual number of self IDs.
         */

        self_id_count = (reg_read(ohci, OHCI1394_SelfIDCount) >> 3) & 0x3ff;
        generation = (le32_to_cpu(ohci->self_id_cpu[0]) >> 16) & 0xff;

        for (i = 1, j = 0; j < self_id_count; i += 2, j++) {
                if (ohci->self_id_cpu[i] != ~ohci->self_id_cpu[i + 1])
                        fw_error("inconsistent self IDs\n");
                ohci->self_id_buffer[j] = le32_to_cpu(ohci->self_id_cpu[i]);
        }

        /*
         * Check the consistency of the self IDs we just read.  The
         * problem we face is that a new bus reset can start while we
         * read out the self IDs from the DMA buffer. If this happens,
         * the DMA buffer will be overwritten with new self IDs and we
         * will read out inconsistent data.  The OHCI specification
         * (section 11.2) recommends a technique similar to
         * linux/seqlock.h, where we remember the generation of the
         * self IDs in the buffer before reading them out and compare
         * it to the current generation after reading them out.  If
         * the two generations match we know we have a consistent set
         * of self IDs.
         */

        new_generation = (reg_read(ohci, OHCI1394_SelfIDCount) >> 16) & 0xff;
        if (new_generation != generation) {
                fw_notify("recursive bus reset detected, "
                          "discarding self ids\n");
                return;
        }

        /* FIXME: Document how the locking works. */
        spin_lock_irqsave(&ohci->lock, flags);

        ohci->generation = generation;
        context_stop(&ohci->at_request_ctx);
        context_stop(&ohci->at_response_ctx);
        reg_write(ohci, OHCI1394_IntEventClear, OHCI1394_busReset);

        /*
         * This next bit is unrelated to the AT context stuff but we
         * have to do it under the spinlock also.  If a new config rom
         * was set up before this reset, the old one is now no longer
         * in use and we can free it. Update the config rom pointers
         * to point to the current config rom and clear the
         * next_config_rom pointer so a new udpate can take place.
         */

        if (ohci->next_config_rom != NULL) {
                dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                  ohci->config_rom, ohci->config_rom_bus);
                ohci->config_rom      = ohci->next_config_rom;
                ohci->config_rom_bus  = ohci->next_config_rom_bus;
                ohci->next_config_rom = NULL;

                /*
                 * Restore config_rom image and manually update
                 * config_rom registers.  Writing the header quadlet
                 * will indicate that the config rom is ready, so we
                 * do that last.
                 */
                reg_write(ohci, OHCI1394_BusOptions,
                          be32_to_cpu(ohci->config_rom[2]));
                ohci->config_rom[0] = cpu_to_be32(ohci->next_header);
                reg_write(ohci, OHCI1394_ConfigROMhdr, ohci->next_header);
        }

        spin_unlock_irqrestore(&ohci->lock, flags);

        fw_core_handle_bus_reset(&ohci->card, ohci->node_id, generation,
                                 self_id_count, ohci->self_id_buffer);
}

static irqreturn_t irq_handler(int irq, void *data)
{
        struct fw_ohci *ohci = data;
        u32 event, iso_event, cycle_time;
        int i;

        event = reg_read(ohci, OHCI1394_IntEventClear);

        if (!event || !~event)
                return IRQ_NONE;

        reg_write(ohci, OHCI1394_IntEventClear, event);

        if (event & OHCI1394_selfIDComplete)
                tasklet_schedule(&ohci->bus_reset_tasklet);

        if (event & OHCI1394_RQPkt)
                tasklet_schedule(&ohci->ar_request_ctx.tasklet);

        if (event & OHCI1394_RSPkt)
                tasklet_schedule(&ohci->ar_response_ctx.tasklet);

        if (event & OHCI1394_reqTxComplete)
                tasklet_schedule(&ohci->at_request_ctx.tasklet);

        if (event & OHCI1394_respTxComplete)
                tasklet_schedule(&ohci->at_response_ctx.tasklet);

        iso_event = reg_read(ohci, OHCI1394_IsoRecvIntEventClear);
        reg_write(ohci, OHCI1394_IsoRecvIntEventClear, iso_event);

        while (iso_event) {
                i = ffs(iso_event) - 1;
                tasklet_schedule(&ohci->ir_context_list[i].context.tasklet);
                iso_event &= ~(1 << i);
        }

        iso_event = reg_read(ohci, OHCI1394_IsoXmitIntEventClear);
        reg_write(ohci, OHCI1394_IsoXmitIntEventClear, iso_event);

        while (iso_event) {
                i = ffs(iso_event) - 1;
                tasklet_schedule(&ohci->it_context_list[i].context.tasklet);
                iso_event &= ~(1 << i);
        }

        if (event & OHCI1394_cycle64Seconds) {
                cycle_time = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
                if ((cycle_time & 0x80000000) == 0)
                        ohci->bus_seconds++;
        }

        return IRQ_HANDLED;
}

static int software_reset(struct fw_ohci *ohci)
{
        int i;

        reg_write(ohci, OHCI1394_HCControlSet, OHCI1394_HCControl_softReset);

        for (i = 0; i < OHCI_LOOP_COUNT; i++) {
                if ((reg_read(ohci, OHCI1394_HCControlSet) &
                     OHCI1394_HCControl_softReset) == 0)
                        return 0;
                msleep(1);
        }

        return -EBUSY;
}

static int ohci_enable(struct fw_card *card, u32 *config_rom, size_t length)
{
        struct fw_ohci *ohci = fw_ohci(card);
        struct pci_dev *dev = to_pci_dev(card->device);

        if (software_reset(ohci)) {
                fw_error("Failed to reset ohci card.\n");
                return -EBUSY;
        }

        /*
         * Now enable LPS, which we need in order to start accessing
         * most of the registers.  In fact, on some cards (ALI M5251),
         * accessing registers in the SClk domain without LPS enabled
         * will lock up the machine.  Wait 50msec to make sure we have
         * full link enabled.
         */
        reg_write(ohci, OHCI1394_HCControlSet,
                  OHCI1394_HCControl_LPS |
                  OHCI1394_HCControl_postedWriteEnable);
        flush_writes(ohci);
        msleep(50);

        reg_write(ohci, OHCI1394_HCControlClear,
                  OHCI1394_HCControl_noByteSwapData);

        reg_write(ohci, OHCI1394_LinkControlSet,
                  OHCI1394_LinkControl_rcvSelfID |
                  OHCI1394_LinkControl_cycleTimerEnable |
                  OHCI1394_LinkControl_cycleMaster);

        reg_write(ohci, OHCI1394_ATRetries,
                  OHCI1394_MAX_AT_REQ_RETRIES |
                  (OHCI1394_MAX_AT_RESP_RETRIES << 4) |
                  (OHCI1394_MAX_PHYS_RESP_RETRIES << 8));

        ar_context_run(&ohci->ar_request_ctx);
        ar_context_run(&ohci->ar_response_ctx);

        reg_write(ohci, OHCI1394_SelfIDBuffer, ohci->self_id_bus);
        reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000);
        reg_write(ohci, OHCI1394_IntEventClear, ~0);
        reg_write(ohci, OHCI1394_IntMaskClear, ~0);
        reg_write(ohci, OHCI1394_IntMaskSet,
                  OHCI1394_selfIDComplete |
                  OHCI1394_RQPkt | OHCI1394_RSPkt |
                  OHCI1394_reqTxComplete | OHCI1394_respTxComplete |
                  OHCI1394_isochRx | OHCI1394_isochTx |
                  OHCI1394_masterIntEnable |
                  OHCI1394_cycle64Seconds);

        /* Activate link_on bit and contender bit in our self ID packets.*/
        if (ohci_update_phy_reg(card, 4, 0,
                                PHY_LINK_ACTIVE | PHY_CONTENDER) < 0)
                return -EIO;

        /*
         * When the link is not yet enabled, the atomic config rom
         * update mechanism described below in ohci_set_config_rom()
         * is not active.  We have to update ConfigRomHeader and
         * BusOptions manually, and the write to ConfigROMmap takes
         * effect immediately.  We tie this to the enabling of the
         * link, so we have a valid config rom before enabling - the
         * OHCI requires that ConfigROMhdr and BusOptions have valid
         * values before enabling.
         *
         * However, when the ConfigROMmap is written, some controllers
         * always read back quadlets 0 and 2 from the config rom to
         * the ConfigRomHeader and BusOptions registers on bus reset.
         * They shouldn't do that in this initial case where the link
         * isn't enabled.  This means we have to use the same
         * workaround here, setting the bus header to 0 and then write
         * the right values in the bus reset tasklet.
         */

        ohci->next_config_rom =
                dma_alloc_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                   &ohci->next_config_rom_bus, GFP_KERNEL);
        if (ohci->next_config_rom == NULL)
                return -ENOMEM;

        memset(ohci->next_config_rom, 0, CONFIG_ROM_SIZE);
        fw_memcpy_to_be32(ohci->next_config_rom, config_rom, length * 4);

        ohci->next_header = config_rom[0];
        ohci->next_config_rom[0] = 0;
        reg_write(ohci, OHCI1394_ConfigROMhdr, 0);
        reg_write(ohci, OHCI1394_BusOptions, config_rom[2]);
        reg_write(ohci, OHCI1394_ConfigROMmap, ohci->next_config_rom_bus);

        reg_write(ohci, OHCI1394_AsReqFilterHiSet, 0x80000000);

        if (request_irq(dev->irq, irq_handler,
                        IRQF_SHARED, ohci_driver_name, ohci)) {
                fw_error("Failed to allocate shared interrupt %d.\n",
                         dev->irq);
                dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                  ohci->config_rom, ohci->config_rom_bus);
                return -EIO;
        }

        reg_write(ohci, OHCI1394_HCControlSet,
                  OHCI1394_HCControl_linkEnable |
                  OHCI1394_HCControl_BIBimageValid);
        flush_writes(ohci);

        /*
         * We are ready to go, initiate bus reset to finish the
         * initialization.
         */

        fw_core_initiate_bus_reset(&ohci->card, 1);

        return 0;
}

static int
ohci_set_config_rom(struct fw_card *card, u32 *config_rom, size_t length)
{
        struct fw_ohci *ohci;
        unsigned long flags;
        int retval = 0;
        __be32 *next_config_rom;
        dma_addr_t next_config_rom_bus;

        ohci = fw_ohci(card);

        /*
         * When the OHCI controller is enabled, the config rom update
         * mechanism is a bit tricky, but easy enough to use.  See
         * section 5.5.6 in the OHCI specification.
         *
         * The OHCI controller caches the new config rom address in a
         * shadow register (ConfigROMmapNext) and needs a bus reset
         * for the changes to take place.  When the bus reset is
         * detected, the controller loads the new values for the
         * ConfigRomHeader and BusOptions registers from the specified
         * config rom and loads ConfigROMmap from the ConfigROMmapNext
         * shadow register. All automatically and atomically.
         *
         * Now, there's a twist to this story.  The automatic load of
         * ConfigRomHeader and BusOptions doesn't honor the
         * noByteSwapData bit, so with a be32 config rom, the
         * controller will load be32 values in to these registers
         * during the atomic update, even on litte endian
         * architectures.  The workaround we use is to put a 0 in the
         * header quadlet; 0 is endian agnostic and means that the
         * config rom isn't ready yet.  In the bus reset tasklet we
         * then set up the real values for the two registers.
         *
         * We use ohci->lock to avoid racing with the code that sets
         * ohci->next_config_rom to NULL (see bus_reset_tasklet).
         */

        next_config_rom =
                dma_alloc_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                   &next_config_rom_bus, GFP_KERNEL);
        if (next_config_rom == NULL)
                return -ENOMEM;

        spin_lock_irqsave(&ohci->lock, flags);

        if (ohci->next_config_rom == NULL) {
                ohci->next_config_rom = next_config_rom;
                ohci->next_config_rom_bus = next_config_rom_bus;

                memset(ohci->next_config_rom, 0, CONFIG_ROM_SIZE);
                fw_memcpy_to_be32(ohci->next_config_rom, config_rom,
                                  length * 4);

                ohci->next_header = config_rom[0];
                ohci->next_config_rom[0] = 0;

                reg_write(ohci, OHCI1394_ConfigROMmap,
                          ohci->next_config_rom_bus);
        } else {
                dma_free_coherent(ohci->card.device, CONFIG_ROM_SIZE,
                                  next_config_rom, next_config_rom_bus);
                retval = -EBUSY;
        }

        spin_unlock_irqrestore(&ohci->lock, flags);

        /*
         * Now initiate a bus reset to have the changes take
         * effect. We clean up the old config rom memory and DMA
         * mappings in the bus reset tasklet, since the OHCI
         * controller could need to access it before the bus reset
         * takes effect.
         */
        if (retval == 0)
                fw_core_initiate_bus_reset(&ohci->card, 1);

        return retval;
}

static void ohci_send_request(struct fw_card *card, struct fw_packet *packet)
{
        struct fw_ohci *ohci = fw_ohci(card);

        at_context_transmit(&ohci->at_request_ctx, packet);
}

static void ohci_send_response(struct fw_card *card, struct fw_packet *packet)
{
        struct fw_ohci *ohci = fw_ohci(card);

        at_context_transmit(&ohci->at_response_ctx, packet);
}

static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
{
        struct fw_ohci *ohci = fw_ohci(card);
        struct context *ctx = &ohci->at_request_ctx;
        struct driver_data *driver_data = packet->driver_data;
        int retval = -ENOENT;

        tasklet_disable(&ctx->tasklet);

        if (packet->ack != 0)
                goto out;

        driver_data->packet = NULL;
        packet->ack = RCODE_CANCELLED;
        packet->callback(packet, &ohci->card, packet->ack);
        retval = 0;

 out:
        tasklet_enable(&ctx->tasklet);

        return retval;
}

static int
ohci_enable_phys_dma(struct fw_card *card, int node_id, int generation)
{
        struct fw_ohci *ohci = fw_ohci(card);
        unsigned long flags;
        int n, retval = 0;

        /*
         * FIXME:  Make sure this bitmask is cleared when we clear the busReset
         * interrupt bit.  Clear physReqResourceAllBuses on bus reset.
         */

        spin_lock_irqsave(&ohci->lock, flags);

        if (ohci->generation != generation) {
                retval = -ESTALE;
                goto out;
        }

        /*
         * Note, if the node ID contains a non-local bus ID, physical DMA is
         * enabled for _all_ nodes on remote buses.
         */

        n = (node_id & 0xffc0) == LOCAL_BUS ? node_id & 0x3f : 63;
        if (n < 32)
                reg_write(ohci, OHCI1394_PhyReqFilterLoSet, 1 << n);
        else
                reg_write(ohci, OHCI1394_PhyReqFilterHiSet, 1 << (n - 32));

        flush_writes(ohci);
 out:
        spin_unlock_irqrestore(&ohci->lock, flags);
        return retval;
}

static u64
ohci_get_bus_time(struct fw_card *card)
{
        struct fw_ohci *ohci = fw_ohci(card);
        u32 cycle_time;
        u64 bus_time;

        cycle_time = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
        bus_time = ((u64) ohci->bus_seconds << 32) | cycle_time;

        return bus_time;
}

static int handle_ir_dualbuffer_packet(struct context *context,
                                       struct descriptor *d,
                                       struct descriptor *last)
{
        struct iso_context *ctx =
                container_of(context, struct iso_context, context);
        struct db_descriptor *db = (struct db_descriptor *) d;
        __le32 *ir_header;
        size_t header_length;
        void *p, *end;
        int i;

        if (db->first_res_count > 0 && db->second_res_count > 0)
                /* This descriptor isn't done yet, stop iteration. */
                return 0;

        header_length = le16_to_cpu(db->first_req_count) -
                le16_to_cpu(db->first_res_count);

        i = ctx->header_length;
        p = db + 1;
        end = p + header_length;
        while (p < end && i + ctx->base.header_size <= PAGE_SIZE) {
                /*
                 * The iso header is byteswapped to little endian by
                 * the controller, but the remaining header quadlets
                 * are big endian.  We want to present all the headers
                 * as big endian, so we have to swap the first
                 * quadlet.
                 */
                *(u32 *) (ctx->header + i) = __swab32(*(u32 *) (p + 4));
                memcpy(ctx->header + i + 4, p + 8, ctx->base.header_size - 4);
                i += ctx->base.header_size;
                p += ctx->base.header_size + 4;
        }

        ctx->header_length = i;

        if (le16_to_cpu(db->control) & DESCRIPTOR_IRQ_ALWAYS) {
                ir_header = (__le32 *) (db + 1);
                ctx->base.callback(&ctx->base,
                                   le32_to_cpu(ir_header[0]) & 0xffff,
                                   ctx->header_length, ctx->header,
                                   ctx->base.callback_data);
                ctx->header_length = 0;
        }

        return 1;
}

static int handle_it_packet(struct context *context,
                            struct descriptor *d,
                            struct descriptor *last)
{
        struct iso_context *ctx =
                container_of(context, struct iso_context, context);

        if (last->transfer_status == 0)
                /* This descriptor isn't done yet, stop iteration. */
                return 0;

        if (le16_to_cpu(last->control) & DESCRIPTOR_IRQ_ALWAYS)
                ctx->base.callback(&ctx->base, le16_to_cpu(last->res_count),
                                   0, NULL, ctx->base.callback_data);

        return 1;
}

static struct fw_iso_context *
ohci_allocate_iso_context(struct fw_card *card, int type, size_t header_size)
{
        struct fw_ohci *ohci = fw_ohci(card);
        struct iso_context *ctx, *list;
        descriptor_callback_t callback;
        u32 *mask, regs;
        unsigned long flags;
        int index, retval = -ENOMEM;

        if (type == FW_ISO_CONTEXT_TRANSMIT) {
                mask = &ohci->it_context_mask;
                list = ohci->it_context_list;
                callback = handle_it_packet;
        } else {
                mask = &ohci->ir_context_mask;
                list = ohci->ir_context_list;
                callback = handle_ir_dualbuffer_packet;
        }

        /* FIXME: We need a fallback for pre 1.1 OHCI. */
        if (callback == handle_ir_dualbuffer_packet &&
            ohci->version < OHCI_VERSION_1_1)
                return ERR_PTR(-EINVAL);

        spin_lock_irqsave(&ohci->lock, flags);
        index = ffs(*mask) - 1;
        if (index >= 0)
                *mask &= ~(1 << index);
        spin_unlock_irqrestore(&ohci->lock, flags);

        if (index < 0)
                return ERR_PTR(-EBUSY);

        if (type == FW_ISO_CONTEXT_TRANSMIT)
                regs = OHCI1394_IsoXmitContextBase(index);
        else
                regs = OHCI1394_IsoRcvContextBase(index);

        ctx = &list[index];
        memset(ctx, 0, sizeof(*ctx));
        ctx->header_length = 0;
        ctx->header = (void *) __get_free_page(GFP_KERNEL);
        if (ctx->header == NULL)
                goto out;

        retval = context_init(&ctx->context, ohci, ISO_BUFFER_SIZE,
                              regs, callback);
        if (retval < 0)
                goto out_with_header;

        return &ctx->base;

 out_with_header:
        free_page((unsigned long)ctx->header);
 out:
        spin_lock_irqsave(&ohci->lock, flags);
        *mask |= 1 << index;
        spin_unlock_irqrestore(&ohci->lock, flags);

        return ERR_PTR(retval);
}

static int ohci_start_iso(struct fw_iso_context *base,
                          s32 cycle, u32 sync, u32 tags)
{
        struct iso_context *ctx = container_of(base, struct iso_context, base);
        struct fw_ohci *ohci = ctx->context.ohci;
        u32 control, match;
        int index;

        if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
                index = ctx - ohci->it_context_list;
                match = 0;
                if (cycle >= 0)
                        match = IT_CONTEXT_CYCLE_MATCH_ENABLE |
                                (cycle & 0x7fff) << 16;

                reg_write(ohci, OHCI1394_IsoXmitIntEventClear, 1 << index);
                reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, 1 << index);
                context_run(&ctx->context, match);
        } else {
                index = ctx - ohci->ir_context_list;
                control = IR_CONTEXT_DUAL_BUFFER_MODE | IR_CONTEXT_ISOCH_HEADER;
                match = (tags << 28) | (sync << 8) | ctx->base.channel;
                if (cycle >= 0) {
                        match |= (cycle & 0x07fff) << 12;
                        control |= IR_CONTEXT_CYCLE_MATCH_ENABLE;
                }

                reg_write(ohci, OHCI1394_IsoRecvIntEventClear, 1 << index);
                reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, 1 << index);
                reg_write(ohci, CONTEXT_MATCH(ctx->context.regs), match);
                context_run(&ctx->context, control);
        }

        return 0;
}

static int ohci_stop_iso(struct fw_iso_context *base)
{
        struct fw_ohci *ohci = fw_ohci(base->card);
        struct iso_context *ctx = container_of(base, struct iso_context, base);
        int index;

        if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
                index = ctx - ohci->it_context_list;
                reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, 1 << index);
        } else {
                index = ctx - ohci->ir_context_list;
                reg_write(ohci, OHCI1394_IsoRecvIntMaskClear, 1 << index);
        }
        flush_writes(ohci);
        context_stop(&ctx->context);

        return 0;
}

static void ohci_free_iso_context(struct fw_iso_context *base)
{
        struct fw_ohci *ohci = fw_ohci(base->card);
        struct iso_context *ctx = container_of(base, struct iso_context, base);
        unsigned long flags;
        int index;

        ohci_stop_iso(base);
        context_release(&ctx->context);
        free_page((unsigned long)ctx->header);

        spin_lock_irqsave(&ohci->lock, flags);

        if (ctx->base.type == FW_ISO_CONTEXT_TRANSMIT) {
                index = ctx - ohci->it_context_list;
                ohci->it_context_mask |= 1 << index;
        } else {
                index = ctx - ohci->ir_context_list;
                ohci->ir_context_mask |= 1 << index;
        }

        spin_unlock_irqrestore(&ohci->lock, flags);
}

static int
ohci_queue_iso_transmit(struct fw_iso_context *base,
                        struct fw_iso_packet *packet,
                        struct fw_iso_buffer *buffer,
                        unsigned long payload)
{
        struct iso_context *ctx = container_of(base, struct iso_context, base);
        struct descriptor *d, *last, *pd;
        struct fw_iso_packet *p;
        __le32 *header;
        dma_addr_t d_bus, page_bus;
        u32 z, header_z, payload_z, irq;
        u32 payload_index, payload_end_index, next_page_index;
        int page, end_page, i, length, offset;

        /*
         * FIXME: Cycle lost behavior should be configurable: lose
         * packet, retransmit or terminate..
         */

        p = packet;
        payload_index = payload;

        if (p->skip)
                z = 1;
        else
                z = 2;
        if (p->header_length > 0)
                z++;

        /* Determine the first page the payload isn't contained in. */
        end_page = PAGE_ALIGN(payload_index + p->payload_length) >> PAGE_SHIFT;
        if (p->payload_length > 0)
                payload_z = end_page - (payload_index >> PAGE_SHIFT);
        else
                payload_z = 0;

        z += payload_z;

        /* Get header size in number of descriptors. */
        header_z = DIV_ROUND_UP(p->header_length, sizeof(*d));

        d = context_get_descriptors(&ctx->context, z + header_z, &d_bus);
        if (d == NULL)
                return -ENOMEM;

        if (!p->skip) {
                d[0].control   = cpu_to_le16(DESCRIPTOR_KEY_IMMEDIATE);
                d[0].req_count = cpu_to_le16(8);

                header = (__le32 *) &d[1];
                header[0] = cpu_to_le32(IT_HEADER_SY(p->sy) |
                                        IT_HEADER_TAG(p->tag) |
                                        IT_HEADER_TCODE(TCODE_STREAM_DATA) |
                                        IT_HEADER_CHANNEL(ctx->base.channel) |
                                        IT_HEADER_SPEED(ctx->base.speed));
                header[1] =
                        cpu_to_le32(IT_HEADER_DATA_LENGTH(p->header_length +
                                                          p->payload_length));
        }

        if (p->header_length > 0) {
                d[2].req_count    = cpu_to_le16(p->header_length);
                d[2].data_address = cpu_to_le32(d_bus + z * sizeof(*d));
                memcpy(&d[z], p->header, p->header_length);
        }

        pd = d + z - payload_z;
        payload_end_index = payload_index + p->payload_length;
        for (i = 0; i < payload_z; i++) {
                page               = payload_index >> PAGE_SHIFT;
                offset             = payload_index & ~PAGE_MASK;
                next_page_index    = (page + 1) << PAGE_SHIFT;
                length             =
                        min(next_page_index, payload_end_index) - payload_index;
                pd[i].req_count    = cpu_to_le16(length);

                page_bus = page_private(buffer->pages[page]);
                pd[i].data_address = cpu_to_le32(page_bus + offset);

                payload_index += length;
        }

        if (p->interrupt)
                irq = DESCRIPTOR_IRQ_ALWAYS;
        else
                irq = DESCRIPTOR_NO_IRQ;

        last = z == 2 ? d : d + z - 1;
        last->control |= cpu_to_le16(DESCRIPTOR_OUTPUT_LAST |
                                     DESCRIPTOR_STATUS |
                                     DESCRIPTOR_BRANCH_ALWAYS |
                                     irq);

        context_append(&ctx->context, d, z, header_z);

        return 0;
}

static int
ohci_queue_iso_receive_dualbuffer(struct fw_iso_context *base,
                                  struct fw_iso_packet *packet,
                                  struct fw_iso_buffer *buffer,
                                  unsigned long payload)
{
        struct iso_context *ctx = container_of(base, struct iso_context, base);
        struct db_descriptor *db = NULL;
        struct descriptor *d;
        struct fw_iso_packet *p;
        dma_addr_t d_bus, page_bus;
        u32 z, header_z, length, rest;
        int page, offset, packet_count, header_size;

        /*
         * FIXME: Cycle lost behavior should be configurable: lose
         * packet, retransmit or terminate..
         */

        if (packet->skip) {
                d = context_get_descriptors(&ctx->context, 2, &d_bus);
                if (d == NULL)
                        return -ENOMEM;

                db = (struct db_descriptor *) d;
                db->control = cpu_to_le16(DESCRIPTOR_STATUS |
                                          DESCRIPTOR_BRANCH_ALWAYS |
                                          DESCRIPTOR_WAIT);
                db->first_size = cpu_to_le16(ctx->base.header_size + 4);
                context_append(&ctx->context, d, 2, 0);
        }

        p = packet;
        z = 2;

        /*
         * The OHCI controller puts the status word in the header
         * buffer too, so we need 4 extra bytes per packet.
         */
        packet_count = p->header_length / ctx->base.header_size;
        header_size = packet_count * (ctx->base.header_size + 4);

        /* Get header size in number of descriptors. */
        header_z = DIV_ROUND_UP(header_size, sizeof(*d));
        page     = payload >> PAGE_SHIFT;
        offset   = payload & ~PAGE_MASK;
        rest     = p->payload_length;

        /* FIXME: OHCI 1.0 doesn't support dual buffer receive */
        /* FIXME: make packet-per-buffer/dual-buffer a context option */
        while (rest > 0) {
                d = context_get_descriptors(&ctx->context,
                                            z + header_z, &d_bus);
                if (d == NULL)
                        return -ENOMEM;

                db = (struct db_descriptor *) d;
                db->control = cpu_to_le16(DESCRIPTOR_STATUS |
                                          DESCRIPTOR_BRANCH_ALWAYS);
                db->first_size = cpu_to_le16(ctx->base.header_size + 4);
                db->first_req_count = cpu_to_le16(header_size);
                db->first_res_count = db->first_req_count;
                db->first_buffer = cpu_to_le32(d_bus + sizeof(*db));

                if (offset + rest < PAGE_SIZE)
                        length = rest;
                else
                        length = PAGE_SIZE - offset;

                db->second_req_count = cpu_to_le16(length);
                db->second_res_count = db->second_req_count;
                page_bus = page_private(buffer->pages[page]);
                db->second_buffer = cpu_to_le32(page_bus + offset);

                if (p->interrupt && length == rest)
                        db->control |= cpu_to_le16(DESCRIPTOR_IRQ_ALWAYS);

                context_append(&ctx->context, d, z, header_z);
                offset = (offset + length) & ~PAGE_MASK;
                rest -= length;
                page++;
        }

        return 0;
}

static int
ohci_queue_iso(struct fw_iso_context *base,
               struct fw_iso_packet *packet,
               struct fw_iso_buffer *buffer,
               unsigned long payload)
{
        struct iso_context *ctx = container_of(base, struct iso_context, base);

        if (base->type == FW_ISO_CONTEXT_TRANSMIT)
                return ohci_queue_iso_transmit(base, packet, buffer, payload);
        else if (ctx->context.ohci->version >= OHCI_VERSION_1_1)
                return ohci_queue_iso_receive_dualbuffer(base, packet,
                                                         buffer, payload);
        else
                /* FIXME: Implement fallback for OHCI 1.0 controllers. */
                return -EINVAL;
}

static const struct fw_card_driver ohci_driver = {
        .name                   = ohci_driver_name,
        .enable                 = ohci_enable,
        .update_phy_reg         = ohci_update_phy_reg,
        .set_config_rom         = ohci_set_config_rom,
        .send_request           = ohci_send_request,
        .send_response          = ohci_send_response,
        .cancel_packet          = ohci_cancel_packet,
        .enable_phys_dma        = ohci_enable_phys_dma,
        .get_bus_time           = ohci_get_bus_time,

        .allocate_iso_context   = ohci_allocate_iso_context,
        .free_iso_context       = ohci_free_iso_context,
        .queue_iso              = ohci_queue_iso,
        .start_iso              = ohci_start_iso,
        .stop_iso               = ohci_stop_iso,
};

static int __devinit
pci_probe(struct pci_dev *dev, const struct pci_device_id *ent)
{
        struct fw_ohci *ohci;
        u32 bus_options, max_receive, link_speed;
        u64 guid;
        int err;
        size_t size;

        ohci = kzalloc(sizeof(*ohci), GFP_KERNEL);
        if (ohci == NULL) {
                fw_error("Could not malloc fw_ohci data.\n");
                return -ENOMEM;
        }

        fw_card_initialize(&ohci->card, &ohci_driver, &dev->dev);

        err = pci_enable_device(dev);
        if (err) {
                fw_error("Failed to enable OHCI hardware.\n");
                goto fail_put_card;
        }

        pci_set_master(dev);
        pci_write_config_dword(dev, OHCI1394_PCI_HCI_Control, 0);
        pci_set_drvdata(dev, ohci);

        spin_lock_init(&ohci->lock);

        tasklet_init(&ohci->bus_reset_tasklet,
                     bus_reset_tasklet, (unsigned long)ohci);

        err = pci_request_region(dev, 0, ohci_driver_name);
        if (err) {
                fw_error("MMIO resource unavailable\n");
                goto fail_disable;
        }

        ohci->registers = pci_iomap(dev, 0, OHCI1394_REGISTER_SIZE);
        if (ohci->registers == NULL) {
                fw_error("Failed to remap registers\n");
                err = -ENXIO;
                goto fail_iomem;
        }

        ar_context_init(&ohci->ar_request_ctx, ohci,
                        OHCI1394_AsReqRcvContextControlSet);

        ar_context_init(&ohci->ar_response_ctx, ohci,
                        OHCI1394_AsRspRcvContextControlSet);

        context_init(&ohci->at_request_ctx, ohci, AT_BUFFER_SIZE,
                     OHCI1394_AsReqTrContextControlSet, handle_at_packet);

        context_init(&ohci->at_response_ctx, ohci, AT_BUFFER_SIZE,
                     OHCI1394_AsRspTrContextControlSet, handle_at_packet);

        reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, ~0);
        ohci->it_context_mask = reg_read(ohci, OHCI1394_IsoRecvIntMaskSet);
        reg_write(ohci, OHCI1394_IsoRecvIntMaskClear, ~0);
        size = sizeof(struct iso_context) * hweight32(ohci->it_context_mask);
        ohci->it_context_list = kzalloc(size, GFP_KERNEL);

        reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, ~0);
        ohci->ir_context_mask = reg_read(ohci, OHCI1394_IsoXmitIntMaskSet);
        reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, ~0);
        size = sizeof(struct iso_context) * hweight32(ohci->ir_context_mask);
        ohci->ir_context_list = kzalloc(size, GFP_KERNEL);

        if (ohci->it_context_list == NULL || ohci->ir_context_list == NULL) {
                fw_error("Out of memory for it/ir contexts.\n");
                err = -ENOMEM;
                goto fail_registers;
        }

        /* self-id dma buffer allocation */
        ohci->self_id_cpu = dma_alloc_coherent(ohci->card.device,
                                               SELF_ID_BUF_SIZE,
                                               &ohci->self_id_bus,
                                               GFP_KERNEL);
        if (ohci->self_id_cpu == NULL) {
                fw_error("Out of memory for self ID buffer.\n");
                err = -ENOMEM;
                goto fail_registers;
        }

        bus_options = reg_read(ohci, OHCI1394_BusOptions);
        max_receive = (bus_options >> 12) & 0xf;
        link_speed = bus_options & 0x7;
        guid = ((u64) reg_read(ohci, OHCI1394_GUIDHi) << 32) |
                reg_read(ohci, OHCI1394_GUIDLo);

        err = fw_card_add(&ohci->card, max_receive, link_speed, guid);
        if (err < 0)
                goto fail_self_id;

        ohci->version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
        fw_notify("Added fw-ohci device %s, OHCI version %x.%x\n",
                  dev->dev.bus_id, ohci->version >> 16, ohci->version & 0xff);

        return 0;

 fail_self_id:
        dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
                          ohci->self_id_cpu, ohci->self_id_bus);
 fail_registers:
        kfree(ohci->it_context_list);
        kfree(ohci->ir_context_list);
        pci_iounmap(dev, ohci->registers);
 fail_iomem:
        pci_release_region(dev, 0);
 fail_disable:
        pci_disable_device(dev);
 fail_put_card:
        fw_card_put(&ohci->card);

        return err;
}

static void pci_remove(struct pci_dev *dev)
{
        struct fw_ohci *ohci;

        ohci = pci_get_drvdata(dev);
        reg_write(ohci, OHCI1394_IntMaskClear, ~0);
        flush_writes(ohci);
        fw_core_remove_card(&ohci->card);

        /*
         * FIXME: Fail all pending packets here, now that the upper
         * layers can't queue any more.
         */

        software_reset(ohci);
        free_irq(dev->irq, ohci);
        dma_free_coherent(ohci->card.device, SELF_ID_BUF_SIZE,
                          ohci->self_id_cpu, ohci->self_id_bus);
        kfree(ohci->it_context_list);
        kfree(ohci->ir_context_list);
        pci_iounmap(dev, ohci->registers);
        pci_release_region(dev, 0);
        pci_disable_device(dev);
        fw_card_put(&ohci->card);

        fw_notify("Removed fw-ohci device.\n");
}

#ifdef CONFIG_PM
static int pci_suspend(struct pci_dev *pdev, pm_message_t state)
{
        struct fw_ohci *ohci = pci_get_drvdata(pdev);
        int err;

        software_reset(ohci);
        free_irq(pdev->irq, ohci);
        err = pci_save_state(pdev);
        if (err) {
                fw_error("pci_save_state failed\n");
                return err;
        }
        err = pci_set_power_state(pdev, pci_choose_state(pdev, state));
        if (err) {
                fw_error("pci_set_power_state failed\n");
                return err;
        }

        return 0;
}

static int pci_resume(struct pci_dev *pdev)
{
        struct fw_ohci *ohci = pci_get_drvdata(pdev);
        int err;

        pci_set_power_state(pdev, PCI_D0);
        pci_restore_state(pdev);
        err = pci_enable_device(pdev);
        if (err) {
                fw_error("pci_enable_device failed\n");
                return err;
        }

        return ohci_enable(&ohci->card, ohci->config_rom, CONFIG_ROM_SIZE);
}
#endif

static struct pci_device_id pci_table[] = {
        { PCI_DEVICE_CLASS(PCI_CLASS_SERIAL_FIREWIRE_OHCI, ~0) },
        { }
};

MODULE_DEVICE_TABLE(pci, pci_table);

static struct pci_driver fw_ohci_pci_driver = {
        .name           = ohci_driver_name,
        .id_table       = pci_table,
        .probe          = pci_probe,
        .remove         = pci_remove,
#ifdef CONFIG_PM
        .resume         = pci_resume,
        .suspend        = pci_suspend,
#endif
};

MODULE_AUTHOR("Kristian Hoegsberg <krh@bitplanet.net>");
MODULE_DESCRIPTION("Driver for PCI OHCI IEEE1394 controllers");
MODULE_LICENSE("GPL");

/* Provide a module alias so root-on-sbp2 initrds don't break. */
#ifndef CONFIG_IEEE1394_OHCI1394_MODULE
MODULE_ALIAS("ohci1394");
#endif

static int __init fw_ohci_init(void)
{
        return pci_register_driver(&fw_ohci_pci_driver);
}

static void __exit fw_ohci_cleanup(void)
{
        pci_unregister_driver(&fw_ohci_pci_driver);
}

module_init(fw_ohci_init);
module_exit(fw_ohci_cleanup);