Merge branch 'upstream-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/linvil...

[linux-2.6] / arch / powerpc / platforms / pseries / eeh.c

/*
 * eeh.c
 * Copyright (C) 2001 Dave Engebretsen & Todd Inglett IBM Corporation
 *
 * 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/delay.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/proc_fs.h>
#include <linux/rbtree.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <asm/atomic.h>
#include <asm/eeh.h>
#include <asm/eeh_event.h>
#include <asm/io.h>
#include <asm/machdep.h>
#include <asm/ppc-pci.h>
#include <asm/rtas.h>

#undef DEBUG

/** Overview:
 *  EEH, or "Extended Error Handling" is a PCI bridge technology for
 *  dealing with PCI bus errors that can't be dealt with within the
 *  usual PCI framework, except by check-stopping the CPU.  Systems
 *  that are designed for high-availability/reliability cannot afford
 *  to crash due to a "mere" PCI error, thus the need for EEH.
 *  An EEH-capable bridge operates by converting a detected error
 *  into a "slot freeze", taking the PCI adapter off-line, making
 *  the slot behave, from the OS'es point of view, as if the slot
 *  were "empty": all reads return 0xff's and all writes are silently
 *  ignored.  EEH slot isolation events can be triggered by parity
 *  errors on the address or data busses (e.g. during posted writes),
 *  which in turn might be caused by low voltage on the bus, dust,
 *  vibration, humidity, radioactivity or plain-old failed hardware.
 *
 *  Note, however, that one of the leading causes of EEH slot
 *  freeze events are buggy device drivers, buggy device microcode,
 *  or buggy device hardware.  This is because any attempt by the
 *  device to bus-master data to a memory address that is not
 *  assigned to the device will trigger a slot freeze.   (The idea
 *  is to prevent devices-gone-wild from corrupting system memory).
 *  Buggy hardware/drivers will have a miserable time co-existing
 *  with EEH.
 *
 *  Ideally, a PCI device driver, when suspecting that an isolation
 *  event has occured (e.g. by reading 0xff's), will then ask EEH
 *  whether this is the case, and then take appropriate steps to
 *  reset the PCI slot, the PCI device, and then resume operations.
 *  However, until that day,  the checking is done here, with the
 *  eeh_check_failure() routine embedded in the MMIO macros.  If
 *  the slot is found to be isolated, an "EEH Event" is synthesized
 *  and sent out for processing.
 */

/* If a device driver keeps reading an MMIO register in an interrupt
 * handler after a slot isolation event has occurred, we assume it
 * is broken and panic.  This sets the threshold for how many read
 * attempts we allow before panicking.
 */
#define EEH_MAX_FAILS   100000

/* RTAS tokens */
static int ibm_set_eeh_option;
static int ibm_set_slot_reset;
static int ibm_read_slot_reset_state;
static int ibm_read_slot_reset_state2;
static int ibm_slot_error_detail;
static int ibm_get_config_addr_info;
static int ibm_configure_bridge;

int eeh_subsystem_enabled;
EXPORT_SYMBOL(eeh_subsystem_enabled);

/* Lock to avoid races due to multiple reports of an error */
static DEFINE_SPINLOCK(confirm_error_lock);

/* Buffer for reporting slot-error-detail rtas calls */
static unsigned char slot_errbuf[RTAS_ERROR_LOG_MAX];
static DEFINE_SPINLOCK(slot_errbuf_lock);
static int eeh_error_buf_size;

/* System monitoring statistics */
static unsigned long no_device;
static unsigned long no_dn;
static unsigned long no_cfg_addr;
static unsigned long ignored_check;
static unsigned long total_mmio_ffs;
static unsigned long false_positives;
static unsigned long ignored_failures;
static unsigned long slot_resets;

#define IS_BRIDGE(class_code) (((class_code)<<16) == PCI_BASE_CLASS_BRIDGE)

/* --------------------------------------------------------------- */
/* Below lies the EEH event infrastructure */

void eeh_slot_error_detail (struct pci_dn *pdn, int severity)
{
        int config_addr;
        unsigned long flags;
        int rc;

        /* Log the error with the rtas logger */
        spin_lock_irqsave(&slot_errbuf_lock, flags);
        memset(slot_errbuf, 0, eeh_error_buf_size);

        /* Use PE configuration address, if present */
        config_addr = pdn->eeh_config_addr;
        if (pdn->eeh_pe_config_addr)
                config_addr = pdn->eeh_pe_config_addr;

        rc = rtas_call(ibm_slot_error_detail,
                       8, 1, NULL, config_addr,
                       BUID_HI(pdn->phb->buid),
                       BUID_LO(pdn->phb->buid), NULL, 0,
                       virt_to_phys(slot_errbuf),
                       eeh_error_buf_size,
                       severity);

        if (rc == 0)
                log_error(slot_errbuf, ERR_TYPE_RTAS_LOG, 0);
        spin_unlock_irqrestore(&slot_errbuf_lock, flags);
}

/**
 * read_slot_reset_state - Read the reset state of a device node's slot
 * @dn: device node to read
 * @rets: array to return results in
 */
static int read_slot_reset_state(struct pci_dn *pdn, int rets[])
{
        int token, outputs;
        int config_addr;

        if (ibm_read_slot_reset_state2 != RTAS_UNKNOWN_SERVICE) {
                token = ibm_read_slot_reset_state2;
                outputs = 4;
        } else {
                token = ibm_read_slot_reset_state;
                rets[2] = 0; /* fake PE Unavailable info */
                outputs = 3;
        }

        /* Use PE configuration address, if present */
        config_addr = pdn->eeh_config_addr;
        if (pdn->eeh_pe_config_addr)
                config_addr = pdn->eeh_pe_config_addr;

        return rtas_call(token, 3, outputs, rets, config_addr,
                         BUID_HI(pdn->phb->buid), BUID_LO(pdn->phb->buid));
}

/**
 * eeh_token_to_phys - convert EEH address token to phys address
 * @token i/o token, should be address in the form 0xA....
 */
static inline unsigned long eeh_token_to_phys(unsigned long token)
{
        pte_t *ptep;
        unsigned long pa;

        ptep = find_linux_pte(init_mm.pgd, token);
        if (!ptep)
                return token;
        pa = pte_pfn(*ptep) << PAGE_SHIFT;

        return pa | (token & (PAGE_SIZE-1));
}

/** 
 * Return the "partitionable endpoint" (pe) under which this device lies
 */
struct device_node * find_device_pe(struct device_node *dn)
{
        while ((dn->parent) && PCI_DN(dn->parent) &&
              (PCI_DN(dn->parent)->eeh_mode & EEH_MODE_SUPPORTED)) {
                dn = dn->parent;
        }
        return dn;
}

/** Mark all devices that are peers of this device as failed.
 *  Mark the device driver too, so that it can see the failure
 *  immediately; this is critical, since some drivers poll
 *  status registers in interrupts ... If a driver is polling,
 *  and the slot is frozen, then the driver can deadlock in
 *  an interrupt context, which is bad.
 */

static void __eeh_mark_slot (struct device_node *dn, int mode_flag)
{
        while (dn) {
                if (PCI_DN(dn)) {
                        /* Mark the pci device driver too */
                        struct pci_dev *dev = PCI_DN(dn)->pcidev;

                        PCI_DN(dn)->eeh_mode |= mode_flag;

                        if (dev && dev->driver)
                                dev->error_state = pci_channel_io_frozen;

                        if (dn->child)
                                __eeh_mark_slot (dn->child, mode_flag);
                }
                dn = dn->sibling;
        }
}

void eeh_mark_slot (struct device_node *dn, int mode_flag)
{
        struct pci_dev *dev;
        dn = find_device_pe (dn);

        /* Back up one, since config addrs might be shared */
        if (PCI_DN(dn) && PCI_DN(dn)->eeh_pe_config_addr)
                dn = dn->parent;

        PCI_DN(dn)->eeh_mode |= mode_flag;

        /* Mark the pci device too */
        dev = PCI_DN(dn)->pcidev;
        if (dev)
                dev->error_state = pci_channel_io_frozen;

        __eeh_mark_slot (dn->child, mode_flag);
}

static void __eeh_clear_slot (struct device_node *dn, int mode_flag)
{
        while (dn) {
                if (PCI_DN(dn)) {
                        PCI_DN(dn)->eeh_mode &= ~mode_flag;
                        PCI_DN(dn)->eeh_check_count = 0;
                        if (dn->child)
                                __eeh_clear_slot (dn->child, mode_flag);
                }
                dn = dn->sibling;
        }
}

void eeh_clear_slot (struct device_node *dn, int mode_flag)
{
        unsigned long flags;
        spin_lock_irqsave(&confirm_error_lock, flags);
        
        dn = find_device_pe (dn);
        
        /* Back up one, since config addrs might be shared */
        if (PCI_DN(dn) && PCI_DN(dn)->eeh_pe_config_addr)
                dn = dn->parent;

        PCI_DN(dn)->eeh_mode &= ~mode_flag;
        PCI_DN(dn)->eeh_check_count = 0;
        __eeh_clear_slot (dn->child, mode_flag);
        spin_unlock_irqrestore(&confirm_error_lock, flags);
}

/**
 * eeh_dn_check_failure - check if all 1's data is due to EEH slot freeze
 * @dn device node
 * @dev pci device, if known
 *
 * Check for an EEH failure for the given device node.  Call this
 * routine if the result of a read was all 0xff's and you want to
 * find out if this is due to an EEH slot freeze.  This routine
 * will query firmware for the EEH status.
 *
 * Returns 0 if there has not been an EEH error; otherwise returns
 * a non-zero value and queues up a slot isolation event notification.
 *
 * It is safe to call this routine in an interrupt context.
 */
int eeh_dn_check_failure(struct device_node *dn, struct pci_dev *dev)
{
        int ret;
        int rets[3];
        unsigned long flags;
        struct pci_dn *pdn;
        enum pci_channel_state state;
        int rc = 0;

        total_mmio_ffs++;

        if (!eeh_subsystem_enabled)
                return 0;

        if (!dn) {
                no_dn++;
                return 0;
        }
        pdn = PCI_DN(dn);

        /* Access to IO BARs might get this far and still not want checking. */
        if (!(pdn->eeh_mode & EEH_MODE_SUPPORTED) ||
            pdn->eeh_mode & EEH_MODE_NOCHECK) {
                ignored_check++;
#ifdef DEBUG
                printk ("EEH:ignored check (%x) for %s %s\n", 
                        pdn->eeh_mode, pci_name (dev), dn->full_name);
#endif
                return 0;
        }

        if (!pdn->eeh_config_addr && !pdn->eeh_pe_config_addr) {
                no_cfg_addr++;
                return 0;
        }

        /* If we already have a pending isolation event for this
         * slot, we know it's bad already, we don't need to check.
         * Do this checking under a lock; as multiple PCI devices
         * in one slot might report errors simultaneously, and we
         * only want one error recovery routine running.
         */
        spin_lock_irqsave(&confirm_error_lock, flags);
        rc = 1;
        if (pdn->eeh_mode & EEH_MODE_ISOLATED) {
                pdn->eeh_check_count ++;
                if (pdn->eeh_check_count >= EEH_MAX_FAILS) {
                        printk (KERN_ERR "EEH: Device driver ignored %d bad reads, panicing\n",
                                pdn->eeh_check_count);
                        dump_stack();
                        msleep(5000);
                        
                        /* re-read the slot reset state */
                        if (read_slot_reset_state(pdn, rets) != 0)
                                rets[0] = -1;   /* reset state unknown */

                        /* If we are here, then we hit an infinite loop. Stop. */
                        panic("EEH: MMIO halt (%d) on device:%s\n", rets[0], pci_name(dev));
                }
                goto dn_unlock;
        }

        /*
         * Now test for an EEH failure.  This is VERY expensive.
         * Note that the eeh_config_addr may be a parent device
         * in the case of a device behind a bridge, or it may be
         * function zero of a multi-function device.
         * In any case they must share a common PHB.
         */
        ret = read_slot_reset_state(pdn, rets);

        /* If the call to firmware failed, punt */
        if (ret != 0) {
                printk(KERN_WARNING "EEH: read_slot_reset_state() failed; rc=%d dn=%s\n",
                       ret, dn->full_name);
                false_positives++;
                rc = 0;
                goto dn_unlock;
        }

        /* If EEH is not supported on this device, punt. */
        if (rets[1] != 1) {
                printk(KERN_WARNING "EEH: event on unsupported device, rc=%d dn=%s\n",
                       ret, dn->full_name);
                false_positives++;
                rc = 0;
                goto dn_unlock;
        }

        /* If not the kind of error we know about, punt. */
        if (rets[0] != 2 && rets[0] != 4 && rets[0] != 5) {
                false_positives++;
                rc = 0;
                goto dn_unlock;
        }

        /* Note that config-io to empty slots may fail;
         * we recognize empty because they don't have children. */
        if ((rets[0] == 5) && (dn->child == NULL)) {
                false_positives++;
                rc = 0;
                goto dn_unlock;
        }

        slot_resets++;
 
        /* Avoid repeated reports of this failure, including problems
         * with other functions on this device, and functions under
         * bridges. */
        eeh_mark_slot (dn, EEH_MODE_ISOLATED);
        spin_unlock_irqrestore(&confirm_error_lock, flags);

        state = pci_channel_io_normal;
        if ((rets[0] == 2) || (rets[0] == 4))
                state = pci_channel_io_frozen;
        if (rets[0] == 5)
                state = pci_channel_io_perm_failure;
        eeh_send_failure_event (dn, dev, state, rets[2]);

        /* Most EEH events are due to device driver bugs.  Having
         * a stack trace will help the device-driver authors figure
         * out what happened.  So print that out. */
        if (rets[0] != 5) dump_stack();
        return 1;

dn_unlock:
        spin_unlock_irqrestore(&confirm_error_lock, flags);
        return rc;
}

EXPORT_SYMBOL_GPL(eeh_dn_check_failure);

/**
 * eeh_check_failure - check if all 1's data is due to EEH slot freeze
 * @token i/o token, should be address in the form 0xA....
 * @val value, should be all 1's (XXX why do we need this arg??)
 *
 * Check for an EEH failure at the given token address.  Call this
 * routine if the result of a read was all 0xff's and you want to
 * find out if this is due to an EEH slot freeze event.  This routine
 * will query firmware for the EEH status.
 *
 * Note this routine is safe to call in an interrupt context.
 */
unsigned long eeh_check_failure(const volatile void __iomem *token, unsigned long val)
{
        unsigned long addr;
        struct pci_dev *dev;
        struct device_node *dn;

        /* Finding the phys addr + pci device; this is pretty quick. */
        addr = eeh_token_to_phys((unsigned long __force) token);
        dev = pci_get_device_by_addr(addr);
        if (!dev) {
                no_device++;
                return val;
        }

        dn = pci_device_to_OF_node(dev);
        eeh_dn_check_failure (dn, dev);

        pci_dev_put(dev);
        return val;
}

EXPORT_SYMBOL(eeh_check_failure);

/* ------------------------------------------------------------- */
/* The code below deals with error recovery */

/**
 * eeh_slot_availability - returns error status of slot
 * @pdn pci device node
 *
 * Return negative value if a permanent error, else return
 * a number of milliseconds to wait until the PCI slot is
 * ready to be used.
 */
static int
eeh_slot_availability(struct pci_dn *pdn)
{
        int rc;
        int rets[3];

        rc = read_slot_reset_state(pdn, rets);

        if (rc) return rc;

        if (rets[1] == 0) return -1;  /* EEH is not supported */
        if (rets[0] == 0) return 0;   /* Oll Korrect */
        if (rets[0] == 5) {
                if (rets[2] == 0) return -1; /* permanently unavailable */
                return rets[2]; /* number of millisecs to wait */
        }
        if (rets[0] == 1)
                return 250;

        printk (KERN_ERR "EEH: Slot unavailable: rc=%d, rets=%d %d %d\n",
                rc, rets[0], rets[1], rets[2]);
        return -2;
}

/**
 * rtas_pci_enable - enable MMIO or DMA transfers for this slot
 * @pdn pci device node
 */

int
rtas_pci_enable(struct pci_dn *pdn, int function)
{
        int config_addr;
        int rc;

        /* Use PE configuration address, if present */
        config_addr = pdn->eeh_config_addr;
        if (pdn->eeh_pe_config_addr)
                config_addr = pdn->eeh_pe_config_addr;

        rc = rtas_call(ibm_set_eeh_option, 4, 1, NULL,
                       config_addr,
                       BUID_HI(pdn->phb->buid),
                       BUID_LO(pdn->phb->buid),
                            function);

        if (rc)
                printk(KERN_WARNING "EEH: Cannot enable function %d, err=%d dn=%s\n",
                        function, rc, pdn->node->full_name);

        return rc;
}

/**
 * rtas_pci_slot_reset - raises/lowers the pci #RST line
 * @pdn pci device node
 * @state: 1/0 to raise/lower the #RST
 *
 * Clear the EEH-frozen condition on a slot.  This routine
 * asserts the PCI #RST line if the 'state' argument is '1',
 * and drops the #RST line if 'state is '0'.  This routine is
 * safe to call in an interrupt context.
 *
 */

static void
rtas_pci_slot_reset(struct pci_dn *pdn, int state)
{
        int config_addr;
        int rc;

        BUG_ON (pdn==NULL); 

        if (!pdn->phb) {
                printk (KERN_WARNING "EEH: in slot reset, device node %s has no phb\n",
                        pdn->node->full_name);
                return;
        }

        /* Use PE configuration address, if present */
        config_addr = pdn->eeh_config_addr;
        if (pdn->eeh_pe_config_addr)
                config_addr = pdn->eeh_pe_config_addr;

        rc = rtas_call(ibm_set_slot_reset,4,1, NULL,
                       config_addr,
                       BUID_HI(pdn->phb->buid),
                       BUID_LO(pdn->phb->buid),
                       state);
        if (rc)
                printk (KERN_WARNING "EEH: Unable to reset the failed slot,"
                        " (%d) #RST=%d dn=%s\n",
                        rc, state, pdn->node->full_name);
}

/**
 * rtas_set_slot_reset -- assert the pci #RST line for 1/4 second
 * @pdn: pci device node to be reset.
 *
 *  Return 0 if success, else a non-zero value.
 */

static void __rtas_set_slot_reset(struct pci_dn *pdn)
{
        rtas_pci_slot_reset (pdn, 1);

        /* The PCI bus requires that the reset be held high for at least
         * a 100 milliseconds. We wait a bit longer 'just in case'.  */

#define PCI_BUS_RST_HOLD_TIME_MSEC 250
        msleep (PCI_BUS_RST_HOLD_TIME_MSEC);
        
        /* We might get hit with another EEH freeze as soon as the 
         * pci slot reset line is dropped. Make sure we don't miss
         * these, and clear the flag now. */
        eeh_clear_slot (pdn->node, EEH_MODE_ISOLATED);

        rtas_pci_slot_reset (pdn, 0);

        /* After a PCI slot has been reset, the PCI Express spec requires
         * a 1.5 second idle time for the bus to stabilize, before starting
         * up traffic. */
#define PCI_BUS_SETTLE_TIME_MSEC 1800
        msleep (PCI_BUS_SETTLE_TIME_MSEC);
}

int rtas_set_slot_reset(struct pci_dn *pdn)
{
        int i, rc;

        __rtas_set_slot_reset(pdn);

        /* Now double check with the firmware to make sure the device is
         * ready to be used; if not, wait for recovery. */
        for (i=0; i<10; i++) {
                rc = eeh_slot_availability (pdn);
                if (rc == 0)
                        return 0;

                if (rc == -2) {
                        printk (KERN_ERR "EEH: failed (%d) to reset slot %s\n",
                                i, pdn->node->full_name);
                        __rtas_set_slot_reset(pdn);
                        continue;
                }

                if (rc < 0) {
                        printk (KERN_ERR "EEH: unrecoverable slot failure %s\n",
                                pdn->node->full_name);
                        return -1;
                }

                msleep (rc+100);
        }

        rc = eeh_slot_availability (pdn);
        if (rc)
                printk (KERN_ERR "EEH: timeout resetting slot %s\n", pdn->node->full_name);

        return rc;
}

/* ------------------------------------------------------- */
/** Save and restore of PCI BARs
 *
 * Although firmware will set up BARs during boot, it doesn't
 * set up device BAR's after a device reset, although it will,
 * if requested, set up bridge configuration. Thus, we need to
 * configure the PCI devices ourselves.  
 */

/**
 * __restore_bars - Restore the Base Address Registers
 * @pdn: pci device node
 *
 * Loads the PCI configuration space base address registers,
 * the expansion ROM base address, the latency timer, and etc.
 * from the saved values in the device node.
 */
static inline void __restore_bars (struct pci_dn *pdn)
{
        int i;

        if (NULL==pdn->phb) return;
        for (i=4; i<10; i++) {
                rtas_write_config(pdn, i*4, 4, pdn->config_space[i]);
        }

        /* 12 == Expansion ROM Address */
        rtas_write_config(pdn, 12*4, 4, pdn->config_space[12]);

#define BYTE_SWAP(OFF) (8*((OFF)/4)+3-(OFF))
#define SAVED_BYTE(OFF) (((u8 *)(pdn->config_space))[BYTE_SWAP(OFF)])

        rtas_write_config (pdn, PCI_CACHE_LINE_SIZE, 1,
                    SAVED_BYTE(PCI_CACHE_LINE_SIZE));

        rtas_write_config (pdn, PCI_LATENCY_TIMER, 1,
                    SAVED_BYTE(PCI_LATENCY_TIMER));

        /* max latency, min grant, interrupt pin and line */
        rtas_write_config(pdn, 15*4, 4, pdn->config_space[15]);
}

/**
 * eeh_restore_bars - restore the PCI config space info
 *
 * This routine performs a recursive walk to the children
 * of this device as well.
 */
void eeh_restore_bars(struct pci_dn *pdn)
{
        struct device_node *dn;
        if (!pdn) 
                return;
        
        if ((pdn->eeh_mode & EEH_MODE_SUPPORTED) && !IS_BRIDGE(pdn->class_code))
                __restore_bars (pdn);

        dn = pdn->node->child;
        while (dn) {
                eeh_restore_bars (PCI_DN(dn));
                dn = dn->sibling;
        }
}

/**
 * eeh_save_bars - save device bars
 *
 * Save the values of the device bars. Unlike the restore
 * routine, this routine is *not* recursive. This is because
 * PCI devices are added individuallly; but, for the restore,
 * an entire slot is reset at a time.
 */
static void eeh_save_bars(struct pci_dn *pdn)
{
        int i;

        if (!pdn )
                return;
        
        for (i = 0; i < 16; i++)
                rtas_read_config(pdn, i * 4, 4, &pdn->config_space[i]);
}

void
rtas_configure_bridge(struct pci_dn *pdn)
{
        int config_addr;
        int rc;

        /* Use PE configuration address, if present */
        config_addr = pdn->eeh_config_addr;
        if (pdn->eeh_pe_config_addr)
                config_addr = pdn->eeh_pe_config_addr;

        rc = rtas_call(ibm_configure_bridge,3,1, NULL,
                       config_addr,
                       BUID_HI(pdn->phb->buid),
                       BUID_LO(pdn->phb->buid));
        if (rc) {
                printk (KERN_WARNING "EEH: Unable to configure device bridge (%d) for %s\n",
                        rc, pdn->node->full_name);
        }
}

/* ------------------------------------------------------------- */
/* The code below deals with enabling EEH for devices during  the
 * early boot sequence.  EEH must be enabled before any PCI probing
 * can be done.
 */

#define EEH_ENABLE 1

struct eeh_early_enable_info {
        unsigned int buid_hi;
        unsigned int buid_lo;
};

/* Enable eeh for the given device node. */
static void *early_enable_eeh(struct device_node *dn, void *data)
{
        unsigned int rets[3];
        struct eeh_early_enable_info *info = data;
        int ret;
        const char *status = get_property(dn, "status", NULL);
        const u32 *class_code = get_property(dn, "class-code", NULL);
        const u32 *vendor_id = get_property(dn, "vendor-id", NULL);
        const u32 *device_id = get_property(dn, "device-id", NULL);
        const u32 *regs;
        int enable;
        struct pci_dn *pdn = PCI_DN(dn);

        pdn->class_code = 0;
        pdn->eeh_mode = 0;
        pdn->eeh_check_count = 0;
        pdn->eeh_freeze_count = 0;

        if (status && strcmp(status, "ok") != 0)
                return NULL;    /* ignore devices with bad status */

        /* Ignore bad nodes. */
        if (!class_code || !vendor_id || !device_id)
                return NULL;

        /* There is nothing to check on PCI to ISA bridges */
        if (dn->type && !strcmp(dn->type, "isa")) {
                pdn->eeh_mode |= EEH_MODE_NOCHECK;
                return NULL;
        }
        pdn->class_code = *class_code;

        /*
         * Now decide if we are going to "Disable" EEH checking
         * for this device.  We still run with the EEH hardware active,
         * but we won't be checking for ff's.  This means a driver
         * could return bad data (very bad!), an interrupt handler could
         * hang waiting on status bits that won't change, etc.
         * But there are a few cases like display devices that make sense.
         */
        enable = 1;     /* i.e. we will do checking */
#if 0
        if ((*class_code >> 16) == PCI_BASE_CLASS_DISPLAY)
                enable = 0;
#endif

        if (!enable)
                pdn->eeh_mode |= EEH_MODE_NOCHECK;

        /* Ok... see if this device supports EEH.  Some do, some don't,
         * and the only way to find out is to check each and every one. */
        regs = get_property(dn, "reg", NULL);
        if (regs) {
                /* First register entry is addr (00BBSS00)  */
                /* Try to enable eeh */
                ret = rtas_call(ibm_set_eeh_option, 4, 1, NULL,
                                regs[0], info->buid_hi, info->buid_lo,
                                EEH_ENABLE);

                enable = 0;
                if (ret == 0) {
                        pdn->eeh_config_addr = regs[0];

                        /* If the newer, better, ibm,get-config-addr-info is supported, 
                         * then use that instead. */
                        pdn->eeh_pe_config_addr = 0;
                        if (ibm_get_config_addr_info != RTAS_UNKNOWN_SERVICE) {
                                ret = rtas_call (ibm_get_config_addr_info, 4, 2, rets, 
                                        pdn->eeh_config_addr, 
                                        info->buid_hi, info->buid_lo,
                                        0);
                                if (ret == 0)
                                        pdn->eeh_pe_config_addr = rets[0];
                        }

                        /* Some older systems (Power4) allow the
                         * ibm,set-eeh-option call to succeed even on nodes
                         * where EEH is not supported. Verify support
                         * explicitly. */
                        ret = read_slot_reset_state(pdn, rets);
                        if ((ret == 0) && (rets[1] == 1))
                                enable = 1;
                }

                if (enable) {
                        eeh_subsystem_enabled = 1;
                        pdn->eeh_mode |= EEH_MODE_SUPPORTED;

#ifdef DEBUG
                        printk(KERN_DEBUG "EEH: %s: eeh enabled, config=%x pe_config=%x\n",
                               dn->full_name, pdn->eeh_config_addr, pdn->eeh_pe_config_addr);
#endif
                } else {

                        /* This device doesn't support EEH, but it may have an
                         * EEH parent, in which case we mark it as supported. */
                        if (dn->parent && PCI_DN(dn->parent)
                            && (PCI_DN(dn->parent)->eeh_mode & EEH_MODE_SUPPORTED)) {
                                /* Parent supports EEH. */
                                pdn->eeh_mode |= EEH_MODE_SUPPORTED;
                                pdn->eeh_config_addr = PCI_DN(dn->parent)->eeh_config_addr;
                                return NULL;
                        }
                }
        } else {
                printk(KERN_WARNING "EEH: %s: unable to get reg property.\n",
                       dn->full_name);
        }

        eeh_save_bars(pdn);
        return NULL;
}

/*
 * Initialize EEH by trying to enable it for all of the adapters in the system.
 * As a side effect we can determine here if eeh is supported at all.
 * Note that we leave EEH on so failed config cycles won't cause a machine
 * check.  If a user turns off EEH for a particular adapter they are really
 * telling Linux to ignore errors.  Some hardware (e.g. POWER5) won't
 * grant access to a slot if EEH isn't enabled, and so we always enable
 * EEH for all slots/all devices.
 *
 * The eeh-force-off option disables EEH checking globally, for all slots.
 * Even if force-off is set, the EEH hardware is still enabled, so that
 * newer systems can boot.
 */
void __init eeh_init(void)
{
        struct device_node *phb, *np;
        struct eeh_early_enable_info info;

        spin_lock_init(&confirm_error_lock);
        spin_lock_init(&slot_errbuf_lock);

        np = of_find_node_by_path("/rtas");
        if (np == NULL)
                return;

        ibm_set_eeh_option = rtas_token("ibm,set-eeh-option");
        ibm_set_slot_reset = rtas_token("ibm,set-slot-reset");
        ibm_read_slot_reset_state2 = rtas_token("ibm,read-slot-reset-state2");
        ibm_read_slot_reset_state = rtas_token("ibm,read-slot-reset-state");
        ibm_slot_error_detail = rtas_token("ibm,slot-error-detail");
        ibm_get_config_addr_info = rtas_token("ibm,get-config-addr-info");
        ibm_configure_bridge = rtas_token ("ibm,configure-bridge");

        if (ibm_set_eeh_option == RTAS_UNKNOWN_SERVICE)
                return;

        eeh_error_buf_size = rtas_token("rtas-error-log-max");
        if (eeh_error_buf_size == RTAS_UNKNOWN_SERVICE) {
                eeh_error_buf_size = 1024;
        }
        if (eeh_error_buf_size > RTAS_ERROR_LOG_MAX) {
                printk(KERN_WARNING "EEH: rtas-error-log-max is bigger than allocated "
                      "buffer ! (%d vs %d)", eeh_error_buf_size, RTAS_ERROR_LOG_MAX);
                eeh_error_buf_size = RTAS_ERROR_LOG_MAX;
        }

        /* Enable EEH for all adapters.  Note that eeh requires buid's */
        for (phb = of_find_node_by_name(NULL, "pci"); phb;
             phb = of_find_node_by_name(phb, "pci")) {
                unsigned long buid;

                buid = get_phb_buid(phb);
                if (buid == 0 || PCI_DN(phb) == NULL)
                        continue;

                info.buid_lo = BUID_LO(buid);
                info.buid_hi = BUID_HI(buid);
                traverse_pci_devices(phb, early_enable_eeh, &info);
        }

        if (eeh_subsystem_enabled)
                printk(KERN_INFO "EEH: PCI Enhanced I/O Error Handling Enabled\n");
        else
                printk(KERN_WARNING "EEH: No capable adapters found\n");
}

/**
 * eeh_add_device_early - enable EEH for the indicated device_node
 * @dn: device node for which to set up EEH
 *
 * This routine must be used to perform EEH initialization for PCI
 * devices that were added after system boot (e.g. hotplug, dlpar).
 * This routine must be called before any i/o is performed to the
 * adapter (inluding any config-space i/o).
 * Whether this actually enables EEH or not for this device depends
 * on the CEC architecture, type of the device, on earlier boot
 * command-line arguments & etc.
 */
static void eeh_add_device_early(struct device_node *dn)
{
        struct pci_controller *phb;
        struct eeh_early_enable_info info;

        if (!dn || !PCI_DN(dn))
                return;
        phb = PCI_DN(dn)->phb;

        /* USB Bus children of PCI devices will not have BUID's */
        if (NULL == phb || 0 == phb->buid)
                return;

        info.buid_hi = BUID_HI(phb->buid);
        info.buid_lo = BUID_LO(phb->buid);
        early_enable_eeh(dn, &info);
}

void eeh_add_device_tree_early(struct device_node *dn)
{
        struct device_node *sib;
        for (sib = dn->child; sib; sib = sib->sibling)
                eeh_add_device_tree_early(sib);
        eeh_add_device_early(dn);
}
EXPORT_SYMBOL_GPL(eeh_add_device_tree_early);

/**
 * eeh_add_device_late - perform EEH initialization for the indicated pci device
 * @dev: pci device for which to set up EEH
 *
 * This routine must be used to complete EEH initialization for PCI
 * devices that were added after system boot (e.g. hotplug, dlpar).
 */
static void eeh_add_device_late(struct pci_dev *dev)
{
        struct device_node *dn;
        struct pci_dn *pdn;

        if (!dev || !eeh_subsystem_enabled)
                return;

#ifdef DEBUG
        printk(KERN_DEBUG "EEH: adding device %s\n", pci_name(dev));
#endif

        pci_dev_get (dev);
        dn = pci_device_to_OF_node(dev);
        pdn = PCI_DN(dn);
        pdn->pcidev = dev;

        pci_addr_cache_insert_device (dev);
}

void eeh_add_device_tree_late(struct pci_bus *bus)
{
        struct pci_dev *dev;

        list_for_each_entry(dev, &bus->devices, bus_list) {
                eeh_add_device_late(dev);
                if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                        struct pci_bus *subbus = dev->subordinate;
                        if (subbus)
                                eeh_add_device_tree_late(subbus);
                }
        }
}
EXPORT_SYMBOL_GPL(eeh_add_device_tree_late);

/**
 * eeh_remove_device - undo EEH setup for the indicated pci device
 * @dev: pci device to be removed
 *
 * This routine should be called when a device is removed from
 * a running system (e.g. by hotplug or dlpar).  It unregisters
 * the PCI device from the EEH subsystem.  I/O errors affecting
 * this device will no longer be detected after this call; thus,
 * i/o errors affecting this slot may leave this device unusable.
 */
static void eeh_remove_device(struct pci_dev *dev)
{
        struct device_node *dn;
        if (!dev || !eeh_subsystem_enabled)
                return;

        /* Unregister the device with the EEH/PCI address search system */
#ifdef DEBUG
        printk(KERN_DEBUG "EEH: remove device %s\n", pci_name(dev));
#endif
        pci_addr_cache_remove_device(dev);

        dn = pci_device_to_OF_node(dev);
        if (PCI_DN(dn)->pcidev) {
                PCI_DN(dn)->pcidev = NULL;
                pci_dev_put (dev);
        }
}

void eeh_remove_bus_device(struct pci_dev *dev)
{
        struct pci_bus *bus = dev->subordinate;
        struct pci_dev *child, *tmp;

        eeh_remove_device(dev);

        if (bus && dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                list_for_each_entry_safe(child, tmp, &bus->devices, bus_list)
                         eeh_remove_bus_device(child);
        }
}
EXPORT_SYMBOL_GPL(eeh_remove_bus_device);

static int proc_eeh_show(struct seq_file *m, void *v)
{
        if (0 == eeh_subsystem_enabled) {
                seq_printf(m, "EEH Subsystem is globally disabled\n");
                seq_printf(m, "eeh_total_mmio_ffs=%ld\n", total_mmio_ffs);
        } else {
                seq_printf(m, "EEH Subsystem is enabled\n");
                seq_printf(m,
                                "no device=%ld\n"
                                "no device node=%ld\n"
                                "no config address=%ld\n"
                                "check not wanted=%ld\n"
                                "eeh_total_mmio_ffs=%ld\n"
                                "eeh_false_positives=%ld\n"
                                "eeh_ignored_failures=%ld\n"
                                "eeh_slot_resets=%ld\n",
                                no_device, no_dn, no_cfg_addr, 
                                ignored_check, total_mmio_ffs, 
                                false_positives, ignored_failures, 
                                slot_resets);
        }

        return 0;
}

static int proc_eeh_open(struct inode *inode, struct file *file)
{
        return single_open(file, proc_eeh_show, NULL);
}

static const struct file_operations proc_eeh_operations = {
        .open      = proc_eeh_open,
        .read      = seq_read,
        .llseek    = seq_lseek,
        .release   = single_release,
};

static int __init eeh_init_proc(void)
{
        struct proc_dir_entry *e;

        if (machine_is(pseries)) {
                e = create_proc_entry("ppc64/eeh", 0, NULL);
                if (e)
                        e->proc_fops = &proc_eeh_operations;
        }

        return 0;
}
__initcall(eeh_init_proc);