[PATCH] ppc64: PCI error rate statistics

[linux-2.6] / arch / ppc64 / kernel / 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/init.h>
#include <linux/list.h>
#include <linux/notifier.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/io.h>
#include <asm/machdep.h>
#include <asm/rtas.h>
#include <asm/atomic.h>
#include <asm/systemcfg.h>
#include <asm/ppc-pci.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.
 */

/* EEH event workqueue setup. */
static DEFINE_SPINLOCK(eeh_eventlist_lock);
LIST_HEAD(eeh_eventlist);
static void eeh_event_handler(void *);
DECLARE_WORK(eeh_event_wq, eeh_event_handler, NULL);

static struct notifier_block *eeh_notifier_chain;

/*
 * 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   1000
static atomic_t eeh_fail_count;

/* 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 eeh_subsystem_enabled;

/* 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 DEFINE_PER_CPU(unsigned long, no_device);
static DEFINE_PER_CPU(unsigned long, no_dn);
static DEFINE_PER_CPU(unsigned long, no_cfg_addr);
static DEFINE_PER_CPU(unsigned long, ignored_check);
static DEFINE_PER_CPU(unsigned long, total_mmio_ffs);
static DEFINE_PER_CPU(unsigned long, false_positives);
static DEFINE_PER_CPU(unsigned long, ignored_failures);
static DEFINE_PER_CPU(unsigned long, slot_resets);

/**
 * The pci address cache subsystem.  This subsystem places
 * PCI device address resources into a red-black tree, sorted
 * according to the address range, so that given only an i/o
 * address, the corresponding PCI device can be **quickly**
 * found. It is safe to perform an address lookup in an interrupt
 * context; this ability is an important feature.
 *
 * Currently, the only customer of this code is the EEH subsystem;
 * thus, this code has been somewhat tailored to suit EEH better.
 * In particular, the cache does *not* hold the addresses of devices
 * for which EEH is not enabled.
 *
 * (Implementation Note: The RB tree seems to be better/faster
 * than any hash algo I could think of for this problem, even
 * with the penalty of slow pointer chases for d-cache misses).
 */
struct pci_io_addr_range
{
        struct rb_node rb_node;
        unsigned long addr_lo;
        unsigned long addr_hi;
        struct pci_dev *pcidev;
        unsigned int flags;
};

static struct pci_io_addr_cache
{
        struct rb_root rb_root;
        spinlock_t piar_lock;
} pci_io_addr_cache_root;

static inline struct pci_dev *__pci_get_device_by_addr(unsigned long addr)
{
        struct rb_node *n = pci_io_addr_cache_root.rb_root.rb_node;

        while (n) {
                struct pci_io_addr_range *piar;
                piar = rb_entry(n, struct pci_io_addr_range, rb_node);

                if (addr < piar->addr_lo) {
                        n = n->rb_left;
                } else {
                        if (addr > piar->addr_hi) {
                                n = n->rb_right;
                        } else {
                                pci_dev_get(piar->pcidev);
                                return piar->pcidev;
                        }
                }
        }

        return NULL;
}

/**
 * pci_get_device_by_addr - Get device, given only address
 * @addr: mmio (PIO) phys address or i/o port number
 *
 * Given an mmio phys address, or a port number, find a pci device
 * that implements this address.  Be sure to pci_dev_put the device
 * when finished.  I/O port numbers are assumed to be offset
 * from zero (that is, they do *not* have pci_io_addr added in).
 * It is safe to call this function within an interrupt.
 */
static struct pci_dev *pci_get_device_by_addr(unsigned long addr)
{
        struct pci_dev *dev;
        unsigned long flags;

        spin_lock_irqsave(&pci_io_addr_cache_root.piar_lock, flags);
        dev = __pci_get_device_by_addr(addr);
        spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags);
        return dev;
}

#ifdef DEBUG
/*
 * Handy-dandy debug print routine, does nothing more
 * than print out the contents of our addr cache.
 */
static void pci_addr_cache_print(struct pci_io_addr_cache *cache)
{
        struct rb_node *n;
        int cnt = 0;

        n = rb_first(&cache->rb_root);
        while (n) {
                struct pci_io_addr_range *piar;
                piar = rb_entry(n, struct pci_io_addr_range, rb_node);
                printk(KERN_DEBUG "PCI: %s addr range %d [%lx-%lx]: %s\n",
                       (piar->flags & IORESOURCE_IO) ? "i/o" : "mem", cnt,
                       piar->addr_lo, piar->addr_hi, pci_name(piar->pcidev));
                cnt++;
                n = rb_next(n);
        }
}
#endif

/* Insert address range into the rb tree. */
static struct pci_io_addr_range *
pci_addr_cache_insert(struct pci_dev *dev, unsigned long alo,
                      unsigned long ahi, unsigned int flags)
{
        struct rb_node **p = &pci_io_addr_cache_root.rb_root.rb_node;
        struct rb_node *parent = NULL;
        struct pci_io_addr_range *piar;

        /* Walk tree, find a place to insert into tree */
        while (*p) {
                parent = *p;
                piar = rb_entry(parent, struct pci_io_addr_range, rb_node);
                if (ahi < piar->addr_lo) {
                        p = &parent->rb_left;
                } else if (alo > piar->addr_hi) {
                        p = &parent->rb_right;
                } else {
                        if (dev != piar->pcidev ||
                            alo != piar->addr_lo || ahi != piar->addr_hi) {
                                printk(KERN_WARNING "PIAR: overlapping address range\n");
                        }
                        return piar;
                }
        }
        piar = (struct pci_io_addr_range *)kmalloc(sizeof(struct pci_io_addr_range), GFP_ATOMIC);
        if (!piar)
                return NULL;

        piar->addr_lo = alo;
        piar->addr_hi = ahi;
        piar->pcidev = dev;
        piar->flags = flags;

#ifdef DEBUG
        printk(KERN_DEBUG "PIAR: insert range=[%lx:%lx] dev=%s\n",
                          alo, ahi, pci_name (dev));
#endif

        rb_link_node(&piar->rb_node, parent, p);
        rb_insert_color(&piar->rb_node, &pci_io_addr_cache_root.rb_root);

        return piar;
}

static void __pci_addr_cache_insert_device(struct pci_dev *dev)
{
        struct device_node *dn;
        struct pci_dn *pdn;
        int i;
        int inserted = 0;

        dn = pci_device_to_OF_node(dev);
        if (!dn) {
                printk(KERN_WARNING "PCI: no pci dn found for dev=%s\n", pci_name(dev));
                return;
        }

        /* Skip any devices for which EEH is not enabled. */
        pdn = PCI_DN(dn);
        if (!(pdn->eeh_mode & EEH_MODE_SUPPORTED) ||
            pdn->eeh_mode & EEH_MODE_NOCHECK) {
#ifdef DEBUG
                printk(KERN_INFO "PCI: skip building address cache for=%s - %s\n",
                       pci_name(dev), pdn->node->full_name);
#endif
                return;
        }

        /* The cache holds a reference to the device... */
        pci_dev_get(dev);

        /* Walk resources on this device, poke them into the tree */
        for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
                unsigned long start = pci_resource_start(dev,i);
                unsigned long end = pci_resource_end(dev,i);
                unsigned int flags = pci_resource_flags(dev,i);

                /* We are interested only bus addresses, not dma or other stuff */
                if (0 == (flags & (IORESOURCE_IO | IORESOURCE_MEM)))
                        continue;
                if (start == 0 || ~start == 0 || end == 0 || ~end == 0)
                         continue;
                pci_addr_cache_insert(dev, start, end, flags);
                inserted = 1;
        }

        /* If there was nothing to add, the cache has no reference... */
        if (!inserted)
                pci_dev_put(dev);
}

/**
 * pci_addr_cache_insert_device - Add a device to the address cache
 * @dev: PCI device whose I/O addresses we are interested in.
 *
 * In order to support the fast lookup of devices based on addresses,
 * we maintain a cache of devices that can be quickly searched.
 * This routine adds a device to that cache.
 */
static void pci_addr_cache_insert_device(struct pci_dev *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&pci_io_addr_cache_root.piar_lock, flags);
        __pci_addr_cache_insert_device(dev);
        spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags);
}

static inline void __pci_addr_cache_remove_device(struct pci_dev *dev)
{
        struct rb_node *n;
        int removed = 0;

restart:
        n = rb_first(&pci_io_addr_cache_root.rb_root);
        while (n) {
                struct pci_io_addr_range *piar;
                piar = rb_entry(n, struct pci_io_addr_range, rb_node);

                if (piar->pcidev == dev) {
                        rb_erase(n, &pci_io_addr_cache_root.rb_root);
                        removed = 1;
                        kfree(piar);
                        goto restart;
                }
                n = rb_next(n);
        }

        /* The cache no longer holds its reference to this device... */
        if (removed)
                pci_dev_put(dev);
}

/**
 * pci_addr_cache_remove_device - remove pci device from addr cache
 * @dev: device to remove
 *
 * Remove a device from the addr-cache tree.
 * This is potentially expensive, since it will walk
 * the tree multiple times (once per resource).
 * But so what; device removal doesn't need to be that fast.
 */
static void pci_addr_cache_remove_device(struct pci_dev *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&pci_io_addr_cache_root.piar_lock, flags);
        __pci_addr_cache_remove_device(dev);
        spin_unlock_irqrestore(&pci_io_addr_cache_root.piar_lock, flags);
}

/**
 * pci_addr_cache_build - Build a cache of I/O addresses
 *
 * Build a cache of pci i/o addresses.  This cache will be used to
 * find the pci device that corresponds to a given address.
 * This routine scans all pci busses to build the cache.
 * Must be run late in boot process, after the pci controllers
 * have been scaned for devices (after all device resources are known).
 */
void __init pci_addr_cache_build(void)
{
        struct pci_dev *dev = NULL;

        if (!eeh_subsystem_enabled)
                return;

        spin_lock_init(&pci_io_addr_cache_root.piar_lock);

        while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
                /* Ignore PCI bridges ( XXX why ??) */
                if ((dev->class >> 16) == PCI_BASE_CLASS_BRIDGE) {
                        continue;
                }
                pci_addr_cache_insert_device(dev);
        }

#ifdef DEBUG
        /* Verify tree built up above, echo back the list of addrs. */
        pci_addr_cache_print(&pci_io_addr_cache_root);
#endif
}

/* --------------------------------------------------------------- */
/* Above lies the PCI Address Cache. Below lies the EEH event infrastructure */

/**
 * eeh_register_notifier - Register to find out about EEH events.
 * @nb: notifier block to callback on events
 */
int eeh_register_notifier(struct notifier_block *nb)
{
        return notifier_chain_register(&eeh_notifier_chain, nb);
}

/**
 * eeh_unregister_notifier - Unregister to an EEH event notifier.
 * @nb: notifier block to callback on events
 */
int eeh_unregister_notifier(struct notifier_block *nb)
{
        return notifier_chain_unregister(&eeh_notifier_chain, nb);
}

/**
 * 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;

        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;
        }

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

/**
 * eeh_panic - call panic() for an eeh event that cannot be handled.
 * The philosophy of this routine is that it is better to panic and
 * halt the OS than it is to risk possible data corruption by
 * oblivious device drivers that don't know better.
 *
 * @dev pci device that had an eeh event
 * @reset_state current reset state of the device slot
 */
static void eeh_panic(struct pci_dev *dev, int reset_state)
{
        /*
         * XXX We should create a separate sysctl for this.
         *
         * Since the panic_on_oops sysctl is used to halt the system
         * in light of potential corruption, we can use it here.
         */
        if (panic_on_oops)
                panic("EEH: MMIO failure (%d) on device:%s\n", reset_state,
                      pci_name(dev));
        else {
                __get_cpu_var(ignored_failures)++;
                printk(KERN_INFO "EEH: Ignored MMIO failure (%d) on device:%s\n",
                       reset_state, pci_name(dev));
        }
}

/**
 * eeh_event_handler - dispatch EEH events.  The detection of a frozen
 * slot can occur inside an interrupt, where it can be hard to do
 * anything about it.  The goal of this routine is to pull these
 * detection events out of the context of the interrupt handler, and
 * re-dispatch them for processing at a later time in a normal context.
 *
 * @dummy - unused
 */
static void eeh_event_handler(void *dummy)
{
        unsigned long flags;
        struct eeh_event        *event;

        while (1) {
                spin_lock_irqsave(&eeh_eventlist_lock, flags);
                event = NULL;
                if (!list_empty(&eeh_eventlist)) {
                        event = list_entry(eeh_eventlist.next, struct eeh_event, list);
                        list_del(&event->list);
                }
                spin_unlock_irqrestore(&eeh_eventlist_lock, flags);
                if (event == NULL)
                        break;

                printk(KERN_INFO "EEH: MMIO failure (%d), notifiying device "
                       "%s\n", event->reset_state,
                       pci_name(event->dev));

                atomic_set(&eeh_fail_count, 0);
                notifier_call_chain (&eeh_notifier_chain,
                                     EEH_NOTIFY_FREEZE, event);

                pci_dev_put(event->dev);
                kfree(event);
        }
}

/**
 * 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));
}

/**
 * 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;
        int rc, reset_state;
        struct eeh_event  *event;
        struct pci_dn *pdn;

        __get_cpu_var(total_mmio_ffs)++;

        if (!eeh_subsystem_enabled)
                return 0;

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

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

        if (!pdn->eeh_config_addr) {
                __get_cpu_var(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...
         */
        if (pdn->eeh_mode & EEH_MODE_ISOLATED) {
                atomic_inc(&eeh_fail_count);
                if (atomic_read(&eeh_fail_count) >= EEH_MAX_FAILS) {
                        /* re-read the slot reset state */
                        if (read_slot_reset_state(pdn, rets) != 0)
                                rets[0] = -1;   /* reset state unknown */
                        eeh_panic(dev, rets[0]);
                }
                return 0;
        }

        /*
         * 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 (!(ret == 0 && rets[1] == 1 && (rets[0] == 2 || rets[0] == 4))) {
                __get_cpu_var(false_positives)++;
                return 0;
        }

        /* prevent repeated reports of this failure */
        pdn->eeh_mode |= EEH_MODE_ISOLATED;
         __get_cpu_var(slot_resets)++;

        reset_state = rets[0];

        spin_lock_irqsave(&slot_errbuf_lock, flags);
        memset(slot_errbuf, 0, eeh_error_buf_size);

        rc = rtas_call(ibm_slot_error_detail,
                       8, 1, NULL, pdn->eeh_config_addr,
                       BUID_HI(pdn->phb->buid),
                       BUID_LO(pdn->phb->buid), NULL, 0,
                       virt_to_phys(slot_errbuf),
                       eeh_error_buf_size,
                       1 /* Temporary Error */);

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

        printk(KERN_INFO "EEH: MMIO failure (%d) on device: %s %s\n",
               rets[0], dn->name, dn->full_name);
        event = kmalloc(sizeof(*event), GFP_ATOMIC);
        if (event == NULL) {
                eeh_panic(dev, reset_state);
                return 1;
        }

        event->dev = dev;
        event->dn = dn;
        event->reset_state = reset_state;

        /* We may or may not be called in an interrupt context */
        spin_lock_irqsave(&eeh_eventlist_lock, flags);
        list_add(&event->list, &eeh_eventlist);
        spin_unlock_irqrestore(&eeh_eventlist_lock, flags);

        /* 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. */
        dump_stack();
        schedule_work(&eeh_event_wq);

        return 0;
}

EXPORT_SYMBOL(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) {
                __get_cpu_var(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);

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)
{
        struct eeh_early_enable_info *info = data;
        int ret;
        char *status = get_property(dn, "status", NULL);
        u32 *class_code = (u32 *)get_property(dn, "class-code", NULL);
        u32 *vendor_id = (u32 *)get_property(dn, "vendor-id", NULL);
        u32 *device_id = (u32 *)get_property(dn, "device-id", NULL);
        u32 *regs;
        int enable;
        struct pci_dn *pdn = PCI_DN(dn);

        pdn->eeh_mode = 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;
        }

        /*
         * 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 ((*class_code >> 16) == PCI_BASE_CLASS_DISPLAY)
                enable = 0;

        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 = (u32 *)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);
                if (ret == 0) {
                        eeh_subsystem_enabled = 1;
                        pdn->eeh_mode |= EEH_MODE_SUPPORTED;
                        pdn->eeh_config_addr = regs[0];
#ifdef DEBUG
                        printk(KERN_DEBUG "EEH: %s: eeh enabled\n", dn->full_name);
#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);
        }

        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;

        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");

        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.
 */
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;
        if (NULL == phb || 0 == phb->buid) {
                printk(KERN_WARNING "EEH: Expected buid but found none for %s\n",
                       dn->full_name);
                dump_stack();
                return;
        }

        info.buid_hi = BUID_HI(phb->buid);
        info.buid_lo = BUID_LO(phb->buid);
        early_enable_eeh(dn, &info);
}
EXPORT_SYMBOL_GPL(eeh_add_device_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).
 */
void eeh_add_device_late(struct pci_dev *dev)
{
        struct device_node *dn;

        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);
        PCI_DN(dn)->pcidev = dev;

        pci_addr_cache_insert_device (dev);
}
EXPORT_SYMBOL_GPL(eeh_add_device_late);

/**
 * eeh_remove_device - undo EEH setup for the indicated pci device
 * @dev: pci device to be removed
 *
 * This routine should be when a device is removed from a running
 * system (e.g. by hotplug or dlpar).
 */
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);
        PCI_DN(dn)->pcidev = NULL;
        pci_dev_put (dev);
}
EXPORT_SYMBOL_GPL(eeh_remove_device);

static int proc_eeh_show(struct seq_file *m, void *v)
{
        unsigned int cpu;
        unsigned long ffs = 0, positives = 0, failures = 0;
        unsigned long resets = 0;
        unsigned long no_dev = 0, no_dn = 0, no_cfg = 0, no_check = 0;

        for_each_cpu(cpu) {
                ffs += per_cpu(total_mmio_ffs, cpu);
                positives += per_cpu(false_positives, cpu);
                failures += per_cpu(ignored_failures, cpu);
                resets += per_cpu(slot_resets, cpu);
                no_dev += per_cpu(no_device, cpu);
                no_dn += per_cpu(no_dn, cpu);
                no_cfg += per_cpu(no_cfg_addr, cpu);
                no_check += per_cpu(ignored_check, cpu);
        }

        if (0 == eeh_subsystem_enabled) {
                seq_printf(m, "EEH Subsystem is globally disabled\n");
                seq_printf(m, "eeh_total_mmio_ffs=%ld\n", 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_dev, no_dn, no_cfg, no_check,
                                ffs, positives, failures, resets);
        }

        return 0;
}

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

static 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 (systemcfg->platform & PLATFORM_PSERIES) {
                e = create_proc_entry("ppc64/eeh", 0, NULL);
                if (e)
                        e->proc_fops = &proc_eeh_operations;
        }

        return 0;
}
__initcall(eeh_init_proc);