x86/mm/pat: Don't report PAT on CPUs that don't support it

[linux/fpc-iii.git] / drivers / pci / pcie / aer / aerdrv_core.c

/*
 * drivers/pci/pcie/aer/aerdrv_core.c
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * This file implements the core part of PCI-Express AER. When an pci-express
 * error is delivered, an error message will be collected and printed to
 * console, then, an error recovery procedure will be executed by following
 * the pci error recovery rules.
 *
 * Copyright (C) 2006 Intel Corp.
 *      Tom Long Nguyen (tom.l.nguyen@intel.com)
 *      Zhang Yanmin (yanmin.zhang@intel.com)
 *
 */

#include <linux/module.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/pm.h>
#include <linux/suspend.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/kfifo.h>
#include "aerdrv.h"

#define PCI_EXP_AER_FLAGS       (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
                                 PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)

int pci_enable_pcie_error_reporting(struct pci_dev *dev)
{
        if (pcie_aer_get_firmware_first(dev))
                return -EIO;

        if (!dev->aer_cap)
                return -EIO;

        return pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_AER_FLAGS);
}
EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);

int pci_disable_pcie_error_reporting(struct pci_dev *dev)
{
        if (pcie_aer_get_firmware_first(dev))
                return -EIO;

        return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
                                          PCI_EXP_AER_FLAGS);
}
EXPORT_SYMBOL_GPL(pci_disable_pcie_error_reporting);

int pci_cleanup_aer_uncorrect_error_status(struct pci_dev *dev)
{
        int pos;
        u32 status;

        pos = dev->aer_cap;
        if (!pos)
                return -EIO;

        pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, &status);
        if (status)
                pci_write_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, status);

        return 0;
}
EXPORT_SYMBOL_GPL(pci_cleanup_aer_uncorrect_error_status);

int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
{
        int pos;
        u32 status;
        int port_type;

        if (!pci_is_pcie(dev))
                return -ENODEV;

        pos = dev->aer_cap;
        if (!pos)
                return -EIO;

        port_type = pci_pcie_type(dev);
        if (port_type == PCI_EXP_TYPE_ROOT_PORT) {
                pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &status);
                pci_write_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, status);
        }

        pci_read_config_dword(dev, pos + PCI_ERR_COR_STATUS, &status);
        pci_write_config_dword(dev, pos + PCI_ERR_COR_STATUS, status);

        pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, &status);
        pci_write_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, status);

        return 0;
}

int pci_aer_init(struct pci_dev *dev)
{
        dev->aer_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
        return pci_cleanup_aer_error_status_regs(dev);
}

/**
 * add_error_device - list device to be handled
 * @e_info: pointer to error info
 * @dev: pointer to pci_dev to be added
 */
static int add_error_device(struct aer_err_info *e_info, struct pci_dev *dev)
{
        if (e_info->error_dev_num < AER_MAX_MULTI_ERR_DEVICES) {
                e_info->dev[e_info->error_dev_num] = dev;
                e_info->error_dev_num++;
                return 0;
        }
        return -ENOSPC;
}

/**
 * is_error_source - check whether the device is source of reported error
 * @dev: pointer to pci_dev to be checked
 * @e_info: pointer to reported error info
 */
static bool is_error_source(struct pci_dev *dev, struct aer_err_info *e_info)
{
        int pos;
        u32 status, mask;
        u16 reg16;

        /*
         * When bus id is equal to 0, it might be a bad id
         * reported by root port.
         */
        if ((PCI_BUS_NUM(e_info->id) != 0) &&
            !(dev->bus->bus_flags & PCI_BUS_FLAGS_NO_AERSID)) {
                /* Device ID match? */
                if (e_info->id == ((dev->bus->number << 8) | dev->devfn))
                        return true;

                /* Continue id comparing if there is no multiple error */
                if (!e_info->multi_error_valid)
                        return false;
        }

        /*
         * When either
         *      1) bus id is equal to 0. Some ports might lose the bus
         *              id of error source id;
         *      2) bus flag PCI_BUS_FLAGS_NO_AERSID is set
         *      3) There are multiple errors and prior ID comparing fails;
         * We check AER status registers to find possible reporter.
         */
        if (atomic_read(&dev->enable_cnt) == 0)
                return false;

        /* Check if AER is enabled */
        pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &reg16);
        if (!(reg16 & PCI_EXP_AER_FLAGS))
                return false;

        pos = dev->aer_cap;
        if (!pos)
                return false;

        /* Check if error is recorded */
        if (e_info->severity == AER_CORRECTABLE) {
                pci_read_config_dword(dev, pos + PCI_ERR_COR_STATUS, &status);
                pci_read_config_dword(dev, pos + PCI_ERR_COR_MASK, &mask);
        } else {
                pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, &status);
                pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_MASK, &mask);
        }
        if (status & ~mask)
                return true;

        return false;
}

static int find_device_iter(struct pci_dev *dev, void *data)
{
        struct aer_err_info *e_info = (struct aer_err_info *)data;

        if (is_error_source(dev, e_info)) {
                /* List this device */
                if (add_error_device(e_info, dev)) {
                        /* We cannot handle more... Stop iteration */
                        /* TODO: Should print error message here? */
                        return 1;
                }

                /* If there is only a single error, stop iteration */
                if (!e_info->multi_error_valid)
                        return 1;
        }
        return 0;
}

/**
 * find_source_device - search through device hierarchy for source device
 * @parent: pointer to Root Port pci_dev data structure
 * @e_info: including detailed error information such like id
 *
 * Return true if found.
 *
 * Invoked by DPC when error is detected at the Root Port.
 * Caller of this function must set id, severity, and multi_error_valid of
 * struct aer_err_info pointed by @e_info properly.  This function must fill
 * e_info->error_dev_num and e_info->dev[], based on the given information.
 */
static bool find_source_device(struct pci_dev *parent,
                struct aer_err_info *e_info)
{
        struct pci_dev *dev = parent;
        int result;

        /* Must reset in this function */
        e_info->error_dev_num = 0;

        /* Is Root Port an agent that sends error message? */
        result = find_device_iter(dev, e_info);
        if (result)
                return true;

        pci_walk_bus(parent->subordinate, find_device_iter, e_info);

        if (!e_info->error_dev_num) {
                dev_printk(KERN_DEBUG, &parent->dev,
                                "can't find device of ID%04x\n",
                                e_info->id);
                return false;
        }
        return true;
}

static int report_error_detected(struct pci_dev *dev, void *data)
{
        pci_ers_result_t vote;
        const struct pci_error_handlers *err_handler;
        struct aer_broadcast_data *result_data;
        result_data = (struct aer_broadcast_data *) data;

        device_lock(&dev->dev);
        dev->error_state = result_data->state;

        if (!dev->driver ||
                !dev->driver->err_handler ||
                !dev->driver->err_handler->error_detected) {
                if (result_data->state == pci_channel_io_frozen &&
                        dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
                        /*
                         * In case of fatal recovery, if one of down-
                         * stream device has no driver. We might be
                         * unable to recover because a later insmod
                         * of a driver for this device is unaware of
                         * its hw state.
                         */
                        dev_printk(KERN_DEBUG, &dev->dev, "device has %s\n",
                                   dev->driver ?
                                   "no AER-aware driver" : "no driver");
                }

                /*
                 * If there's any device in the subtree that does not
                 * have an error_detected callback, returning
                 * PCI_ERS_RESULT_NO_AER_DRIVER prevents calling of
                 * the subsequent mmio_enabled/slot_reset/resume
                 * callbacks of "any" device in the subtree. All the
                 * devices in the subtree are left in the error state
                 * without recovery.
                 */

                if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE)
                        vote = PCI_ERS_RESULT_NO_AER_DRIVER;
                else
                        vote = PCI_ERS_RESULT_NONE;
        } else {
                err_handler = dev->driver->err_handler;
                vote = err_handler->error_detected(dev, result_data->state);
        }

        result_data->result = merge_result(result_data->result, vote);
        device_unlock(&dev->dev);
        return 0;
}

static int report_mmio_enabled(struct pci_dev *dev, void *data)
{
        pci_ers_result_t vote;
        const struct pci_error_handlers *err_handler;
        struct aer_broadcast_data *result_data;
        result_data = (struct aer_broadcast_data *) data;

        device_lock(&dev->dev);
        if (!dev->driver ||
                !dev->driver->err_handler ||
                !dev->driver->err_handler->mmio_enabled)
                goto out;

        err_handler = dev->driver->err_handler;
        vote = err_handler->mmio_enabled(dev);
        result_data->result = merge_result(result_data->result, vote);
out:
        device_unlock(&dev->dev);
        return 0;
}

static int report_slot_reset(struct pci_dev *dev, void *data)
{
        pci_ers_result_t vote;
        const struct pci_error_handlers *err_handler;
        struct aer_broadcast_data *result_data;
        result_data = (struct aer_broadcast_data *) data;

        device_lock(&dev->dev);
        if (!dev->driver ||
                !dev->driver->err_handler ||
                !dev->driver->err_handler->slot_reset)
                goto out;

        err_handler = dev->driver->err_handler;
        vote = err_handler->slot_reset(dev);
        result_data->result = merge_result(result_data->result, vote);
out:
        device_unlock(&dev->dev);
        return 0;
}

static int report_resume(struct pci_dev *dev, void *data)
{
        const struct pci_error_handlers *err_handler;

        device_lock(&dev->dev);
        dev->error_state = pci_channel_io_normal;

        if (!dev->driver ||
                !dev->driver->err_handler ||
                !dev->driver->err_handler->resume)
                goto out;

        err_handler = dev->driver->err_handler;
        err_handler->resume(dev);
out:
        device_unlock(&dev->dev);
        return 0;
}

/**
 * broadcast_error_message - handle message broadcast to downstream drivers
 * @dev: pointer to from where in a hierarchy message is broadcasted down
 * @state: error state
 * @error_mesg: message to print
 * @cb: callback to be broadcasted
 *
 * Invoked during error recovery process. Once being invoked, the content
 * of error severity will be broadcasted to all downstream drivers in a
 * hierarchy in question.
 */
static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
        enum pci_channel_state state,
        char *error_mesg,
        int (*cb)(struct pci_dev *, void *))
{
        struct aer_broadcast_data result_data;

        dev_printk(KERN_DEBUG, &dev->dev, "broadcast %s message\n", error_mesg);
        result_data.state = state;
        if (cb == report_error_detected)
                result_data.result = PCI_ERS_RESULT_CAN_RECOVER;
        else
                result_data.result = PCI_ERS_RESULT_RECOVERED;

        if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                /*
                 * If the error is reported by a bridge, we think this error
                 * is related to the downstream link of the bridge, so we
                 * do error recovery on all subordinates of the bridge instead
                 * of the bridge and clear the error status of the bridge.
                 */
                if (cb == report_error_detected)
                        dev->error_state = state;
                pci_walk_bus(dev->subordinate, cb, &result_data);
                if (cb == report_resume) {
                        pci_cleanup_aer_uncorrect_error_status(dev);
                        dev->error_state = pci_channel_io_normal;
                }
        } else {
                /*
                 * If the error is reported by an end point, we think this
                 * error is related to the upstream link of the end point.
                 */
                pci_walk_bus(dev->bus, cb, &result_data);
        }

        return result_data.result;
}

/**
 * default_reset_link - default reset function
 * @dev: pointer to pci_dev data structure
 *
 * Invoked when performing link reset on a Downstream Port or a
 * Root Port with no aer driver.
 */
static pci_ers_result_t default_reset_link(struct pci_dev *dev)
{
        pci_reset_bridge_secondary_bus(dev);
        dev_printk(KERN_DEBUG, &dev->dev, "downstream link has been reset\n");
        return PCI_ERS_RESULT_RECOVERED;
}

static int find_aer_service_iter(struct device *device, void *data)
{
        struct pcie_port_service_driver *service_driver, **drv;

        drv = (struct pcie_port_service_driver **) data;

        if (device->bus == &pcie_port_bus_type && device->driver) {
                service_driver = to_service_driver(device->driver);
                if (service_driver->service == PCIE_PORT_SERVICE_AER) {
                        *drv = service_driver;
                        return 1;
                }
        }

        return 0;
}

static struct pcie_port_service_driver *find_aer_service(struct pci_dev *dev)
{
        struct pcie_port_service_driver *drv = NULL;

        device_for_each_child(&dev->dev, &drv, find_aer_service_iter);

        return drv;
}

static pci_ers_result_t reset_link(struct pci_dev *dev)
{
        struct pci_dev *udev;
        pci_ers_result_t status;
        struct pcie_port_service_driver *driver;

        if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                /* Reset this port for all subordinates */
                udev = dev;
        } else {
                /* Reset the upstream component (likely downstream port) */
                udev = dev->bus->self;
        }

        /* Use the aer driver of the component firstly */
        driver = find_aer_service(udev);

        if (driver && driver->reset_link) {
                status = driver->reset_link(udev);
        } else if (udev->has_secondary_link) {
                status = default_reset_link(udev);
        } else {
                dev_printk(KERN_DEBUG, &dev->dev,
                        "no link-reset support at upstream device %s\n",
                        pci_name(udev));
                return PCI_ERS_RESULT_DISCONNECT;
        }

        if (status != PCI_ERS_RESULT_RECOVERED) {
                dev_printk(KERN_DEBUG, &dev->dev,
                        "link reset at upstream device %s failed\n",
                        pci_name(udev));
                return PCI_ERS_RESULT_DISCONNECT;
        }

        return status;
}

/**
 * do_recovery - handle nonfatal/fatal error recovery process
 * @dev: pointer to a pci_dev data structure of agent detecting an error
 * @severity: error severity type
 *
 * Invoked when an error is nonfatal/fatal. Once being invoked, broadcast
 * error detected message to all downstream drivers within a hierarchy in
 * question and return the returned code.
 */
static void do_recovery(struct pci_dev *dev, int severity)
{
        pci_ers_result_t status, result = PCI_ERS_RESULT_RECOVERED;
        enum pci_channel_state state;

        if (severity == AER_FATAL)
                state = pci_channel_io_frozen;
        else
                state = pci_channel_io_normal;

        status = broadcast_error_message(dev,
                        state,
                        "error_detected",
                        report_error_detected);

        if (severity == AER_FATAL) {
                result = reset_link(dev);
                if (result != PCI_ERS_RESULT_RECOVERED)
                        goto failed;
        }

        if (status == PCI_ERS_RESULT_CAN_RECOVER)
                status = broadcast_error_message(dev,
                                state,
                                "mmio_enabled",
                                report_mmio_enabled);

        if (status == PCI_ERS_RESULT_NEED_RESET) {
                /*
                 * TODO: Should call platform-specific
                 * functions to reset slot before calling
                 * drivers' slot_reset callbacks?
                 */
                status = broadcast_error_message(dev,
                                state,
                                "slot_reset",
                                report_slot_reset);
        }

        if (status != PCI_ERS_RESULT_RECOVERED)
                goto failed;

        broadcast_error_message(dev,
                                state,
                                "resume",
                                report_resume);

        dev_info(&dev->dev, "AER: Device recovery successful\n");
        return;

failed:
        /* TODO: Should kernel panic here? */
        dev_info(&dev->dev, "AER: Device recovery failed\n");
}

/**
 * handle_error_source - handle logging error into an event log
 * @aerdev: pointer to pcie_device data structure of the root port
 * @dev: pointer to pci_dev data structure of error source device
 * @info: comprehensive error information
 *
 * Invoked when an error being detected by Root Port.
 */
static void handle_error_source(struct pcie_device *aerdev,
        struct pci_dev *dev,
        struct aer_err_info *info)
{
        int pos;

        if (info->severity == AER_CORRECTABLE) {
                /*
                 * Correctable error does not need software intervention.
                 * No need to go through error recovery process.
                 */
                pos = dev->aer_cap;
                if (pos)
                        pci_write_config_dword(dev, pos + PCI_ERR_COR_STATUS,
                                        info->status);
        } else
                do_recovery(dev, info->severity);
}

#ifdef CONFIG_ACPI_APEI_PCIEAER
static void aer_recover_work_func(struct work_struct *work);

#define AER_RECOVER_RING_ORDER          4
#define AER_RECOVER_RING_SIZE           (1 << AER_RECOVER_RING_ORDER)

struct aer_recover_entry {
        u8      bus;
        u8      devfn;
        u16     domain;
        int     severity;
        struct aer_capability_regs *regs;
};

static DEFINE_KFIFO(aer_recover_ring, struct aer_recover_entry,
                    AER_RECOVER_RING_SIZE);
/*
 * Mutual exclusion for writers of aer_recover_ring, reader side don't
 * need lock, because there is only one reader and lock is not needed
 * between reader and writer.
 */
static DEFINE_SPINLOCK(aer_recover_ring_lock);
static DECLARE_WORK(aer_recover_work, aer_recover_work_func);

void aer_recover_queue(int domain, unsigned int bus, unsigned int devfn,
                       int severity, struct aer_capability_regs *aer_regs)
{
        unsigned long flags;
        struct aer_recover_entry entry = {
                .bus            = bus,
                .devfn          = devfn,
                .domain         = domain,
                .severity       = severity,
                .regs           = aer_regs,
        };

        spin_lock_irqsave(&aer_recover_ring_lock, flags);
        if (kfifo_put(&aer_recover_ring, entry))
                schedule_work(&aer_recover_work);
        else
                pr_err("AER recover: Buffer overflow when recovering AER for %04x:%02x:%02x:%x\n",
                       domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
        spin_unlock_irqrestore(&aer_recover_ring_lock, flags);
}
EXPORT_SYMBOL_GPL(aer_recover_queue);

static void aer_recover_work_func(struct work_struct *work)
{
        struct aer_recover_entry entry;
        struct pci_dev *pdev;

        while (kfifo_get(&aer_recover_ring, &entry)) {
                pdev = pci_get_domain_bus_and_slot(entry.domain, entry.bus,
                                                   entry.devfn);
                if (!pdev) {
                        pr_err("AER recover: Can not find pci_dev for %04x:%02x:%02x:%x\n",
                               entry.domain, entry.bus,
                               PCI_SLOT(entry.devfn), PCI_FUNC(entry.devfn));
                        continue;
                }
                cper_print_aer(pdev, entry.severity, entry.regs);
                do_recovery(pdev, entry.severity);
                pci_dev_put(pdev);
        }
}
#endif

/**
 * get_device_error_info - read error status from dev and store it to info
 * @dev: pointer to the device expected to have a error record
 * @info: pointer to structure to store the error record
 *
 * Return 1 on success, 0 on error.
 *
 * Note that @info is reused among all error devices. Clear fields properly.
 */
static int get_device_error_info(struct pci_dev *dev, struct aer_err_info *info)
{
        int pos, temp;

        /* Must reset in this function */
        info->status = 0;
        info->tlp_header_valid = 0;

        pos = dev->aer_cap;

        /* The device might not support AER */
        if (!pos)
                return 1;

        if (info->severity == AER_CORRECTABLE) {
                pci_read_config_dword(dev, pos + PCI_ERR_COR_STATUS,
                        &info->status);
                pci_read_config_dword(dev, pos + PCI_ERR_COR_MASK,
                        &info->mask);
                if (!(info->status & ~info->mask))
                        return 0;
        } else if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
                info->severity == AER_NONFATAL) {

                /* Link is still healthy for IO reads */
                pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS,
                        &info->status);
                pci_read_config_dword(dev, pos + PCI_ERR_UNCOR_MASK,
                        &info->mask);
                if (!(info->status & ~info->mask))
                        return 0;

                /* Get First Error Pointer */
                pci_read_config_dword(dev, pos + PCI_ERR_CAP, &temp);
                info->first_error = PCI_ERR_CAP_FEP(temp);

                if (info->status & AER_LOG_TLP_MASKS) {
                        info->tlp_header_valid = 1;
                        pci_read_config_dword(dev,
                                pos + PCI_ERR_HEADER_LOG, &info->tlp.dw0);
                        pci_read_config_dword(dev,
                                pos + PCI_ERR_HEADER_LOG + 4, &info->tlp.dw1);
                        pci_read_config_dword(dev,
                                pos + PCI_ERR_HEADER_LOG + 8, &info->tlp.dw2);
                        pci_read_config_dword(dev,
                                pos + PCI_ERR_HEADER_LOG + 12, &info->tlp.dw3);
                }
        }

        return 1;
}

static inline void aer_process_err_devices(struct pcie_device *p_device,
                        struct aer_err_info *e_info)
{
        int i;

        /* Report all before handle them, not to lost records by reset etc. */
        for (i = 0; i < e_info->error_dev_num && e_info->dev[i]; i++) {
                if (get_device_error_info(e_info->dev[i], e_info))
                        aer_print_error(e_info->dev[i], e_info);
        }
        for (i = 0; i < e_info->error_dev_num && e_info->dev[i]; i++) {
                if (get_device_error_info(e_info->dev[i], e_info))
                        handle_error_source(p_device, e_info->dev[i], e_info);
        }
}

/**
 * aer_isr_one_error - consume an error detected by root port
 * @p_device: pointer to error root port service device
 * @e_src: pointer to an error source
 */
static void aer_isr_one_error(struct pcie_device *p_device,
                struct aer_err_source *e_src)
{
        struct aer_rpc *rpc = get_service_data(p_device);
        struct aer_err_info *e_info = &rpc->e_info;

        /*
         * There is a possibility that both correctable error and
         * uncorrectable error being logged. Report correctable error first.
         */
        if (e_src->status & PCI_ERR_ROOT_COR_RCV) {
                e_info->id = ERR_COR_ID(e_src->id);
                e_info->severity = AER_CORRECTABLE;

                if (e_src->status & PCI_ERR_ROOT_MULTI_COR_RCV)
                        e_info->multi_error_valid = 1;
                else
                        e_info->multi_error_valid = 0;

                aer_print_port_info(p_device->port, e_info);

                if (find_source_device(p_device->port, e_info))
                        aer_process_err_devices(p_device, e_info);
        }

        if (e_src->status & PCI_ERR_ROOT_UNCOR_RCV) {
                e_info->id = ERR_UNCOR_ID(e_src->id);

                if (e_src->status & PCI_ERR_ROOT_FATAL_RCV)
                        e_info->severity = AER_FATAL;
                else
                        e_info->severity = AER_NONFATAL;

                if (e_src->status & PCI_ERR_ROOT_MULTI_UNCOR_RCV)
                        e_info->multi_error_valid = 1;
                else
                        e_info->multi_error_valid = 0;

                aer_print_port_info(p_device->port, e_info);

                if (find_source_device(p_device->port, e_info))
                        aer_process_err_devices(p_device, e_info);
        }
}

/**
 * get_e_source - retrieve an error source
 * @rpc: pointer to the root port which holds an error
 * @e_src: pointer to store retrieved error source
 *
 * Return 1 if an error source is retrieved, otherwise 0.
 *
 * Invoked by DPC handler to consume an error.
 */
static int get_e_source(struct aer_rpc *rpc, struct aer_err_source *e_src)
{
        unsigned long flags;

        /* Lock access to Root error producer/consumer index */
        spin_lock_irqsave(&rpc->e_lock, flags);
        if (rpc->prod_idx == rpc->cons_idx) {
                spin_unlock_irqrestore(&rpc->e_lock, flags);
                return 0;
        }

        *e_src = rpc->e_sources[rpc->cons_idx];
        rpc->cons_idx++;
        if (rpc->cons_idx == AER_ERROR_SOURCES_MAX)
                rpc->cons_idx = 0;
        spin_unlock_irqrestore(&rpc->e_lock, flags);

        return 1;
}

/**
 * aer_isr - consume errors detected by root port
 * @work: definition of this work item
 *
 * Invoked, as DPC, when root port records new detected error
 */
void aer_isr(struct work_struct *work)
{
        struct aer_rpc *rpc = container_of(work, struct aer_rpc, dpc_handler);
        struct pcie_device *p_device = rpc->rpd;
        struct aer_err_source uninitialized_var(e_src);

        mutex_lock(&rpc->rpc_mutex);
        while (get_e_source(rpc, &e_src))
                aer_isr_one_error(p_device, &e_src);
        mutex_unlock(&rpc->rpc_mutex);
}