// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (c) 2005 Linas Vepstas <linas@linas.org>
 */

#include <linux/delay.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/semaphore.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <asm/eeh_event.h>
#include <asm/ppc-pci.h>

/** Overview:
 *  EEH error states may be detected within exception handlers;
 *  however, the recovery processing needs to occur asynchronously
 *  in a normal kernel context and not an interrupt context.
 *  This pair of routines creates an event and queues it onto a
 *  work-queue, where a worker thread can drive recovery.
 */

static DEFINE_SPINLOCK(eeh_eventlist_lock);
static DECLARE_COMPLETION(eeh_eventlist_event);
static LIST_HEAD(eeh_eventlist);

/**
 * eeh_event_handler - Dispatch EEH events.
 * @dummy - unused
 *
 * 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.
 */
static int eeh_event_handler(void * dummy)
{
        unsigned long flags;
        struct eeh_event *event;

        while (!kthread_should_stop()) {
                if (wait_for_completion_interruptible(&eeh_eventlist_event))
                        break;

                /* Fetch EEH event from the queue */
                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)
                        continue;

                /* We might have event without binding PE */
                if (event->pe)
                        eeh_handle_normal_event(event->pe);
                else
                        eeh_handle_special_event();

                kfree(event);
        }

        return 0;
}

/**
 * eeh_event_init - Start kernel thread to handle EEH events
 *
 * This routine is called to start the kernel thread for processing
 * EEH event.
 */
int eeh_event_init(void)
{
        struct task_struct *t;
        int ret = 0;

        t = kthread_run(eeh_event_handler, NULL, "eehd");
        if (IS_ERR(t)) {
                ret = PTR_ERR(t);
                pr_err("%s: Failed to start EEH daemon (%d)\n",
                        __func__, ret);
                return ret;
        }

        return 0;
}

/**
 * eeh_send_failure_event - Generate a PCI error event
 * @pe: EEH PE
 *
 * This routine can be called within an interrupt context;
 * the actual event will be delivered in a normal context
 * (from a workqueue).
 */
int __eeh_send_failure_event(struct eeh_pe *pe)
{
        unsigned long flags;
        struct eeh_event *event;

        event = kzalloc(sizeof(*event), GFP_ATOMIC);
        if (!event) {
                pr_err("EEH: out of memory, event not handled\n");
                return -ENOMEM;
        }
        event->pe = pe;

        /*
         * Mark the PE as recovering before inserting it in the queue.
         * This prevents the PE from being free()ed by a hotplug driver
         * while the PE is sitting in the event queue.
         */
        if (pe) {
#ifdef CONFIG_STACKTRACE
                /*
                 * Save the current stack trace so we can dump it from the
                 * event handler thread.
                 */
                pe->trace_entries = stack_trace_save(pe->stack_trace,
                                         ARRAY_SIZE(pe->stack_trace), 0);
#endif /* CONFIG_STACKTRACE */

                eeh_pe_state_mark(pe, EEH_PE_RECOVERING);
        }

        /* 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);

        /* For EEH deamon to knick in */
        complete(&eeh_eventlist_event);

        return 0;
}

int eeh_send_failure_event(struct eeh_pe *pe)
{
        /*
         * If we've manually supressed recovery events via debugfs
         * then just drop it on the floor.
         */
        if (eeh_debugfs_no_recover) {
                pr_err("EEH: Event dropped due to no_recover setting\n");
                return 0;
        }

        return __eeh_send_failure_event(pe);
}

/**
 * eeh_remove_event - Remove EEH event from the queue
 * @pe: Event binding to the PE
 * @force: Event will be removed unconditionally
 *
 * On PowerNV platform, we might have subsequent coming events
 * is part of the former one. For that case, those subsequent
 * coming events are totally duplicated and unnecessary, thus
 * they should be removed.
 */
void eeh_remove_event(struct eeh_pe *pe, bool force)
{
        unsigned long flags;
        struct eeh_event *event, *tmp;

        /*
         * If we have NULL PE passed in, we have dead IOC
         * or we're sure we can report all existing errors
         * by the caller.
         *
         * With "force", the event with associated PE that
         * have been isolated, the event won't be removed
         * to avoid event lost.
         */
        spin_lock_irqsave(&eeh_eventlist_lock, flags);
        list_for_each_entry_safe(event, tmp, &eeh_eventlist, list) {
                if (!force && event->pe &&
                    (event->pe->state & EEH_PE_ISOLATED))
                        continue;

                if (!pe) {
                        list_del(&event->list);
                        kfree(event);
                } else if (pe->type & EEH_PE_PHB) {
                        if (event->pe && event->pe->phb == pe->phb) {
                                list_del(&event->list);
                                kfree(event);
                        }
                } else if (event->pe == pe) {
                        list_del(&event->list);
                        kfree(event);
                }
        }
        spin_unlock_irqrestore(&eeh_eventlist_lock, flags);
}