/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2019 Intel Corporation
 */

#include "i915_drv.h"

#include "intel_context.h"
#include "intel_engine.h"
#include "intel_engine_heartbeat.h"
#include "intel_engine_pm.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
#include "intel_rc6.h"
#include "intel_ring.h"
#include "shmem_utils.h"

static int __engine_unpark(struct intel_wakeref *wf)
{
        struct intel_engine_cs *engine =
                container_of(wf, typeof(*engine), wakeref);
        struct intel_context *ce;

        ENGINE_TRACE(engine, "\n");

        intel_gt_pm_get(engine->gt);

        /* Discard stale context state from across idling */
        ce = engine->kernel_context;
        if (ce) {
                GEM_BUG_ON(test_bit(CONTEXT_VALID_BIT, &ce->flags));

                /* First poison the image to verify we never fully trust it */
                if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && ce->state) {
                        struct drm_i915_gem_object *obj = ce->state->obj;
                        int type = i915_coherent_map_type(engine->i915);
                        void *map;

                        map = i915_gem_object_pin_map(obj, type);
                        if (!IS_ERR(map)) {
                                memset(map, CONTEXT_REDZONE, obj->base.size);
                                i915_gem_object_flush_map(obj);
                                i915_gem_object_unpin_map(obj);
                        }
                }

                ce->ops->reset(ce);
        }

        if (engine->unpark)
                engine->unpark(engine);

        intel_engine_unpark_heartbeat(engine);
        return 0;
}

#if IS_ENABLED(CONFIG_LOCKDEP)

static inline unsigned long __timeline_mark_lock(struct intel_context *ce)
{
        unsigned long flags;

        local_irq_save(flags);
        mutex_acquire(&ce->timeline->mutex.dep_map, 2, 0, _THIS_IP_);

        return flags;
}

static inline void __timeline_mark_unlock(struct intel_context *ce,
                                          unsigned long flags)
{
        mutex_release(&ce->timeline->mutex.dep_map, _THIS_IP_);
        local_irq_restore(flags);
}

#else

static inline unsigned long __timeline_mark_lock(struct intel_context *ce)
{
        return 0;
}

static inline void __timeline_mark_unlock(struct intel_context *ce,
                                          unsigned long flags)
{
}

#endif /* !IS_ENABLED(CONFIG_LOCKDEP) */

static void duration(struct dma_fence *fence, struct dma_fence_cb *cb)
{
        struct i915_request *rq = to_request(fence);

        ewma__engine_latency_add(&rq->engine->latency,
                                 ktime_us_delta(rq->fence.timestamp,
                                                rq->duration.emitted));
}

static void
__queue_and_release_pm(struct i915_request *rq,
                       struct intel_timeline *tl,
                       struct intel_engine_cs *engine)
{
        struct intel_gt_timelines *timelines = &engine->gt->timelines;

        ENGINE_TRACE(engine, "parking\n");

        /*
         * We have to serialise all potential retirement paths with our
         * submission, as we don't want to underflow either the
         * engine->wakeref.counter or our timeline->active_count.
         *
         * Equally, we cannot allow a new submission to start until
         * after we finish queueing, nor could we allow that submitter
         * to retire us before we are ready!
         */
        spin_lock(&timelines->lock);

        /* Let intel_gt_retire_requests() retire us (acquired under lock) */
        if (!atomic_fetch_inc(&tl->active_count))
                list_add_tail(&tl->link, &timelines->active_list);

        /* Hand the request over to HW and so engine_retire() */
        __i915_request_queue(rq, NULL);

        /* Let new submissions commence (and maybe retire this timeline) */
        __intel_wakeref_defer_park(&engine->wakeref);

        spin_unlock(&timelines->lock);
}

static bool switch_to_kernel_context(struct intel_engine_cs *engine)
{
        struct intel_context *ce = engine->kernel_context;
        struct i915_request *rq;
        unsigned long flags;
        bool result = true;

        /* GPU is pointing to the void, as good as in the kernel context. */
        if (intel_gt_is_wedged(engine->gt))
                return true;

        GEM_BUG_ON(!intel_context_is_barrier(ce));

        /* Already inside the kernel context, safe to power down. */
        if (engine->wakeref_serial == engine->serial)
                return true;

        /*
         * Note, we do this without taking the timeline->mutex. We cannot
         * as we may be called while retiring the kernel context and so
         * already underneath the timeline->mutex. Instead we rely on the
         * exclusive property of the __engine_park that prevents anyone
         * else from creating a request on this engine. This also requires
         * that the ring is empty and we avoid any waits while constructing
         * the context, as they assume protection by the timeline->mutex.
         * This should hold true as we can only park the engine after
         * retiring the last request, thus all rings should be empty and
         * all timelines idle.
         *
         * For unlocking, there are 2 other parties and the GPU who have a
         * stake here.
         *
         * A new gpu user will be waiting on the engine-pm to start their
         * engine_unpark. New waiters are predicated on engine->wakeref.count
         * and so intel_wakeref_defer_park() acts like a mutex_unlock of the
         * engine->wakeref.
         *
         * The other party is intel_gt_retire_requests(), which is walking the
         * list of active timelines looking for completions. Meanwhile as soon
         * as we call __i915_request_queue(), the GPU may complete our request.
         * Ergo, if we put ourselves on the timelines.active_list
         * (se intel_timeline_enter()) before we increment the
         * engine->wakeref.count, we may see the request completion and retire
         * it causing an underflow of the engine->wakeref.
         */
        flags = __timeline_mark_lock(ce);
        GEM_BUG_ON(atomic_read(&ce->timeline->active_count) < 0);

        rq = __i915_request_create(ce, GFP_NOWAIT);
        if (IS_ERR(rq))
                /* Context switch failed, hope for the best! Maybe reset? */
                goto out_unlock;

        /* Check again on the next retirement. */
        engine->wakeref_serial = engine->serial + 1;
        i915_request_add_active_barriers(rq);

        /* Install ourselves as a preemption barrier */
        rq->sched.attr.priority = I915_PRIORITY_BARRIER;
        if (likely(!__i915_request_commit(rq))) { /* engine should be idle! */
                /*
                 * Use an interrupt for precise measurement of duration,
                 * otherwise we rely on someone else retiring all the requests
                 * which may delay the signaling (i.e. we will likely wait
                 * until the background request retirement running every
                 * second or two).
                 */
                BUILD_BUG_ON(sizeof(rq->duration) > sizeof(rq->submitq));
                dma_fence_add_callback(&rq->fence, &rq->duration.cb, duration);
                rq->duration.emitted = ktime_get();
        }

        /* Expose ourselves to the world */
        __queue_and_release_pm(rq, ce->timeline, engine);

        result = false;
out_unlock:
        __timeline_mark_unlock(ce, flags);
        return result;
}

static void call_idle_barriers(struct intel_engine_cs *engine)
{
        struct llist_node *node, *next;

        llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks)) {
                struct dma_fence_cb *cb =
                        container_of((struct list_head *)node,
                                     typeof(*cb), node);

                cb->func(ERR_PTR(-EAGAIN), cb);
        }
}

static int __engine_park(struct intel_wakeref *wf)
{
        struct intel_engine_cs *engine =
                container_of(wf, typeof(*engine), wakeref);

        engine->saturated = 0;

        /*
         * If one and only one request is completed between pm events,
         * we know that we are inside the kernel context and it is
         * safe to power down. (We are paranoid in case that runtime
         * suspend causes corruption to the active context image, and
         * want to avoid that impacting userspace.)
         */
        if (!switch_to_kernel_context(engine))
                return -EBUSY;

        ENGINE_TRACE(engine, "parked\n");

        call_idle_barriers(engine); /* cleanup after wedging */

        intel_engine_park_heartbeat(engine);
        intel_engine_disarm_breadcrumbs(engine);

        /* Must be reset upon idling, or we may miss the busy wakeup. */
        GEM_BUG_ON(engine->execlists.queue_priority_hint != INT_MIN);

        if (engine->park)
                engine->park(engine);

        engine->execlists.no_priolist = false;

        /* While gt calls i915_vma_parked(), we have to break the lock cycle */
        intel_gt_pm_put_async(engine->gt);
        return 0;
}

static const struct intel_wakeref_ops wf_ops = {
        .get = __engine_unpark,
        .put = __engine_park,
};

void intel_engine_init__pm(struct intel_engine_cs *engine)
{
        struct intel_runtime_pm *rpm = engine->uncore->rpm;

        intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
        intel_engine_init_heartbeat(engine);
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_engine_pm.c"
#endif