/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2016 Intel Corporation
 */

#include <linux/dma-fence-array.h>
#include <linux/dma-fence-chain.h>
#include <linux/jiffies.h>

#include "gt/intel_engine.h"

#include "dma_resv_utils.h"
#include "i915_gem_ioctls.h"
#include "i915_gem_object.h"

static long
i915_gem_object_wait_fence(struct dma_fence *fence,
                           unsigned int flags,
                           long timeout)
{
        BUILD_BUG_ON(I915_WAIT_INTERRUPTIBLE != 0x1);

        if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                return timeout;

        if (dma_fence_is_i915(fence))
                return i915_request_wait(to_request(fence), flags, timeout);

        return dma_fence_wait_timeout(fence,
                                      flags & I915_WAIT_INTERRUPTIBLE,
                                      timeout);
}

static long
i915_gem_object_wait_reservation(struct dma_resv *resv,
                                 unsigned int flags,
                                 long timeout)
{
        struct dma_fence *excl;
        bool prune_fences = false;

        if (flags & I915_WAIT_ALL) {
                struct dma_fence **shared;
                unsigned int count, i;
                int ret;

                ret = dma_resv_get_fences(resv, &excl, &count, &shared);
                if (ret)
                        return ret;

                for (i = 0; i < count; i++) {
                        timeout = i915_gem_object_wait_fence(shared[i],
                                                             flags, timeout);
                        if (timeout < 0)
                                break;

                        dma_fence_put(shared[i]);
                }

                for (; i < count; i++)
                        dma_fence_put(shared[i]);
                kfree(shared);

                /*
                 * If both shared fences and an exclusive fence exist,
                 * then by construction the shared fences must be later
                 * than the exclusive fence. If we successfully wait for
                 * all the shared fences, we know that the exclusive fence
                 * must all be signaled. If all the shared fences are
                 * signaled, we can prune the array and recover the
                 * floating references on the fences/requests.
                 */
                prune_fences = count && timeout >= 0;
        } else {
                excl = dma_resv_get_excl_unlocked(resv);
        }

        if (excl && timeout >= 0)
                timeout = i915_gem_object_wait_fence(excl, flags, timeout);

        dma_fence_put(excl);

        /*
         * Opportunistically prune the fences iff we know they have *all* been
         * signaled.
         */
        if (prune_fences)
                dma_resv_prune(resv);

        return timeout;
}

static void fence_set_priority(struct dma_fence *fence,
                               const struct i915_sched_attr *attr)
{
        struct i915_request *rq;
        struct intel_engine_cs *engine;

        if (dma_fence_is_signaled(fence) || !dma_fence_is_i915(fence))
                return;

        rq = to_request(fence);
        engine = rq->engine;

        rcu_read_lock(); /* RCU serialisation for set-wedged protection */
        if (engine->schedule)
                engine->schedule(rq, attr);
        rcu_read_unlock();
}

static inline bool __dma_fence_is_chain(const struct dma_fence *fence)
{
        return fence->ops == &dma_fence_chain_ops;
}

void i915_gem_fence_wait_priority(struct dma_fence *fence,
                                  const struct i915_sched_attr *attr)
{
        if (dma_fence_is_signaled(fence))
                return;

        local_bh_disable();

        /* Recurse once into a fence-array */
        if (dma_fence_is_array(fence)) {
                struct dma_fence_array *array = to_dma_fence_array(fence);
                int i;

                for (i = 0; i < array->num_fences; i++)
                        fence_set_priority(array->fences[i], attr);
        } else if (__dma_fence_is_chain(fence)) {
                struct dma_fence *iter;

                /* The chain is ordered; if we boost the last, we boost all */
                dma_fence_chain_for_each(iter, fence) {
                        fence_set_priority(to_dma_fence_chain(iter)->fence,
                                           attr);
                        break;
                }
                dma_fence_put(iter);
        } else {
                fence_set_priority(fence, attr);
        }

        local_bh_enable(); /* kick the tasklets if queues were reprioritised */
}

int
i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
                              unsigned int flags,
                              const struct i915_sched_attr *attr)
{
        struct dma_fence *excl;

        if (flags & I915_WAIT_ALL) {
                struct dma_fence **shared;
                unsigned int count, i;
                int ret;

                ret = dma_resv_get_fences(obj->base.resv, &excl, &count,
                                          &shared);
                if (ret)
                        return ret;

                for (i = 0; i < count; i++) {
                        i915_gem_fence_wait_priority(shared[i], attr);
                        dma_fence_put(shared[i]);
                }

                kfree(shared);
        } else {
                excl = dma_resv_get_excl_unlocked(obj->base.resv);
        }

        if (excl) {
                i915_gem_fence_wait_priority(excl, attr);
                dma_fence_put(excl);
        }
        return 0;
}

/**
 * Waits for rendering to the object to be completed
 * @obj: i915 gem object
 * @flags: how to wait (under a lock, for all rendering or just for writes etc)
 * @timeout: how long to wait
 */
int
i915_gem_object_wait(struct drm_i915_gem_object *obj,
                     unsigned int flags,
                     long timeout)
{
        might_sleep();
        GEM_BUG_ON(timeout < 0);

        timeout = i915_gem_object_wait_reservation(obj->base.resv,
                                                   flags, timeout);
        return timeout < 0 ? timeout : 0;
}

static inline unsigned long nsecs_to_jiffies_timeout(const u64 n)
{
        /* nsecs_to_jiffies64() does not guard against overflow */
        if (NSEC_PER_SEC % HZ &&
            div_u64(n, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ)
                return MAX_JIFFY_OFFSET;

        return min_t(u64, MAX_JIFFY_OFFSET, nsecs_to_jiffies64(n) + 1);
}

static unsigned long to_wait_timeout(s64 timeout_ns)
{
        if (timeout_ns < 0)
                return MAX_SCHEDULE_TIMEOUT;

        if (timeout_ns == 0)
                return 0;

        return nsecs_to_jiffies_timeout(timeout_ns);
}

/**
 * i915_gem_wait_ioctl - implements DRM_IOCTL_I915_GEM_WAIT
 * @dev: drm device pointer
 * @data: ioctl data blob
 * @file: drm file pointer
 *
 * Returns 0 if successful, else an error is returned with the remaining time in
 * the timeout parameter.
 *  -ETIME: object is still busy after timeout
 *  -ERESTARTSYS: signal interrupted the wait
 *  -ENONENT: object doesn't exist
 * Also possible, but rare:
 *  -EAGAIN: incomplete, restart syscall
 *  -ENOMEM: damn
 *  -ENODEV: Internal IRQ fail
 *  -E?: The add request failed
 *
 * The wait ioctl with a timeout of 0 reimplements the busy ioctl. With any
 * non-zero timeout parameter the wait ioctl will wait for the given number of
 * nanoseconds on an object becoming unbusy. Since the wait itself does so
 * without holding struct_mutex the object may become re-busied before this
 * function completes. A similar but shorter * race condition exists in the busy
 * ioctl
 */
int
i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
{
        struct drm_i915_gem_wait *args = data;
        struct drm_i915_gem_object *obj;
        ktime_t start;
        long ret;

        if (args->flags != 0)
                return -EINVAL;

        obj = i915_gem_object_lookup(file, args->bo_handle);
        if (!obj)
                return -ENOENT;

        start = ktime_get();

        ret = i915_gem_object_wait(obj,
                                   I915_WAIT_INTERRUPTIBLE |
                                   I915_WAIT_PRIORITY |
                                   I915_WAIT_ALL,
                                   to_wait_timeout(args->timeout_ns));

        if (args->timeout_ns > 0) {
                args->timeout_ns -= ktime_to_ns(ktime_sub(ktime_get(), start));
                if (args->timeout_ns < 0)
                        args->timeout_ns = 0;

                /*
                 * Apparently ktime isn't accurate enough and occasionally has a
                 * bit of mismatch in the jiffies<->nsecs<->ktime loop. So patch
                 * things up to make the test happy. We allow up to 1 jiffy.
                 *
                 * This is a regression from the timespec->ktime conversion.
                 */
                if (ret == -ETIME && !nsecs_to_jiffies(args->timeout_ns))
                        args->timeout_ns = 0;

                /* Asked to wait beyond the jiffie/scheduler precision? */
                if (ret == -ETIME && args->timeout_ns)
                        ret = -EAGAIN;
        }

        i915_gem_object_put(obj);
        return ret;
}