drm/radeon: rework fence handling, drop fence list v7

Using 64bits fence sequence we can directly compare sequence
number to know if a fence is signaled or not. Thus the fence
list became useless, so does the fence lock that mainly
protected the fence list.

Things like ring.ready are no longer behind a lock, this should
be ok as ring.ready is initialized once and will only change
when facing lockup. Worst case is that we return an -EBUSY just
after a successfull GPU reset, or we go into wait state instead
of returning -EBUSY (thus delaying reporting -EBUSY to fence
wait caller).

v2: Remove left over comment, force using writeback on cayman and
    newer, thus not having to suffer from possibly scratch reg
    exhaustion
v3: Rebase on top of change to uint64 fence patch
v4: Change DCE5 test to force write back on cayman and newer but
    also any APU such as PALM or SUMO family
v5: Rebase on top of new uint64 fence patch
v6: Just break if seq doesn't change any more. Use radeon_fence
    prefix for all function names. Even if it's now highly optimized,
    try avoiding polling to often.
v7: We should never poll the last_seq from the hardware without
    waking the sleeping threads, otherwise we might lose events.
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Christian König <deathsimple@vodafone.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon.h

@@ -263,15 +263,12 @@ struct radeon_fence_driver {
 	atomic64_t			last_seq;
 	unsigned long			last_activity;
 	wait_queue_head_t		queue;
-	struct list_head		emitted;
-	struct list_head		signaled;
 	bool				initialized;
 };
 
 struct radeon_fence {
 	struct radeon_device		*rdev;
 	struct kref			kref;
-	struct list_head		list;
 	/* protected by radeon_fence.lock */
 	uint64_t			seq;
 	/* RB, DMA, etc. */
@@ -291,7 +288,7 @@ int radeon_fence_wait_next(struct radeon_device *rdev, int ring);
 int radeon_fence_wait_empty(struct radeon_device *rdev, int ring);
 struct radeon_fence *radeon_fence_ref(struct radeon_fence *fence);
 void radeon_fence_unref(struct radeon_fence **fence);
-int radeon_fence_count_emitted(struct radeon_device *rdev, int ring);
+unsigned radeon_fence_count_emitted(struct radeon_device *rdev, int ring);
 
 /*
  * Tiling registers
@@ -1534,7 +1531,6 @@ struct radeon_device {
 	struct radeon_mode_info		mode_info;
 	struct radeon_scratch		scratch;
 	struct radeon_mman		mman;
-	rwlock_t			fence_lock;
 	struct radeon_fence_driver	fence_drv[RADEON_NUM_RINGS];
 	struct radeon_semaphore_driver	semaphore_drv;
 	struct mutex			ring_lock;

drivers/gpu/drm/radeon/radeon_device.c

@@ -225,9 +225,9 @@ int radeon_wb_init(struct radeon_device *rdev)
 	/* disable event_write fences */
 	rdev->wb.use_event = false;
 	/* disabled via module param */
-	if (radeon_no_wb == 1)
+	if (radeon_no_wb == 1) {
 		rdev->wb.enabled = false;
-	else {
+	} else {
 		if (rdev->flags & RADEON_IS_AGP) {
 			/* often unreliable on AGP */
 			rdev->wb.enabled = false;
@@ -237,8 +237,9 @@ int radeon_wb_init(struct radeon_device *rdev)
 		} else {
 			rdev->wb.enabled = true;
 			/* event_write fences are only available on r600+ */
-			if (rdev->family >= CHIP_R600)
+			if (rdev->family >= CHIP_R600) {
 				rdev->wb.use_event = true;
+			}
 		}
 	}
 	/* always use writeback/events on NI, APUs */
@@ -731,7 +732,6 @@ int radeon_device_init(struct radeon_device *rdev,
 	mutex_init(&rdev->gem.mutex);
 	mutex_init(&rdev->pm.mutex);
 	mutex_init(&rdev->vram_mutex);
-	rwlock_init(&rdev->fence_lock);
 	rwlock_init(&rdev->semaphore_drv.lock);
 	INIT_LIST_HEAD(&rdev->gem.objects);
 	init_waitqueue_head(&rdev->irq.vblank_queue);