drm/radeon: Avoid double gpu reset by adding a timeout on IB ring tests.

When the radeon driver resets a gpu, it attempts to test whether all the
rings can successfully handle an IB. If these rings fail to respond, the
process will wait forever. Another gpu reset can't happen at this point,
as the current reset holds a lock required to do so. Instead, make all
the IB tests run with a timeout, so the system can attempt to recover
in this case.

While this doesn't fix the underlying issue with card resets failing, it
gives the system a higher chance of recovering. These timeouts have been
confirmed to help both a Tathi and Hawaii card recover after a gpu reset.

This also adds a new function, radeon_fence_wait_timeout, that behaves like
fence_wait_timeout. It is used instead of fence_wait_timeout as it continues
to work during a reset. radeon_fence_wait is changed to be implemented
using this function.

V2:
- Changed the timeout to 1s, as the default 10s from radeon_wait_timeout was
too long. A timeout of 100ms was tested and found to be too short.
- Changed radeon_fence_wait_timeout to behave more like fence_wait_timeout.

Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Matthew Dawson <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/cik.c

···
 		DRM_ERROR("radeon: failed to schedule ib (%d).\n", r);
 		return r;
 	}
-	r = radeon_fence_wait(ib.fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(ib.fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		radeon_scratch_free(rdev, scratch);
 		radeon_ib_free(rdev, &ib);
 		return r;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		radeon_scratch_free(rdev, scratch);
+		radeon_ib_free(rdev, &ib);
+		return -ETIMEDOUT;
 	}
+	r = 0;
 	for (i = 0; i < rdev->usec_timeout; i++) {
 		tmp = RREG32(scratch);
 		if (tmp == 0xDEADBEEF)

drivers/gpu/drm/radeon/cik_sdma.c

···
 		DRM_ERROR("radeon: failed to schedule ib (%d).\n", r);
 		return r;
 	}
-	r = radeon_fence_wait(ib.fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(ib.fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		return r;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		return -ETIMEDOUT;
 	}
+	r = 0;
 	for (i = 0; i < rdev->usec_timeout; i++) {
 		tmp = le32_to_cpu(rdev->wb.wb[index/4]);
 		if (tmp == 0xDEADBEEF)

drivers/gpu/drm/radeon/r100.c

···
 		DRM_ERROR("radeon: failed to schedule ib (%d).\n", r);
 		goto free_ib;
 	}
-	r = radeon_fence_wait(ib.fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(ib.fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		goto free_ib;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		r = -ETIMEDOUT;
+		goto free_ib;
 	}
+	r = 0;
 	for (i = 0; i < rdev->usec_timeout; i++) {
 		tmp = RREG32(scratch);
 		if (tmp == 0xDEADBEEF) {

drivers/gpu/drm/radeon/r600.c

···
 		DRM_ERROR("radeon: failed to schedule ib (%d).\n", r);
 		goto free_ib;
 	}
-	r = radeon_fence_wait(ib.fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(ib.fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		goto free_ib;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		r = -ETIMEDOUT;
+		goto free_ib;
 	}
+	r = 0;
 	for (i = 0; i < rdev->usec_timeout; i++) {
 		tmp = RREG32(scratch);
 		if (tmp == 0xDEADBEEF)

drivers/gpu/drm/radeon/r600_dma.c

···
 		DRM_ERROR("radeon: failed to schedule ib (%d).\n", r);
 		return r;
 	}
-	r = radeon_fence_wait(ib.fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(ib.fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		return r;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		return -ETIMEDOUT;
 	}
+	r = 0;
 	for (i = 0; i < rdev->usec_timeout; i++) {
 		tmp = le32_to_cpu(rdev->wb.wb[index/4]);
 		if (tmp == 0xDEADBEEF)

drivers/gpu/drm/radeon/radeon.h

···
  */
 #define RADEON_MAX_USEC_TIMEOUT			100000	/* 100 ms */
 #define RADEON_FENCE_JIFFIES_TIMEOUT		(HZ / 2)
+#define RADEON_USEC_IB_TEST_TIMEOUT		1000000 /* 1s */
 /* RADEON_IB_POOL_SIZE must be a power of 2 */
 #define RADEON_IB_POOL_SIZE			16
 #define RADEON_DEBUGFS_MAX_COMPONENTS		32
···
 int radeon_fence_emit(struct radeon_device *rdev, struct radeon_fence **fence, int ring);
 void radeon_fence_process(struct radeon_device *rdev, int ring);
 bool radeon_fence_signaled(struct radeon_fence *fence);
+long radeon_fence_wait_timeout(struct radeon_fence *fence, bool interruptible, long timeout);
 int radeon_fence_wait(struct radeon_fence *fence, bool interruptible);
 int radeon_fence_wait_next(struct radeon_device *rdev, int ring);
 int radeon_fence_wait_empty(struct radeon_device *rdev, int ring);

drivers/gpu/drm/radeon/radeon_fence.c

···
 }
 
 /**
+ * radeon_fence_wait_timeout - wait for a fence to signal with timeout
+ *
+ * @fence: radeon fence object
+ * @intr: use interruptible sleep
+ *
+ * Wait for the requested fence to signal (all asics).
+ * @intr selects whether to use interruptable (true) or non-interruptable
+ * (false) sleep when waiting for the fence.
+ * @timeout: maximum time to wait, or MAX_SCHEDULE_TIMEOUT for infinite wait
+ * Returns remaining time if the sequence number has passed, 0 when
+ * the wait timeout, or an error for all other cases.
+ */
+long radeon_fence_wait_timeout(struct radeon_fence *fence, bool intr, long timeout)
+{
+	uint64_t seq[RADEON_NUM_RINGS] = {};
+	long r;
+	int r_sig;
+
+	/*
+	 * This function should not be called on !radeon fences.
+	 * If this is the case, it would mean this function can
+	 * also be called on radeon fences belonging to another card.
+	 * exclusive_lock is not held in that case.
+	 */
+	if (WARN_ON_ONCE(!to_radeon_fence(&fence->base)))
+		return fence_wait(&fence->base, intr);
+
+	seq[fence->ring] = fence->seq;
+	r = radeon_fence_wait_seq_timeout(fence->rdev, seq, intr, timeout);
+	if (r <= 0) {
+		return r;
+	}
+
+	r_sig = fence_signal(&fence->base);
+	if (!r_sig)
+		FENCE_TRACE(&fence->base, "signaled from fence_wait\n");
+	return r;
+}
+
+/**
  * radeon_fence_wait - wait for a fence to signal
  *
  * @fence: radeon fence object
···
  */
 int radeon_fence_wait(struct radeon_fence *fence, bool intr)
 {
-	uint64_t seq[RADEON_NUM_RINGS] = {};
-	long r;
-
-	/*
-	 * This function should not be called on !radeon fences.
-	 * If this is the case, it would mean this function can
-	 * also be called on radeon fences belonging to another card.
-	 * exclusive_lock is not held in that case.
-	 */
-	if (WARN_ON_ONCE(!to_radeon_fence(&fence->base)))
-		return fence_wait(&fence->base, intr);
-
-	seq[fence->ring] = fence->seq;
-	r = radeon_fence_wait_seq_timeout(fence->rdev, seq, intr, MAX_SCHEDULE_TIMEOUT);
-	if (r < 0) {
+	long r = radeon_fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT);
+	if (r > 0) {
+		return 0;
+	} else {
 		return r;
 	}
-
-	r = fence_signal(&fence->base);
-	if (!r)
-		FENCE_TRACE(&fence->base, "signaled from fence_wait\n");
-	return 0;
 }
 
 /**

drivers/gpu/drm/radeon/radeon_vce.c

···
 		goto error;
 	}
 
-	r = radeon_fence_wait(fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		r = -ETIMEDOUT;
 	} else {
-	        DRM_INFO("ib test on ring %d succeeded\n", ring->idx);
+		DRM_INFO("ib test on ring %d succeeded\n", ring->idx);
+		r = 0;
 	}
 error:
 	radeon_fence_unref(&fence);

drivers/gpu/drm/radeon/uvd_v1_0.c

···
 		goto error;
 	}
 
-	r = radeon_fence_wait(fence, false);
-	if (r) {
+	r = radeon_fence_wait_timeout(fence, false, usecs_to_jiffies(
+		RADEON_USEC_IB_TEST_TIMEOUT));
+	if (r < 0) {
 		DRM_ERROR("radeon: fence wait failed (%d).\n", r);
 		goto error;
+	} else if (r == 0) {
+		DRM_ERROR("radeon: fence wait timed out.\n");
+		r = -ETIMEDOUT;
+		goto error;
 	}
+	r = 0;
 	DRM_INFO("ib test on ring %d succeeded\n",  ring->idx);
 error:
 	radeon_fence_unref(&fence);