drm/radeon: avoid deadlock in pm path when waiting for fence

radeon_fence_wait_empty_locked should not trigger GPU reset as no
place where it's call from would benefit from such thing and it
actually lead to a kernel deadlock in case the reset is triggered
from pm codepath. Instead force ring completion in place where it
makes sense or return early in others.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon.h

@@ -231,7 +231,7 @@ void radeon_fence_process(struct radeon_device *rdev, int ring);
 bool radeon_fence_signaled(struct radeon_fence *fence);
 int radeon_fence_wait(struct radeon_fence *fence, bool interruptible);
 int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring);
-void radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring);
+int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring);
 int radeon_fence_wait_any(struct radeon_device *rdev,
 			  struct radeon_fence **fences,
 			  bool intr);

drivers/gpu/drm/radeon/radeon_device.c

@@ -1164,6 +1164,7 @@ int radeon_suspend_kms(struct drm_device *dev, pm_message_t state)
 	struct drm_crtc *crtc;
 	struct drm_connector *connector;
 	int i, r;
+	bool force_completion = false;
 
 	if (dev == NULL || dev->dev_private == NULL) {
 		return -ENODEV;
@@ -1206,8 +1207,16 @@ int radeon_suspend_kms(struct drm_device *dev, pm_message_t state)
 
 	mutex_lock(&rdev->ring_lock);
 	/* wait for gpu to finish processing current batch */
-	for (i = 0; i < RADEON_NUM_RINGS; i++)
-		radeon_fence_wait_empty_locked(rdev, i);
+	for (i = 0; i < RADEON_NUM_RINGS; i++) {
+		r = radeon_fence_wait_empty_locked(rdev, i);
+		if (r) {
+			/* delay GPU reset to resume */
+			force_completion = true;
+		}
+	}
+	if (force_completion) {
+		radeon_fence_driver_force_completion(rdev);
+	}
 	mutex_unlock(&rdev->ring_lock);
 
 	radeon_save_bios_scratch_regs(rdev);

drivers/gpu/drm/radeon/radeon_fence.c

@@ -609,26 +609,20 @@ int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring)
  * Returns 0 if the fences have passed, error for all other cases.
  * Caller must hold ring lock.
  */
-void radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring)
+int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring)
 {
 	uint64_t seq = rdev->fence_drv[ring].sync_seq[ring];
+	int r;
 
-	while(1) {
-		int r;
-		r = radeon_fence_wait_seq(rdev, seq, ring, false, false);
+	r = radeon_fence_wait_seq(rdev, seq, ring, false, false);
+	if (r) {
 		if (r == -EDEADLK) {
-			mutex_unlock(&rdev->ring_lock);
-			r = radeon_gpu_reset(rdev);
-			mutex_lock(&rdev->ring_lock);
-			if (!r)
-				continue;
-		}
-		if (r) {
-			dev_err(rdev->dev, "error waiting for ring to become"
-				" idle (%d)\n", r);
+			return -EDEADLK;
 		}
-		return;
+		dev_err(rdev->dev, "error waiting for ring[%d] to become idle (%d)\n",
+			ring, r);
 	}
+	return 0;
 }
 
 /**
@@ -854,13 +848,17 @@ int radeon_fence_driver_init(struct radeon_device *rdev)
  */
 void radeon_fence_driver_fini(struct radeon_device *rdev)
 {
-	int ring;
+	int ring, r;
 
 	mutex_lock(&rdev->ring_lock);
 	for (ring = 0; ring < RADEON_NUM_RINGS; ring++) {
 		if (!rdev->fence_drv[ring].initialized)
 			continue;
-		radeon_fence_wait_empty_locked(rdev, ring);
+		r = radeon_fence_wait_empty_locked(rdev, ring);
+		if (r) {
+			/* no need to trigger GPU reset as we are unloading */
+			radeon_fence_driver_force_completion(rdev);
+		}
 		wake_up_all(&rdev->fence_queue);
 		radeon_scratch_free(rdev, rdev->fence_drv[ring].scratch_reg);
 		rdev->fence_drv[ring].initialized = false;

drivers/gpu/drm/radeon/radeon_pm.c

@@ -234,7 +234,7 @@ static void radeon_set_power_state(struct radeon_device *rdev)
 
 static void radeon_pm_set_clocks(struct radeon_device *rdev)
 {
-	int i;
+	int i, r;
 
 	/* no need to take locks, etc. if nothing's going to change */
 	if ((rdev->pm.requested_clock_mode_index == rdev->pm.current_clock_mode_index) &&
@@ -248,8 +248,17 @@ static void radeon_pm_set_clocks(struct radeon_device *rdev)
 	/* wait for the rings to drain */
 	for (i = 0; i < RADEON_NUM_RINGS; i++) {
 		struct radeon_ring *ring = &rdev->ring[i];
-		if (ring->ready)
-			radeon_fence_wait_empty_locked(rdev, i);
+		if (!ring->ready) {
+			continue;
+		}
+		r = radeon_fence_wait_empty_locked(rdev, i);
+		if (r) {
+			/* needs a GPU reset dont reset here */
+			mutex_unlock(&rdev->ring_lock);
+			up_write(&rdev->pm.mclk_lock);
+			mutex_unlock(&rdev->ddev->struct_mutex);
+			return;
+		}
 	}
 
 	radeon_unmap_vram_bos(rdev);