[PATCH 1/3] drm/radeon: take exclusive_lock in read mode during ring tests, v2

[Maarten Lankhorst <maarten.lankhorst@canonical.com>]

This is needed for the next commit, because the lockup detection
will need the read lock to run.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
---
Changes since v1:

Changed order of resuming a bit according to ckoenig's feedback.

Reset handling seems just as unreliable as before this commit,
but at least it restores mode correctly now. :-)

 drivers/gpu/drm/radeon/radeon.h        |  2 +-
 drivers/gpu/drm/radeon/radeon_device.c | 64 ++++++++++++++++++++--------------
 2 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index 9e1732eb402c..1d806983ec7b 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -2312,7 +2312,7 @@ struct radeon_device {
 	bool				need_dma32;
 	bool				accel_working;
 	bool				fastfb_working; /* IGP feature*/
-	bool				needs_reset;
+	bool				needs_reset, in_reset;
 	struct radeon_surface_reg surface_regs[RADEON_GEM_MAX_SURFACES];
 	const struct firmware *me_fw;	/* all family ME firmware */
 	const struct firmware *pfp_fw;	/* r6/700 PFP firmware */
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index c8ea050c8fa4..0e9541acccd5 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1671,29 +1671,35 @@ int radeon_gpu_reset(struct radeon_device *rdev)
 	down_write(&rdev->exclusive_lock);
 
 	if (!rdev->needs_reset) {
+		WARN_ON(rdev->in_reset);
 		up_write(&rdev->exclusive_lock);
 		return 0;
 	}
 
 	rdev->needs_reset = false;
+	resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);
 
-	radeon_save_bios_scratch_regs(rdev);
 	/* block TTM */
-	resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);
 	radeon_pm_suspend(rdev);
-	radeon_suspend(rdev);
 
-	for (i = 0; i < RADEON_NUM_RINGS; ++i) {
-		ring_sizes[i] = radeon_ring_backup(rdev, &rdev->ring[i],
-						   &ring_data[i]);
-		if (ring_sizes[i]) {
-			saved = true;
-			dev_info(rdev->dev, "Saved %d dwords of commands "
-				 "on ring %d.\n", ring_sizes[i], i);
+	if (!rdev->in_reset) {
+		rdev->in_reset = true;
+
+		radeon_save_bios_scratch_regs(rdev);
+		radeon_suspend(rdev);
+
+		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
+			ring_sizes[i] = radeon_ring_backup(rdev, &rdev->ring[i],
+							   &ring_data[i]);
+			if (ring_sizes[i]) {
+				saved = true;
+				dev_info(rdev->dev, "Saved %d dwords of commands "
+					 "on ring %d.\n", ring_sizes[i], i);
+			}
 		}
-	}
+	} else
+		memset(ring_data, 0, sizeof(ring_data));
 
-retry:
 	r = radeon_asic_reset(rdev);
 	if (!r) {
 		dev_info(rdev->dev, "GPU reset succeeded, trying to resume\n");
@@ -1701,41 +1707,47 @@ retry:
 	}
 
 	radeon_restore_bios_scratch_regs(rdev);
+	radeon_pm_resume(rdev);
 
-	if (!r) {
+	if (!r && saved) {
 		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
 			radeon_ring_restore(rdev, &rdev->ring[i],
 					    ring_sizes[i], ring_data[i]);
-			ring_sizes[i] = 0;
 			ring_data[i] = NULL;
 		}
+	} else {
+		radeon_fence_driver_force_completion(rdev);
 
+		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
+			kfree(ring_data[i]);
+		}
+	}
+
+	drm_helper_resume_force_mode(rdev->ddev);
+	ttm_bo_unlock_delayed_workqueue(&rdev->mman.bdev, resched);
+	downgrade_write(&rdev->exclusive_lock);
+
+	if (!r) {
 		r = radeon_ib_ring_tests(rdev);
 		if (r) {
 			dev_err(rdev->dev, "ib ring test failed (%d).\n", r);
 			if (saved) {
-				saved = false;
+				/* if reset fails, try without saving data */
+				rdev->needs_reset = true;
 				radeon_suspend(rdev);
-				goto retry;
+				up_read(&rdev->exclusive_lock);
+				return -EAGAIN;
 			}
 		}
-	} else {
-		radeon_fence_driver_force_completion(rdev);
-		for (i = 0; i < RADEON_NUM_RINGS; ++i) {
-			kfree(ring_data[i]);
-		}
 	}
 
-	radeon_pm_resume(rdev);
-	drm_helper_resume_force_mode(rdev->ddev);
-
-	ttm_bo_unlock_delayed_workqueue(&rdev->mman.bdev, resched);
 	if (r) {
 		/* bad news, how to tell it to userspace ? */
 		dev_info(rdev->dev, "GPU reset failed\n");
 	}
 
-	up_write(&rdev->exclusive_lock);
+	rdev->in_reset = false;
+	up_read(&rdev->exclusive_lock);
 	return r;
 }
 
-- 
2.0.4