drm/radeon: implement ring saving on reset v4

Try to save whatever is on the rings when
we encounter an lockup.

v2: Fix spelling error. Free saved ring data if reset fails.
    Add documentation for the new functions.
v3: Some more spelling fixes
v4: It doesn't make sense to save anything if all fences
    are signaled

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 126 insertions, 8 deletions

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index 64d39adaad91..6715e4c695fa 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -768,6 +768,10 @@ int radeon_ring_test(struct radeon_device *rdev, struct radeon_ring *cp);
 void radeon_ring_force_activity(struct radeon_device *rdev, struct radeon_ring *ring);
 void radeon_ring_lockup_update(struct radeon_ring *ring);
 bool radeon_ring_test_lockup(struct radeon_device *rdev, struct radeon_ring *ring);
+unsigned radeon_ring_backup(struct radeon_device *rdev, struct radeon_ring *ring,
+                            uint32_t **data);
+int radeon_ring_restore(struct radeon_device *rdev, struct radeon_ring *ring,
+                        unsigned size, uint32_t *data);
 int radeon_ring_init(struct radeon_device *rdev, struct radeon_ring *cp, unsigned ring_size,
                      unsigned rptr_offs, unsigned rptr_reg, unsigned wptr_reg,
                      u32 ptr_reg_shift, u32 ptr_reg_mask, u32 nop);
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index bbd09718e956..0302a9f3e674 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -996,7 +996,12 @@ int radeon_resume_kms(struct drm_device *dev)
 
 int radeon_gpu_reset(struct radeon_device *rdev)
 {
-        int r;
+        unsigned ring_sizes[RADEON_NUM_RINGS];
+        uint32_t *ring_data[RADEON_NUM_RINGS];
+
+        bool saved = false;
+
+        int i, r;
         int resched;
 
         down_write(&rdev->exclusive_lock);
@@ -1005,20 +1010,47 @@ int radeon_gpu_reset(struct radeon_device *rdev)
         resched = ttm_bo_lock_delayed_workqueue(&rdev->mman.bdev);
         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);
+                }
+        }
+
+retry:
         r = radeon_asic_reset(rdev);
         if (!r) {
-                dev_info(rdev->dev, "GPU reset succeed\n");
+                dev_info(rdev->dev, "GPU reset succeeded, trying to resume\n");
                 radeon_resume(rdev);
+        }
 
-                r = radeon_ib_ring_tests(rdev);
-                if (r)
-                        DRM_ERROR("ib ring test failed (%d).\n", r);
+        radeon_restore_bios_scratch_regs(rdev);
+        drm_helper_resume_force_mode(rdev->ddev);
 
-                radeon_restore_bios_scratch_regs(rdev);
-                drm_helper_resume_force_mode(rdev->ddev);
-                ttm_bo_unlock_delayed_workqueue(&rdev->mman.bdev, resched);
+        if (!r) {
+                for (i = 0; i < RADEON_NUM_RINGS; ++i) {
+                        radeon_ring_restore(rdev, &rdev->ring[i],
+                                            ring_sizes[i], ring_data[i]);
+                }
+
+                r = radeon_ib_ring_tests(rdev);
+                if (r) {
+                        dev_err(rdev->dev, "ib ring test failed (%d).\n", r);
+                        if (saved) {
+                                radeon_suspend(rdev);
+                                goto retry;
+                        }
+                }
+        } else {
+                for (i = 0; i < RADEON_NUM_RINGS; ++i) {
+                        kfree(ring_data[i]);
+                }
         }
 
+        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");
diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c
index ce8eb9d5af5d..75cbe4641138 100644
--- a/drivers/gpu/drm/radeon/radeon_ring.c
+++ b/drivers/gpu/drm/radeon/radeon_ring.c
@@ -362,6 +362,88 @@ bool radeon_ring_test_lockup(struct radeon_device *rdev, struct radeon_ring *rin
         return false;
 }
 
+/**
+ * radeon_ring_backup - Back up the content of a ring
+ *
+ * @rdev: radeon_device pointer
+ * @ring: the ring we want to back up
+ *
+ * Saves all unprocessed commits from a ring, returns the number of dwords saved.
+ */
+unsigned radeon_ring_backup(struct radeon_device *rdev, struct radeon_ring *ring,
+                            uint32_t **data)
+{
+        unsigned size, ptr, i;
+        int ridx = radeon_ring_index(rdev, ring);
+
+        /* just in case lock the ring */
+        mutex_lock(&rdev->ring_lock);
+        *data = NULL;
+
+        if (ring->ring_obj == NULL || !ring->rptr_save_reg) {
+                mutex_unlock(&rdev->ring_lock);
+                return 0;
+        }
+
+        /* it doesn't make sense to save anything if all fences are signaled */
+        if (!radeon_fence_count_emitted(rdev, ridx)) {
+                mutex_unlock(&rdev->ring_lock);
+                return 0;
+        }
+
+        /* calculate the number of dw on the ring */
+        ptr = RREG32(ring->rptr_save_reg);
+        size = ring->wptr + (ring->ring_size / 4);
+        size -= ptr;
+        size &= ring->ptr_mask;
+        if (size == 0) {
+                mutex_unlock(&rdev->ring_lock);
+                return 0;
+        }
+
+        /* and then save the content of the ring */
+        *data = kmalloc(size * 4, GFP_KERNEL);
+        for (i = 0; i < size; ++i) {
+                (*data)[i] = ring->ring[ptr++];
+                ptr &= ring->ptr_mask;
+        }
+
+        mutex_unlock(&rdev->ring_lock);
+        return size;
+}
+
+/**
+ * radeon_ring_restore - append saved commands to the ring again
+ *
+ * @rdev: radeon_device pointer
+ * @ring: ring to append commands to
+ * @size: number of dwords we want to write
+ * @data: saved commands
+ *
+ * Allocates space on the ring and restore the previously saved commands.
+ */
+int radeon_ring_restore(struct radeon_device *rdev, struct radeon_ring *ring,
+                        unsigned size, uint32_t *data)
+{
+        int i, r;
+
+        if (!size || !data)
+                return 0;
+
+        /* restore the saved ring content */
+        r = radeon_ring_lock(rdev, ring, size);
+        if (r)
+                return r;
+
+        for (i = 0; i < size; ++i) {
+                radeon_ring_write(ring, data[i]);
+        }
+
+        radeon_ring_unlock_commit(rdev, ring);
+        kfree(data);
+        return 0;
+}
+
 int radeon_ring_init(struct radeon_device *rdev, struct radeon_ring *ring, unsigned ring_size,
                      unsigned rptr_offs, unsigned rptr_reg, unsigned wptr_reg,
                      u32 ptr_reg_shift, u32 ptr_reg_mask, u32 nop)