drm/r600/kms: fixup number of loops per blit calculation.

Some people were seeing
*ERROR* radeon: writting more dword to ring than expected
after certain blits, the loops calculation didn't take
into account that we do a separate blit for the remainder
after doing the aligned blits.

Acked-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 14 insertions, 7 deletions

diff --git a/drivers/gpu/drm/radeon/r600_blit_kms.c b/drivers/gpu/drm/radeon/r600_blit_kms.c
index 4f0d181a690..1287f4d3fb2 100644
--- a/drivers/gpu/drm/radeon/r600_blit_kms.c
+++ b/drivers/gpu/drm/radeon/r600_blit_kms.c
@@ -548,10 +548,13 @@ void r600_vb_ib_put(struct radeon_device *rdev)
 int r600_blit_prepare_copy(struct radeon_device *rdev, int size_bytes)
 {
         int r;
-        int ring_size;
+        int ring_size, line_size;
         int max_size;
         /* loops of emits 64 + fence emit possible */
-        int dwords_per_loop = 76;
+        int dwords_per_loop = 76, num_loops;
+
+        r = r600_vb_ib_get(rdev);
+        WARN_ON(r);
 
         /* set_render_target emits 2 extra dwords on rv6xx */
         if (rdev->family > CHIP_R600 && rdev->family < CHIP_RV770)
@@ -559,14 +562,18 @@ int r600_blit_prepare_copy(struct radeon_device *rdev, int size_bytes)
 
         /* 8 bpp vs 32 bpp for xfer unit */
         if (size_bytes & 3)
-                max_size = 8192*8192;
+                line_size = 8192;
         else
-                max_size = 8192*8192*4;
+                line_size = 8192*4;
 
-        r = r600_vb_ib_get(rdev);
-        WARN_ON(r);
+        max_size = 8192 * line_size;
 
-        ring_size = ((size_bytes + max_size) / max_size) * dwords_per_loop;
+        /* major loops cover the max size transfer */
+        num_loops = ((size_bytes + max_size) / max_size);
+        /* minor loops cover the extra non aligned bits */
+        num_loops += ((size_bytes % line_size) ? 1 : 0);
+        /* calculate number of loops correctly */
+        ring_size = num_loops * dwords_per_loop;
         /* set default  + shaders */
         ring_size += 40; /* shaders + def state */
         ring_size += 3; /* fence emit for VB IB */