drm/radeon: some r420s have a CP race with the DMA engine.

This patch makes sure the CP doesn't DMA do VRAM while 2D
is active by inserting a CP resync token.

todo: port to kms.

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_cp.c b/drivers/gpu/drm/radeon/radeon_cp.c
index fa063d0cfb63..4f7afc79dd82 100644
--- a/drivers/gpu/drm/radeon/radeon_cp.c
+++ b/drivers/gpu/drm/radeon/radeon_cp.c
@@ -616,6 +616,18 @@ static void radeon_do_cp_start(drm_radeon_private_t * dev_priv)
 
         dev_priv->cp_running = 1;
 
+        /* on r420, any DMA from CP to system memory while 2D is active
+         * can cause a hang.  workaround is to queue a CP RESYNC token
+         */
+        if ((dev_priv->flags & RADEON_FAMILY_MASK) == CHIP_R420) {
+                BEGIN_RING(3);
+                OUT_RING(CP_PACKET0(R300_CP_RESYNC_ADDR, 1));
+                OUT_RING(5); /* scratch reg 5 */
+                OUT_RING(0xdeadbeef);
+                ADVANCE_RING();
+                COMMIT_RING();
+        }
+
         BEGIN_RING(8);
         /* isync can only be written through cp on r5xx write it here */
         OUT_RING(CP_PACKET0(RADEON_ISYNC_CNTL, 0));
@@ -653,8 +665,19 @@ static void radeon_do_cp_reset(drm_radeon_private_t * dev_priv)
  */
 static void radeon_do_cp_stop(drm_radeon_private_t * dev_priv)
 {
+        RING_LOCALS;
         DRM_DEBUG("\n");
 
+        /* finish the pending CP_RESYNC token */
+        if ((dev_priv->flags & RADEON_FAMILY_MASK) == CHIP_R420) {
+                BEGIN_RING(2);
+                OUT_RING(CP_PACKET0(R300_RB3D_DSTCACHE_CTLSTAT, 0));
+                OUT_RING(R300_RB3D_DC_FINISH);
+                ADVANCE_RING();
+                COMMIT_RING();
+                radeon_do_wait_for_idle(dev_priv);
+        }
+
         RADEON_WRITE(RADEON_CP_CSQ_CNTL, RADEON_CSQ_PRIDIS_INDDIS);
 
         dev_priv->cp_running = 0;