1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/gpu/drm/radeon/r300.c b/drivers/gpu/drm/radeon/r300.c
index 3f2cc9e2e8d9..b8623b734a27 100644
--- a/drivers/gpu/drm/radeon/r300.c
+++ b/drivers/gpu/drm/radeon/r300.c
@@ -36,7 +36,15 @@
 #include "rv350d.h"
 #include "r300_reg_safe.h"
 
-/* This files gather functions specifics to: r300,r350,rv350,rv370,rv380 */
+/* This files gather functions specifics to: r300,r350,rv350,rv370,rv380
+ *
+ * GPU Errata:
+ * - HOST_PATH_CNTL: r300 family seems to dislike write to HOST_PATH_CNTL
+ *   using MMIO to flush host path read cache, this lead to HARDLOCKUP.
+ *   However, scheduling such write to the ring seems harmless, i suspect
+ *   the CP read collide with the flush somehow, or maybe the MC, hard to
+ *   tell. (Jerome Glisse)
+ */
 
 /*
  * rv370,rv380 PCIE GART
@@ -178,6 +186,11 @@ void r300_fence_ring_emit(struct radeon_device *rdev,
         /* Wait until IDLE & CLEAN */
         radeon_ring_write(rdev, PACKET0(0x1720, 0));
         radeon_ring_write(rdev, (1 << 17) | (1 << 16)  | (1 << 9));
+        radeon_ring_write(rdev, PACKET0(RADEON_HOST_PATH_CNTL, 0));
+        radeon_ring_write(rdev, rdev->config.r300.hdp_cntl |
+                                RADEON_HDP_READ_BUFFER_INVALIDATE);
+        radeon_ring_write(rdev, PACKET0(RADEON_HOST_PATH_CNTL, 0));
+        radeon_ring_write(rdev, rdev->config.r300.hdp_cntl);
         /* Emit fence sequence & fire IRQ */
         radeon_ring_write(rdev, PACKET0(rdev->fence_drv.scratch_reg, 0));
         radeon_ring_write(rdev, fence->seq);
@@ -1258,6 +1271,7 @@ static int r300_startup(struct radeon_device *rdev)
         }
         /* Enable IRQ */
         r100_irq_set(rdev);
+        rdev->config.r300.hdp_cntl = RREG32(RADEON_HOST_PATH_CNTL);
         /* 1M ring buffer */
         r = r100_cp_init(rdev, 1024 * 1024);
         if (r) {