drm/radeon: reset dma engine on gpu reset (v2)

This try to reset the dma engine when performing gpu reset. Hopefully
bringing back the gpu dma engine in sane state.

v2: agd5f: fix dma reset on cayman/TN, add support for SI

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index 74d3845..4bf1733 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -2129,7 +2129,7 @@
 static int si_gpu_soft_reset(struct radeon_device *rdev)
 {
 	struct evergreen_mc_save save;
-	u32 grbm_reset = 0;
+	u32 grbm_reset = 0, tmp;
 
 	if (!(RREG32(GRBM_STATUS) & GUI_ACTIVE))
 		return 0;
@@ -2159,6 +2159,22 @@
 	/* Disable CP parsing/prefetching */
 	WREG32(CP_ME_CNTL, CP_ME_HALT | CP_PFP_HALT | CP_CE_HALT);
 
+	/* dma0 */
+	tmp = RREG32(DMA_RB_CNTL + DMA0_REGISTER_OFFSET);
+	tmp &= ~DMA_RB_ENABLE;
+	WREG32(DMA_RB_CNTL + DMA0_REGISTER_OFFSET, tmp);
+
+	/* dma1 */
+	tmp = RREG32(DMA_RB_CNTL + DMA1_REGISTER_OFFSET);
+	tmp &= ~DMA_RB_ENABLE;
+	WREG32(DMA_RB_CNTL + DMA1_REGISTER_OFFSET, tmp);
+
+	/* Reset dma */
+	WREG32(SRBM_SOFT_RESET, SOFT_RESET_DMA | SOFT_RESET_DMA1);
+	RREG32(SRBM_SOFT_RESET);
+	udelay(50);
+	WREG32(SRBM_SOFT_RESET, 0);
+
 	/* reset all the gfx blocks */
 	grbm_reset = (SOFT_RESET_CP |
 		      SOFT_RESET_CB |