drm/radeon/kms: match r6xx/r7xx/evergreen asic_reset with previous asics

Don't reset if the engine isn't busy.  This matches the behavior of
previous asics.  Reseting a non-hung block can lead to a hang.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=33272

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

drivers/gpu/drm/radeon/evergreen.c

@@ -2201,6 +2201,9 @@ static int evergreen_gpu_soft_reset(struct radeon_device *rdev)
 	struct evergreen_mc_save save;
 	u32 grbm_reset = 0;
 
+	if (!(RREG32(GRBM_STATUS) & GUI_ACTIVE))
+		return 0;
+
 	dev_info(rdev->dev, "GPU softreset \n");
 	dev_info(rdev->dev, "  GRBM_STATUS=0x%08X\n",
 		RREG32(GRBM_STATUS));

drivers/gpu/drm/radeon/r600.c

@@ -1287,6 +1287,9 @@ int r600_gpu_soft_reset(struct radeon_device *rdev)
 			S_008014_CB2_BUSY(1) | S_008014_CB3_BUSY(1);
 	u32 tmp;
 
+	if (!(RREG32(GRBM_STATUS) & GUI_ACTIVE))
+		return 0;
+
 	dev_info(rdev->dev, "GPU softreset \n");
 	dev_info(rdev->dev, "  R_008010_GRBM_STATUS=0x%08X\n",
 		RREG32(R_008010_GRBM_STATUS));