drm/radeon/kms: add HDP flushing for all GPUs.

rendercheck under kms on r600s was failing due to HDP flushing not happening.

This adds HDP flushing to the object wait function for r100->r700 families.

rendercheck passes basic tests on r600 with this change.

Acked-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index 4e0a804..772bcd8 100644
--- a/drivers/gpu/drm/radeon/r100.c
+++ b/drivers/gpu/drm/radeon/r100.c
@@ -1589,6 +1589,14 @@
 	r100_hdp_reset(rdev);
 }
 
+void r100_hdp_flush(struct radeon_device *rdev)
+{
+	u32 tmp;
+	tmp = RREG32(RADEON_HOST_PATH_CNTL);
+	tmp |= RADEON_HDP_READ_BUFFER_INVALIDATE;
+	WREG32(RADEON_HOST_PATH_CNTL, tmp);
+}
+
 void r100_hdp_reset(struct radeon_device *rdev)
 {
 	uint32_t tmp;