diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c
index 1741af86943c..f56e65579835 100644
--- a/drivers/gpu/drm/radeon/r600.c
+++ b/drivers/gpu/drm/radeon/r600.c
@@ -3302,6 +3302,10 @@ int r600_irq_process(struct radeon_device *rdev)
 	if (!rdev->ih.enabled || rdev->shutdown)
 		return IRQ_NONE;
 
+	/* No MSIs, need a dummy read to flush PCI DMAs */
+	if (!rdev->msi_enabled)
+		RREG32(IH_RB_WPTR);
+
 	wptr = r600_get_ih_wptr(rdev);
 	rptr = rdev->ih.rptr;
 	DRM_DEBUG("r600_irq_process start: rptr %d, wptr %d\n", rptr, wptr);