[PATCH 3.16.y-ckt 075/165] drm/radeon: do a posting read in rs600_set_irq

[Luis Henriques]

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Deucher <alexander.deucher at amd.com>

commit 54acf107e4e66d1f4a697e08a7f60dba9fcf07c3 upstream.

To make sure the writes go through the pci bridge.

bug:
https://bugzilla.kernel.org/show_bug.cgi?id=90741

Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/radeon/rs600.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/radeon/rs600.c b/drivers/gpu/drm/radeon/rs600.c
index d6e64b93d8b1..1016f53f755c 100644
--- a/drivers/gpu/drm/radeon/rs600.c
+++ b/drivers/gpu/drm/radeon/rs600.c
@@ -684,6 +684,10 @@ int rs600_irq_set(struct radeon_device *rdev)
 	WREG32(R_007D18_DC_HOT_PLUG_DETECT2_INT_CONTROL, hpd2);
 	if (ASIC_IS_DCE2(rdev))
 		WREG32(R_007408_HDMI0_AUDIO_PACKET_CONTROL, hdmi0);
+
+	/* posting read */
+	RREG32(R_000040_GEN_INT_CNTL);
+
 	return 0;
 }