[PATCH 3.4 064/172] drm/radeon: do a posting read in r100_set_irq

[lizf]

From: Alex Deucher <alexander.deucher@xxxxxxx>

3.4.108-rc1 review patch.  If anyone has any objections, please let me know.

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


commit f957063fee6392bb9365370db6db74dc0b2dce0a 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@xxxxxxx>
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
 drivers/gpu/drm/radeon/r100.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index 40ed0e5..8ec5b85 100644
--- a/drivers/gpu/drm/radeon/r100.c
+++ b/drivers/gpu/drm/radeon/r100.c
@@ -726,6 +726,10 @@ int r100_irq_set(struct radeon_device *rdev)
 		tmp |= RADEON_FP2_DETECT_MASK;
 	}
 	WREG32(RADEON_GEN_INT_CNTL, tmp);
+
+	/* read back to post the write */
+	RREG32(RADEON_GEN_INT_CNTL);
+
 	return 0;
 }
 
-- 
1.9.1

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