drm/radeon: do a posting read in r100_set_irq

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@amd.com>
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index 40ed0e5b95a3ba0a01101f9f9ba8c02beb162fde..8ec5b855387354149bbdd13148fed1c7ecccd99f 100644 (file)
--- 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;
 }