[PATCH] drm/radeon/kms: workaround invalid AVI infoframe checksum issue

[Rafał Miłecki]

Cc: stable at vger.kernel.org
Signed-off-by: Rafał Miłecki <zajec5 at gmail.com>
---
I'd like to propose taking this patch into older releases. It's really
trivial while it fixes important feature.

This change was verified to fix both issues with no video I've
investigated. I've also checked checksum calculation with fglrx on:
RV620, HD54xx, HD5450, HD6310, HD6320.
---
 drivers/gpu/drm/radeon/r600_hdmi.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
index 5021372..3db76ac 100644
--- a/drivers/gpu/drm/radeon/r600_hdmi.c
+++ b/drivers/gpu/drm/radeon/r600_hdmi.c
@@ -196,6 +196,13 @@ static void r600_hdmi_videoinfoframe(
 	frame[0xD] = (right_bar >> 8);
 
 	r600_hdmi_infoframe_checksum(0x82, 0x02, 0x0D, frame);
+	/* Our header values (type, version, length) should be alright, Intel
+	 * is using the same. Checksum function also seems to be OK, it works
+	 * fine for audio infoframe. However calculated value is always lower
+	 * by 2 in comparison to fglrx. It breaks displaying anything in case
+	 * of TVs that strictly check the checksum. Hack it manually here to
+	 * workaround this issue. */
+	frame[0x0] += 2;
 
 	WREG32(offset+R600_HDMI_VIDEOINFOFRAME_0,
 		frame[0x0] | (frame[0x1] << 8) | (frame[0x2] << 16) | (frame[0x3] << 24));
-- 
1.7.7