drm/radeon: fix AVI infoframe generation

- remove adding 2 to checksum, this is incorrect.

This was incorrectly introduced in:
92db7f6c860b8190571a9dc1fcbc16d003422fe8
http://lists.freedesktop.org/archives/dri-devel/2011-December/017717.html
However, the off by 2 was due to adding the version twice.
From the examples in the URL above:

[Rafał Miłecki][RV620] fglrx:
0x7454: 00 A8 5E 79     R600_HDMI_VIDEOINFOFRAME_0
0x7458: 00 28 00 10     R600_HDMI_VIDEOINFOFRAME_1
0x745C: 00 48 00 28     R600_HDMI_VIDEOINFOFRAME_2
0x7460: 02 00 00 48     R600_HDMI_VIDEOINFOFRAME_3
===================
(0x82 + 0x2 + 0xD) + 0x1F8 = 0x289
-0x289 = 0x77

However, the payload sum is not 0x1f8, it's 0x1f6.
00 + A8 + 5E + 00 +
00 + 28 + 00 + 10 +
00 + 48 + 00 + 28 +
00 + 48 =
0x1f6

Bits 25:24 of HDMI_VIDEOINFOFRAME_3 are the packet version, not part
of the payload.  So the total would be:
(0x82 + 0x2 + 0xD) + 0x1f6 = 0x287
-0x287 = 0x79

- properly emit the AVI infoframe version.  This was not being
emitted previous which is probably what caused the issue above.

This should fix blank screen when HDMI audio is enabled on
certain monitors.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Cc: Rafał Miłecki <zajec5@gmail.com>

1 files changed, 2 insertions, 9 deletions

diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
index 456750a0daa5..e73b2a73494a 100644
--- a/drivers/gpu/drm/radeon/r600_hdmi.c
+++ b/drivers/gpu/drm/radeon/r600_hdmi.c
@@ -133,14 +133,7 @@ static void r600_hdmi_update_avi_infoframe(struct drm_encoder *encoder,
         struct radeon_encoder_atom_dig *dig = radeon_encoder->enc_priv;
         uint32_t offset = dig->afmt->offset;
         uint8_t *frame = buffer + 3;
-
-        /* 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;
+        uint8_t *header = buffer;
 
         WREG32(HDMI0_AVI_INFO0 + offset,
                 frame[0x0] | (frame[0x1] << 8) | (frame[0x2] << 16) | (frame[0x3] << 24));
@@ -149,7 +142,7 @@ static void r600_hdmi_update_avi_infoframe(struct drm_encoder *encoder,
         WREG32(HDMI0_AVI_INFO2 + offset,
                 frame[0x8] | (frame[0x9] << 8) | (frame[0xA] << 16) | (frame[0xB] << 24));
         WREG32(HDMI0_AVI_INFO3 + offset,
-                frame[0xC] | (frame[0xD] << 8));
+                frame[0xC] | (frame[0xD] << 8) | (header[1] << 24));
 }
 
 /*