linux-kernel - [20/48] drm/radeon/kms: workaround invalid AVI infoframe checksum issue

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Message-Id: <20120116184517.476961050@clark.kroah.org>
Date:	Mon, 16 Jan 2012 10:44:47 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Rafał Miłecki <zajec5@...il.com>,
	Dave Airlie <airlied@...hat.com>
Subject: [20/48] drm/radeon/kms: workaround invalid AVI infoframe checksum issue

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

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

From: Rafał Miłecki <zajec5@...il.com>

commit 92db7f6c860b8190571a9dc1fcbc16d003422fe8 upstream.

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.

Signed-off-by: Rafał Miłecki <zajec5@...il.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/gpu/drm/radeon/r600_hdmi.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- 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));


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