linux-kernel - [PATCH 119/150] KMS: fix EDID detailed timing vsync parsing

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Message-Id: <1364311249-14454-120-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 26 Mar 2013 15:20:18 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Torsten Duwe <duwe@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 119/150] KMS: fix EDID detailed timing vsync parsing

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

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

From: Torsten Duwe <torsten@....de>

commit 16dad1d743d31a104a849c8944e6b9eb479f6cd7 upstream.

EDID spreads some values across multiple bytes; bit-fiddling is needed
to retrieve these.  The current code to parse "detailed timings" has a
cut&paste error that results in a vsync offset of at most 15 lines
instead of 63.

See

   http://en.wikipedia.org/wiki/EDID

and in the "EDID Detailed Timing Descriptor" see bytes 10+11 show why
that needs to be a left shift.

Signed-off-by: Torsten Duwe <duwe@....de>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/drm_edid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 74f2421..f689958 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -876,7 +876,7 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_device *dev,
 	unsigned vblank = (pt->vactive_vblank_hi & 0xf) << 8 | pt->vblank_lo;
 	unsigned hsync_offset = (pt->hsync_vsync_offset_pulse_width_hi & 0xc0) << 2 | pt->hsync_offset_lo;
 	unsigned hsync_pulse_width = (pt->hsync_vsync_offset_pulse_width_hi & 0x30) << 4 | pt->hsync_pulse_width_lo;
-	unsigned vsync_offset = (pt->hsync_vsync_offset_pulse_width_hi & 0xc) >> 2 | pt->vsync_offset_pulse_width_lo >> 4;
+	unsigned vsync_offset = (pt->hsync_vsync_offset_pulse_width_hi & 0xc) << 2 | pt->vsync_offset_pulse_width_lo >> 4;
 	unsigned vsync_pulse_width = (pt->hsync_vsync_offset_pulse_width_hi & 0x3) << 4 | (pt->vsync_offset_pulse_width_lo & 0xf);
 
 	/* ignore tiny modes */
-- 
1.8.1.2

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