linux-kernel - [ 102/104] KMS: fix EDID detailed timing vsync parsing

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Message-Id: <20130325010534.420002557@decadent.org.uk>
Date:	Mon, 25 Mar 2013 01:07:06 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, Torsten Duwe <torsten@....de>,
	Torsten Duwe <duwe@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 102/104] KMS: fix EDID detailed timing vsync parsing

3.2-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: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/drm_edid.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -852,7 +852,7 @@ static struct drm_display_mode *drm_mode
 	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 */


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