From b586640141ab5f4ab3b194419bc2c0f039e91dbc Mon Sep 17 00:00:00 2001
From: Paul Menzel <paulepanter@users.sourceforge.net>
Date: Tue, 16 Jun 2009 15:34:37 -0700
Subject: [PATCH] intelfb: fix a bug when changing video timing
When changing video timing dynamically via fbset the screen sporadically
is rendered black.
With the attached fix which disables VCO prior to timing register change
the problem disappears.
I had a look at the Xserver register setup code. Here the VCO is
disabled in the same way [1].
This patch is taken from vga-sync-field version 0.0.11 [2][3].
[1] http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/tree/src/i830_=
driver.c
[2] http://lowbyte.de/vga-sync-fields/vga-sync-fields-0.0.11.tgz
[3] http://easy-vdr.de/git?p=frc.git/.git;a=commit;h=dcc3b863e5a663652587619c357bd20075af6896
2587619c357bd20075af6896
Signed-off-by: Thomas Hilber <sparkie@lowbyte.de>
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/video/intelfb/intelfbdrv.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/video/intelfb/intelfbdrv.c b/drivers/video/intelfb/intelfbdrv.c
index ace14fe02fc4..0cafd642fbc0 100644
--- a/drivers/video/intelfb/intelfbdrv.c
+++ b/drivers/video/intelfb/intelfbdrv.c
@@ -1365,6 +1365,11 @@ static int intelfb_set_par(struct fb_info *info)
DBG_MSG("intelfb_set_par (%dx%d-%d)\n", info->var.xres,
info->var.yres, info->var.bits_per_pixel);
+ /*
+ * Disable VCO prior to timing register change.
+ */
+ OUTREG(DPLL_A, INREG(DPLL_A) & ~DPLL_VCO_ENABLE);
+
intelfb_blank(FB_BLANK_POWERDOWN, info);
if (ACCEL(dinfo, info))
--
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