intelfb: fix a bug when changing video timing
authorPaul Menzel <paulepanter@users.sourceforge.net>
Tue, 16 Jun 2009 22:34:37 +0000 (15:34 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 17 Jun 2009 02:48:00 +0000 (19:48 -0700)
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

index ace14fe02fc4f49348024b1d1bc964cccffecbdc..0cafd642fbc0f57b5eaee3fe85a60895c30e1d8d 100644 (file)
@@ -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);
 
        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))
        intelfb_blank(FB_BLANK_POWERDOWN, info);
 
        if (ACCEL(dinfo, info))