Re: [BUG] VGA palette corruption in vgacon.c for EFI machine

From: Andrew Morton
Date: Tue Jan 04 2011 - 20:06:12 EST

On Fri, 26 Nov 2010 09:44:51 -0500
Yannick Heneault <yannick_heneault@xxxxxxxxxx> wrote:

> Hi,
> It seems there is a small problem of VGA palette corruption on EFI
> machine. When the kernel initializes the architecture, it checks if the
> machine is a EFI machine and if the memory at 0xa0000 is not tagged as
> conventional memory, which should not be the case because this is VGA
> memory. In that case, the kernel assumes that a VGA console can exist. I
> would think that this assumption is correct.
> When the kernel initialize the console in vgacon_startup it checks if it
> can really use the VGA console. I think this is where a check is
> missing. Currently, the function can fail if a VESA boot mode is
> detected but not if a EFI boot mode was used. I think the code should be
> modified like this :
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -377,7 +377,8 @@ static const char *vgacon_startup(void)
> u16 saved1, saved2;
> volatile u16 *p;
> - if (screen_info.orig_video_isVGA == VIDEO_TYPE_VLFB) {
> + if (screen_info.orig_video_isVGA == VIDEO_TYPE_VLFB ||
> + screen_info.orig_video_isVGA == VIDEO_TYPE_EFI) {
> no_vga:
> conswitchp = &dummy_con;
> In that case, the VGA console will fail and a dummy console will be
> temporary used until the EFI driver get loaded. At that point the
> console will be mapped to the EFI driver and graphics (splash screen and
> penguins) will appear correctly.
> Currently, the function vgacon_startup doesn't fail and initialize the
> video card for a real VGA mode. This function change the first 16
> entries of the VGA palette. When the efifb driver kick-in, the palette
> is not restored to default ramp value, thus the 16 first entry remain in
> a modified state.

If that fix worked for you then please send it as a formal, tested,
signed-off kernel patch and we'll put it in the pipeline and see what
emerges from the other end.

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