Messages in this thread |  | | | Date | Wed, 5 Apr 2006 14:37:27 -0700 | | From | Andrew Morton <> | | Subject | Re: 2.6.17-rc1-mm1 |
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"Luck, Tony" <tony.luck@intel.com> wrote: > > On Wed, Apr 05, 2006 at 10:15:34AM -0600, Bjorn Helgaas wrote: > > Huh. Intel firmware used to just not mention the VGA framebuffer > > (0xa0000-0xc0000) at all in the EFI memory map. I think that was > > clearly a bug. So maybe they fixed that by marking it WB (and > > hopefully UC as well). > > Nope ... not fixed (at least not in the f/w that I'm running). The > VGA buffer is still simply not mentioned in the EFI memory map. > > The problem looks to come from this code in vgacon.c: > > vga_vram_base = VGA_MAP_MEM(vga_vram_base); > vga_vram_end = VGA_MAP_MEM(vga_vram_end); > vga_vram_size = vga_vram_end - vga_vram_base; > > vga_vram_base is 0xb8000, and this call gets a UC return of > c0000000000b8000. But vga_vram_end is 0xc0000 ... which is > the address of the start of a block of memory that is both > WB and UC capable.
OK, so it's really an off-by-one error.
> So ioremap() gives us e0000000000c0000 > (which means that vga_vram_size is 2000000000008000, surely > the biggest, baddest video card in the history of the world!). > > Perhaps the right fix is to subtract 1 from vga_vram_end and pass > that into VGA_MAP_MEM(), and then add the 1 byte back when computing > the size? But I don't know whether that might do something bad on > some other architecture that uses vgacon.c. If this is not > acceptable, then we can fall back and use the Nanhai/Bjorn fix > of using ioremap_nocache(). > > Signed-off-by: Tony Luck <tony.luck@intel.com> > > --- > > diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c > index d5a04b6..4ca9877 100644 > --- a/drivers/video/console/vgacon.c > +++ b/drivers/video/console/vgacon.c > @@ -484,8 +484,8 @@ #endif > } > > vga_vram_base = VGA_MAP_MEM(vga_vram_base); > - vga_vram_end = VGA_MAP_MEM(vga_vram_end); > - vga_vram_size = vga_vram_end - vga_vram_base; > + vga_vram_end = VGA_MAP_MEM(vga_vram_end - 1); > + vga_vram_size = vga_vram_end - vga_vram_base + 1; > > /* > * Find out if there is a graphics card present.
Looks like the correct fix to me.
Tony (D), can you think of any problems with that approach? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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