lkml.org 
[lkml]   [2006]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: 2.6.17-rc1-mm1
    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. 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.
    -
    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/
    \
     
     \ /
      Last update: 2006-04-05 23:21    [W:0.027 / U:0.168 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site