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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.
-
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