[PATCH] vesafb: Document mtrr boot option usage

Document mtrr boot option usage to Documentation/fb/vesafb.txt.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/fb/vesafb.txt b/Documentation/fb/vesafb.txt
index 814e2f56a6ad35ce367e2d542769664c8b6641f3..62db6758d1c1050db42b638ad4d42dc06809c68b 100644 (file)
--- a/Documentation/fb/vesafb.txt
+++ b/Documentation/fb/vesafb.txt
@@ -144,7 +144,21 @@ vgapal     Use the standard vga registers for palette changes.
        This is the default.
 pmipal Use the protected mode interface for palette changes.
 
-mtrr   setup memory type range registers for the vesafb framebuffer.
+mtrr:n setup memory type range registers for the vesafb framebuffer
+       where n:
+             0 - disabled (equivalent to nomtrr)
+             1 - uncachable
+             2 - write-back
+             3 - write-combining (default)
+             4 - write-through
+
+       If you see the following in dmesg, choose the type that matches the
+       old one. In this example, use "mtrr:2".
+...
+mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining
+...
+
+nomtrr  disable mtrr
 
 vremap:n
         remap 'n' MiB of video RAM. If 0 or not specified, remap memory