vesafb: Document mtrr boot option usage

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

From: Antonino Daplas <[email protected]>

---

vesafb.txt | 16 +++++++++++++++-

1 files changed, 15 insertions(+), 1 deletion(-)

@@ -144,7 +144,21 @@ vgapal	Use the standard vga registers fo

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

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