[Xenial SRU/Yakkety] Set write-combining mtrr for vesafb

[Stefan Bader]

Otherwise console can be rather slow on higher resolutions. We
had this in Trusty-Vivid but at some point after that the source
file moved into a different directory. Which likely caused it to
get lost again.

We probably need to be careful to make sure that any Yakkety kernel
post 4.4 still adds it, too.

-Stefan


>From 24924c740ea3c5c15a27f391171fad2ca93582a2 Mon Sep 17 00:00:00 2001
From: Stefan Bader <stefan.bader at canonical.com>
Date: Tue, 21 Apr 2015 14:54:52 +0200
Subject: [PATCH] UBUNTU: SAUCE: vesafb: Set mtrr:3 (write-combining) as
 default

We had this setting from Oneiric to Saucy[1]. In Saucy it was part
of the combined patch to make vesafb a module, which was unnessesary
in Trusty as we moved back to built-in.
Was added back in Trusty but again lost after Vivid.

It will still be possible to disable mtrr by putting
  video=vesafb:nomtrr or video=vesafb:mtrr:<x>
on the kernel command-line but without that knowledge the default
will be noticably slower (especially on higher resolutions).

[1] https://lists.ubuntu.com/archives/kernel-team/2011-May/015600.html

BugLink: http://bugs.launchpad.net/bugs/1605662

(forward-ported from trusty by adapting file location)
Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
---
 drivers/video/vesafb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
index 1c7da3b..d479804 100644
--- a/drivers/video/fbdev/vesafb.c
+++ b/drivers/video/fbdev/vesafb.c
@@ -47,7 +47,7 @@ static struct fb_fix_screeninfo vesafb_fix = {
 };
 
 static int   inverse    __read_mostly;
-static int   mtrr       __read_mostly;		/* disable mtrr */
+static int   mtrr       __read_mostly = 3;	/* enable mtrr write-comb. */
 static int   vram_remap;			/* Set amount of memory to be used */
 static int   vram_total;			/* Set total amount of memory */
 static int   pmi_setpal __read_mostly = 1;	/* pmi for palette changes ??? */
-- 
1.9.1