Date: Mon, 29 Nov 2004 10:40:07 -0500
From: Dave Jones <davej@redhat.com>
To: Gerd Knorr <kraxel@bytesex.org>
Cc: pawfen@wp.pl, Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: MTRR vesafb and wrong X performance
Message-ID: <20041129154006.GB3898@redhat.com>
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	Gerd Knorr <kraxel@bytesex.org>, pawfen@wp.pl,
	Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
References: <1101338139.1780.9.camel@PC3.dom.pl> <20041124171805.0586a5a1.akpm@osdl.org> <1101419803.1764.23.camel@PC3.dom.pl> <87is7ogb93.fsf@bytesex.org>
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On Mon, Nov 29, 2004 at 12:12:08PM +0100, Gerd Knorr wrote:
 > > > Please send the full dmesg output and the contents of /proc/mtrr for
 > > > 2.6.10-rc2.
 > > reg02: base=0xe3000000 (3632MB), size=   4MB: write-combining, count=1
 > > vesafb: framebuffer at 0xe3000000, mapped to 0xcc880000, using 1875k,
 > > total 4096k
 > 
 > The BIOS reports 4MB video memory, and vesafb adds an mtrr entry for
 > that.  Looks ok, with the exception that the reported 4MB are probably
 > not correct, otherwise the X-Server wouldn't complain.

vesafb is assuming that the memory used in the current screen mode
xres*yres*depth rounded up to nearest power of 2, is the amount of
ram the card has, which is not just wrong, it's dumb.

 > vesafb in 2.6.10-rc2 has a option to overwrite the BIOS-reported value
 > (vtotal=n, with n in megabytes), that should fix it.

which is an ugly hack for the above problem imo.
vesafb:nomtrr also fixes the problem, and leaves X free
to set things up correctly in my experience.

If vesafb can't get it right, maybe it shouldn't be
attempted to do it in the half-assed way it currently does.

		Dave

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