linux-kernel - Re: vga and 64-bit memcpy's

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Message-ID: <CAPM=9tzuHQxPYoUZegKzwUoHBvp1UTkmtV3zcBmUxeJUr9qAWA@mail.gmail.com>
Date:	Fri, 12 Sep 2014 20:48:01 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: vga and 64-bit memcpy's

On 12 September 2014 20:26, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Fri, 12 Sep 2014 13:57:20 +1000
> Dave Airlie <airlied@...il.com> wrote:
>
>> Got an bug report from someone using a silicon motion video card in
>> VGA mode about corruption that they tracked down to 64-bit memory
>> operations not being supported by the video card, it appears that we
>> probably shouldn't be using > 32-bit copies on VGA memory.
>
> VGA memory is write combining usually so the answer in general would be
> no. You may also find its a combination of bridge and card and one or the
> other is somehow out of spec.

Well I'm not shocked that an SMI GPU is out of spec, just not sure how
we can workaround it.

Dave.
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