From: Brice Goglin <brice.goglin@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
David Airlie <airlied@linux.ie>,
dri-devel@lists.freedesktop.org
Subject: Re: MTRR use in drivers
Date: Sun, 23 Jun 2013 08:35:30 +0200 [thread overview]
Message-ID: <51C69732.1010906@gmail.com> (raw)
In-Reply-To: <51C3DDFA.7050204@zytor.com>
Le 21/06/2013 07:00, H. Peter Anvin a écrit :
> An awful lot of drivers, mostly DRI drivers, are still mucking with
> MTRRs directly as opposed to using ioremap_wc() or similar interfaces.
> In addition to the architecture dependency, this is really undesirable
> because MTRRs are a limited resource, whereas page table attributes are not.
>
> Furthermore, this perpetuates the need for the horrific hack known as
> "MTRR cleanup".
>
> What, if anything, can we do to clean up this mess?
>
> -hpa
>
The first network driver that used ioremap_wc() back in 2008 (myri10ge)
had to keep using MTRR because ioremap_wc() silently falls back to
ioremap_nocache() when PAT is disabled.
I asked about this in https://lkml.org/lkml/2008/5/31/42 and there was
some talk about putting the MTRR addition in the nocache fallback path
but I guess nobody implemented the idea.
Brice
next prev parent reply other threads:[~2013-06-23 6:35 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-21 5:00 MTRR use in drivers H. Peter Anvin
2013-06-23 6:35 ` Brice Goglin [this message]
2013-06-23 14:07 ` H. Peter Anvin
2013-06-23 14:07 ` H. Peter Anvin
2013-06-23 19:29 ` Henrique de Moraes Holschuh
2013-06-23 20:02 ` H. Peter Anvin
2013-06-23 20:30 ` Dave Airlie
2013-06-23 20:38 ` H. Peter Anvin
2013-06-23 20:54 ` Dave Airlie
2013-06-23 20:58 ` H. Peter Anvin
2013-06-23 21:27 ` Dave Airlie
2013-06-23 21:27 ` Dave Airlie
2013-06-23 23:09 ` Andy Lutomirski
2013-06-23 21:56 ` Henrique de Moraes Holschuh
2013-06-23 22:10 ` H. Peter Anvin
2013-06-23 22:10 ` H. Peter Anvin
2013-06-24 0:02 ` Henrique de Moraes Holschuh
2013-06-24 0:31 ` H. Peter Anvin
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