From: Ralf Baechle <ralf@linux-mips.org>
To: Imran Badr <imran.badr@cavium.com>
Cc: "'Alan Cox'" <alan@lxorguk.ukuu.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: Cache coherency and snooping
Date: Wed, 14 Aug 2002 10:16:54 +0200 [thread overview]
Message-ID: <20020814101654.B14197@linux-mips.org> (raw)
In-Reply-To: <0aa401c2432e$04a95cc0$9e10a8c0@IMRANPC>; from imran.badr@cavium.com on Tue, Aug 13, 2002 at 06:00:43PM -0700
On Tue, Aug 13, 2002 at 06:00:43PM -0700, Imran Badr wrote:
> Please advise if following sequence of operations are going to help:
>
> alloc memory
> reserve the page
> flush every cache
That's an extremly expensive operation on some platforms and there's no
portable kernel API to do it.
Note that the flush_cache_*() functions are not suitable for I/O as you
want to do it. Many platforms such as i386 implement these functions
as empty functions.
> call ioremap_nocache
You said you intend to remap memory, that is RAM. The ioremap*() functions
will refuse to remap RAM; they're only suitable for other types of memory
such as PCI boards. If the latter was your intension then ioremap_nocache()
will work as intended.
Again, unless your hardware is fucked beyond recognition it'll do a better
job at keeping cache coherence than software.
Ralf
next prev parent reply other threads:[~2002-08-14 8:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-13 22:57 patch 04/38: SUNRPC: support for GSSD client Kendrick M. Smith
2002-08-13 23:22 ` Cache coherency and snooping Imran Badr
2002-08-13 23:38 ` Alan Cox
2002-08-14 0:08 ` Ralf Baechle
2002-08-14 0:19 ` Imran Badr
2002-08-14 0:29 ` Ralf Baechle
2002-08-14 1:00 ` Imran Badr
2002-08-14 1:38 ` Rik van Riel
2002-08-14 1:56 ` Imran Badr
2002-08-14 8:16 ` Ralf Baechle [this message]
2002-08-14 9:00 ` David S. Miller
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