From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: Problem with dma_alloc_coherent at linux-2.6.33-arm1 , with RealView platform,board PBX-A9 and armv7 instructions.
Date: Thu, 15 Jul 2010 10:38:31 +0100 [thread overview]
Message-ID: <20100715093831.GE26212@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20100715093107.GB17605@trinity.fluff.org>
On Thu, Jul 15, 2010 at 10:31:07AM +0100, Ben Dooks wrote:
> On Thu, Jul 15, 2010 at 05:13:57PM +0800, David Yang wrote:
> > I don't know the reason until now.I guess the memory allocated by the
> > dma_alloc_coherent may be cached....if not , why it is so slowly?
>
> The dma_alloc_coherent coherent should return uncachable and un-bufferable
> memory, otherwise you meed explicit flushing commands when changing between
> the HW and CPU ownership.
It's a result of the weakly ordered memory model - writes to memory
are now delayed and can be re-ordered, but not across the appropriate
barrier instructions.
Lack of barrier instructions makes that these writes can arrive in
unexpected orders, which will cause exactly these kinds of problems.
Catalin has been tracking down where these barriers need to be added,
so we're getting these issues solved - but we can only find them
through people using the kernel, reporting problems like this, and
fixing the missing places.
next prev parent reply other threads:[~2010-07-15 9:38 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-15 9:13 Problem with dma_alloc_coherent at linux-2.6.33-arm1 , with RealView platform,board PBX-A9 and armv7 instructions David Yang
2010-07-15 9:31 ` Ben Dooks
2010-07-15 9:38 ` Russell King - ARM Linux [this message]
2010-07-15 9:56 ` David Yang
2010-07-15 9:59 ` Russell King - ARM Linux
2010-07-15 10:06 ` David Yang
2010-07-15 10:04 ` Shilimkar, Santosh
2010-07-15 10:09 ` Russell King - ARM Linux
2010-07-15 11:16 ` David Yang
2010-07-15 11:28 ` Russell King - ARM Linux
2010-07-15 12:15 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , withRealView " Catalin Marinas
2010-07-15 9:40 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , with RealView " David Yang
2010-07-15 12:19 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , withRealView " Catalin Marinas
2010-07-15 9:35 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , with RealView " Russell King - ARM Linux
2010-07-15 12:21 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , withRealView " Catalin Marinas
2010-07-15 12:52 ` David Yang
2010-07-15 12:56 ` Catalin Marinas
2010-07-15 13:10 ` David Yang
2010-07-15 13:17 ` Catalin Marinas
2010-07-17 7:05 ` David Yang
2010-07-19 12:29 ` Catalin Marinas
2010-07-20 3:17 ` David Yang
2010-07-20 8:53 ` Catalin Marinas
2010-07-20 9:22 ` David Yang
2010-07-20 9:26 ` Catalin Marinas
2010-07-15 12:25 ` Problem with dma_alloc_coherent at linux-2.6.33-arm1 , with RealView " Catalin Marinas
2010-07-15 12:57 ` David Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20100715093831.GE26212@n2100.arm.linux.org.uk \
--to=linux@arm.linux.org.uk \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).