From: Eugene Surovegin <ebs@ebshome.net>
To: Matt Porter <mporter@kernel.crashing.org>
Cc: Bret Indrelee <Bret.Indrelee@qlogic.com>,
Roland Dreier <roland@topspin.com>,
Matt Porter <mporter@kernel.crashing.org>,
Linux PPC Embedded mailing list
<linuxppc-embedded@lists.linuxppc.org>
Subject: Re: Any restrictions on DMA address boundry?
Date: Thu, 25 Sep 2003 13:25:00 -0700 [thread overview]
Message-ID: <5.1.0.14.2.20030925131735.03abfab8@mail.ebshome.net> (raw)
In-Reply-To: <20030925125653.A16002@home.com>
At 12:56 PM 9/25/2003, Matt Porter wrote:
>When a buffer is allocated using the allowed methods (as defined in
>DMA-mapping.txt) to obtain memory for use in DMA, there is
>no guarantee that the buffer is cacheline aligned.
Hmm, I don't think this is true.
DMA-mapping.txt explicitly states that pci_alloc_consistent() returns
aligned memory buffer:
" ... The cpu return address and the DMA bus master address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size. This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary..."
I think it's safe to assume that PAGE_SIZE alignment also guarantees
cacheline alignment for all existing CPUs.
Eugene.
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2003-09-25 20:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-22 15:13 Any restrictions on DMA address boundry? Bret Indrelee
2003-09-22 16:59 ` Matt Porter
2003-09-25 17:56 ` Roland Dreier
2003-09-25 18:15 ` Bret Indrelee
2003-09-25 18:26 ` Roland Dreier
2003-09-25 20:54 ` Eugene Surovegin
2003-09-25 19:56 ` Matt Porter
2003-09-25 20:20 ` Bret Indrelee
2003-09-25 20:55 ` Matt Porter
2003-09-25 21:27 ` Bret Indrelee
2003-09-25 20:25 ` Eugene Surovegin [this message]
2003-09-25 20:32 ` Bret Indrelee
2003-09-25 20:57 ` Matt Porter
2003-09-25 20:41 ` Matt Porter
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=5.1.0.14.2.20030925131735.03abfab8@mail.ebshome.net \
--to=ebs@ebshome.net \
--cc=Bret.Indrelee@qlogic.com \
--cc=linuxppc-embedded@lists.linuxppc.org \
--cc=mporter@kernel.crashing.org \
--cc=roland@topspin.com \
/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).