From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Max T. Woodbury" <max.teneyck.woodbury@verizon.net>
Cc: "Eric D. Mudama" <edmudama@bounceswoosh.org>, linux-ide@vger.kernel.org
Subject: Re: ide-io.c, ide_do_request -- race condition?
Date: Fri, 16 Jul 2004 13:45:20 -0400 [thread overview]
Message-ID: <1089999920.1865.82.camel@gaston> (raw)
In-Reply-To: <40F72B6A.6F12F454@verizon.net>
> Huh? Unless something major has changed since the last time I looked at
> DMA hardware (and it has been a few years), DMA uses the same transfer
> sequence from the devices point of view as PIO. The fact that the
> transfer is under the control of another device rather than a program
> should be transparent to the target device. Impedance mismatches,
> reflections and constructive and destructive interference caused by
> cable problems don't care about who's in control of the busses.
>
> I can see a possible problem with cache consistency causing problems
> with PIO, but there are similar (abet in some sense inverted or
> reversed) problems with DMA.
Actually, it's not the same transfer sequence (and it's not the same
ATA commands neither). Look for an ATA spec and check out the signals
on the wire, DMA is different at the device level as well.
In addition, U/DMA does CRC
Ben.
next prev parent reply other threads:[~2004-07-16 17:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-12 17:52 ide-io.c, ide_do_request -- race condition? Max T. Woodbury
2004-07-12 18:35 ` Eric D. Mudama
2004-07-16 6:12 ` Max T. Woodbury
2004-07-16 7:02 ` Jens Axboe
2004-07-16 16:33 ` Max T. Woodbury
2004-07-16 17:57 ` Jens Axboe
2004-07-16 7:06 ` Jeff Garzik
2004-07-16 17:45 ` Benjamin Herrenschmidt [this message]
-- strict thread matches above, loose matches on Subject: below --
2004-07-11 14:38 Max T. Woodbury
2004-07-05 22:51 Max T. Woodbury
2004-07-07 19:43 ` Bartlomiej Zolnierkiewicz
2004-07-10 19:25 ` Max T. Woodbury
2004-07-10 20:07 ` Bartlomiej Zolnierkiewicz
2004-07-11 15:02 ` Max T. Woodbury
2004-07-12 15:15 ` Max T. Woodbury
2004-07-12 15:47 ` Bartlomiej Zolnierkiewicz
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=1089999920.1865.82.camel@gaston \
--to=benh@kernel.crashing.org \
--cc=edmudama@bounceswoosh.org \
--cc=linux-ide@vger.kernel.org \
--cc=max.teneyck.woodbury@verizon.net \
/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).