From: Jeff Garzik <jeff@garzik.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Russell King <rmk@arm.linux.org.uk>, linux-ide@vger.kernel.org
Subject: Re: 2.6.32: Promise UDMA33 card refuses to work in UDMA mode
Date: Mon, 04 Jan 2010 10:32:55 -0500 [thread overview]
Message-ID: <4B420A27.9060407@garzik.org> (raw)
In-Reply-To: <20100104151637.559c4780@lxorguk.ukuu.org.uk>
On 01/04/2010 10:16 AM, Alan Cox wrote:
>> If the drive immediately starts the UDMA protocol after a write to the
>> command register (as it probably will for the DMA WRITE command), then
>> we'll be accessing the taskfile in the middle of the UDMA setup, which
>> can't be good. It's certainly a violation of the ATA specs.
>
> I concur entirely - that wants pushing into the upstream kernel ASAP and
> if its ok backporting. May also be worth seeing if that fixes the funny
> in the ALi setup.
How do you think one tests for command completion? :) There does not
seem to be a general problem reading AltStatus(BSY) during a DMA
transfer. IDE driver and other well known codebases have been doing
that for decades.
I think the undefined behavior is only where the AltStatus read occurs
before the 400ns period specified by ATA... excising the AltStatus read
there (ata_sff_pause) should be fine for PIO, but problematic for MMIO
chipsets that need posted writes flushed prior to the 400ns delay.
Jeff
next prev parent reply other threads:[~2010-01-04 15:33 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-24 18:13 2.6.32: Promise UDMA33 card refuses to work in UDMA mode Russell King
2009-12-24 21:54 ` Russell King
2010-01-03 0:23 ` Russell King
2010-01-03 3:08 ` Robert Hancock
2010-01-03 10:05 ` Russell King
2010-01-03 11:40 ` Alan Cox
2010-01-03 22:35 ` [PATCH] Fix Promise UDMA33 IDE driver (pdc202xx_old) Russell King
2010-01-04 19:14 ` Sergei Shtylyov
2010-01-05 6:26 ` David Miller
2010-01-05 17:49 ` Russell King
2010-01-05 17:52 ` Sergei Shtylyov
2010-01-03 23:46 ` 2.6.32: Promise UDMA33 card refuses to work in UDMA mode Russell King
2010-01-04 10:37 ` Alan Cox
2010-01-04 13:30 ` Russell King
2010-01-04 15:16 ` Alan Cox
2010-01-04 15:32 ` Jeff Garzik [this message]
2010-01-04 15:44 ` Russell King
2010-01-04 15:55 ` Alan Cox
2010-01-04 16:15 ` Russell King
2010-01-04 16:48 ` Jeff Garzik
2010-01-04 17:16 ` Sergei Shtylyov
2010-01-04 15:48 ` Alan Cox
2010-01-04 15:25 ` Jeff Garzik
2010-01-04 15:42 ` Russell King
2010-01-05 2:06 ` Robert Hancock
2010-01-05 11:25 ` Alan Cox
2010-01-05 13:00 ` Jeff Garzik
2010-01-05 13:37 ` Alan Cox
2010-01-05 13:11 ` Jeff Garzik
2010-01-04 15:46 ` Alan Cox
2010-01-04 16:32 ` Jeff Garzik
2010-01-04 17:02 ` Alan Cox
2010-01-04 17:27 ` Jeff Garzik
2010-01-04 17:30 ` Russell King
2010-01-04 18:03 ` Jeff Garzik
2010-01-04 18:06 ` Russell King
2010-01-04 18:35 ` Jeff Garzik
2010-01-04 17:38 ` Alan Cox
2010-01-04 18:07 ` Jeff Garzik
2010-01-04 18:29 ` Jeff Garzik
2010-01-04 16:31 ` Bartlomiej Zolnierkiewicz
2010-01-04 17:28 ` Russell King
2010-01-04 17:39 ` Alan Cox
2010-01-04 17:46 ` Russell King
2010-01-04 18:20 ` Alan Cox
2010-01-04 17:49 ` Bartlomiej Zolnierkiewicz
2010-01-05 1:03 ` Robert Hancock
2010-01-05 10:04 ` Jeff Garzik
2010-01-05 17:44 ` Russell King
2010-01-06 0:30 ` Robert Hancock
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