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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	"Ingo Molnar" <mingo@elte.hu>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Björn Steinbrink" <B.Steinbrink@gmx.de>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.24-git: kmap_atomic() WARN_ON()
Date: Wed, 27 Feb 2008 00:02:22 +0000	[thread overview]
Message-ID: <20080227000222.158f9220@core> (raw)
In-Reply-To: <47C499CF.2000605@pobox.com>

> Aside: The "FIXME: use bounce buffer" comment above indicates the more 
> optimal PIO data xfer approach of
> 
> 	local_irq_save()
> 	kmap_atomic()
> 	memcpy into bounce buffer
> 	kunmap_atomic()
> 	local_irq_restore()
> 
> 	/* do slow PIO bitbanging data transfer */
> 	ap->ops->data_xfer(...)

Definitely - older PATA controllers are unbuffered. A PIO_0 transfer is
running at ISA speed with IRQs off. Guaranteed to give Ingo's RT a blip.

Alan

  reply	other threads:[~2008-02-27  0:15 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-06 23:58 Thomas Gleixner
2008-02-13 22:39 ` Rafael J. Wysocki
2008-02-14  1:13   ` Thomas Gleixner
2008-02-25 19:59 ` Björn Steinbrink
2008-02-25 20:08   ` Jeff Garzik
2008-02-25 20:35     ` Björn Steinbrink
2008-02-25 20:40     ` Andrew Morton
2008-02-25 22:01       ` Thomas Gleixner
2008-02-25 22:17         ` Andrew Morton
2008-02-25 23:19         ` Jeff Garzik
2008-02-26  8:39           ` Ingo Molnar
2008-02-26 16:32             ` Jeff Garzik
2008-02-26 18:19               ` Andrew Morton
2008-02-26 20:49                 ` Ingo Molnar
2008-02-26 21:37                   ` Andrew Morton
2008-02-26 22:59                     ` Jeff Garzik
2008-02-27  0:02                       ` Alan Cox [this message]
2008-02-26 23:49                   ` Nick Piggin
2008-02-26  8:50           ` Thomas Gleixner

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