From: Scott Wood <scottwood@freescale.com>
To: Trent Piepho <tpiepho@freescale.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
David Miller <davem@davemloft.net>,
linux-arch@vger.kernel.org, linuxppc-dev@ozlabs.org,
alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org
Subject: Re: MMIO and gcc re-ordering issue
Date: Tue, 27 May 2008 13:33:56 -0500 [thread overview]
Message-ID: <483C5414.6050308@freescale.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0805271043150.7453@t2.domain.actdsltmp>
Trent Piepho wrote:
> Is there an issue with anything _besides_ coherent DMA?
>
> Could one have a special version of the accessors for drivers that
> want to assume they are strictly ordered vs coherent DMA memory?
> That would be much easier to get right, without slowing _everything_
> down.
It's better to be safe by default and then optimize the fast paths than
to be relaxed by default and hang the machine in some piece of code that
runs once a month. "Premature optimization is the root of all evil",
and what not.
> One could even go as far as to allow a driver to "#define
> WANT_STRICT_IO" and then it would get the strict versions. Add that
> to any driver that uses DMA and then worry about vetting those
> drivers.
See above -- if you must have a #define, then it should be WANT_RELAXED_IO.
-Scott
WARNING: multiple messages have this Message-ID (diff)
From: Scott Wood <scottwood@freescale.com>
To: Trent Piepho <tpiepho@freescale.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org,
Linus Torvalds <torvalds@linux-foundation.org>,
David Miller <davem@davemloft.net>,
alan@lxorguk.ukuu.org.uk
Subject: Re: MMIO and gcc re-ordering issue
Date: Tue, 27 May 2008 13:33:56 -0500 [thread overview]
Message-ID: <483C5414.6050308@freescale.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0805271043150.7453@t2.domain.actdsltmp>
Trent Piepho wrote:
> Is there an issue with anything _besides_ coherent DMA?
>
> Could one have a special version of the accessors for drivers that
> want to assume they are strictly ordered vs coherent DMA memory?
> That would be much easier to get right, without slowing _everything_
> down.
It's better to be safe by default and then optimize the fast paths than
to be relaxed by default and hang the machine in some piece of code that
runs once a month. "Premature optimization is the root of all evil",
and what not.
> One could even go as far as to allow a driver to "#define
> WANT_STRICT_IO" and then it would get the strict versions. Add that
> to any driver that uses DMA and then worry about vetting those
> drivers.
See above -- if you must have a #define, then it should be WANT_RELAXED_IO.
-Scott
next prev parent reply other threads:[~2008-05-27 18:33 UTC|newest]
Thread overview: 319+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-20 20:40 [PATCH] [POWERPC] Improve (in|out)_beXX() asm code Trent Piepho
2008-05-20 20:40 ` Trent Piepho
2008-05-20 21:16 ` Benjamin Herrenschmidt
2008-05-20 21:16 ` Benjamin Herrenschmidt
2008-05-20 21:38 ` Scott Wood
2008-05-20 21:38 ` Scott Wood
2008-05-20 22:02 ` Benjamin Herrenschmidt
2008-05-20 22:02 ` Benjamin Herrenschmidt
2008-05-20 22:21 ` Trent Piepho
2008-05-20 22:15 ` Alan Cox
2008-05-20 22:15 ` Alan Cox
2008-05-20 22:35 ` Scott Wood
2008-05-20 22:35 ` Scott Wood
2008-05-20 22:39 ` David Miller
2008-05-20 22:39 ` David Miller
2008-05-20 22:43 ` Scott Wood
2008-05-20 22:43 ` Scott Wood
2008-05-20 22:53 ` David Miller
2008-05-20 22:53 ` David Miller
2008-05-23 4:24 ` Benjamin Herrenschmidt
2008-05-22 22:56 ` Trent Piepho
2008-05-22 22:56 ` Trent Piepho
2008-05-23 12:36 ` MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code) Benjamin Herrenschmidt
2008-05-23 12:36 ` Benjamin Herrenschmidt
2008-05-23 12:50 ` Benjamin Herrenschmidt
2008-05-23 12:50 ` Benjamin Herrenschmidt
2008-05-23 21:14 ` Scott Wood
2008-05-23 21:14 ` Scott Wood
2008-05-23 22:47 ` Benjamin Herrenschmidt
2008-05-23 22:47 ` Benjamin Herrenschmidt
2008-05-27 1:33 ` MMIO and gcc re-ordering issue Benjamin Herrenschmidt
2008-05-27 1:33 ` Benjamin Herrenschmidt
2008-05-27 1:40 ` David Miller
2008-05-27 1:40 ` David Miller
2008-05-27 2:15 ` Benjamin Herrenschmidt
2008-05-27 2:15 ` Benjamin Herrenschmidt
2008-05-27 2:28 ` David Miller
2008-05-27 2:28 ` David Miller
2008-05-27 3:39 ` Benjamin Herrenschmidt
2008-05-27 3:39 ` Benjamin Herrenschmidt
2008-05-27 15:35 ` Linus Torvalds
2008-05-27 15:35 ` Linus Torvalds
2008-05-27 16:47 ` Linus Torvalds
2008-05-27 16:47 ` Linus Torvalds
2008-05-27 17:31 ` Linus Torvalds
2008-05-27 17:31 ` Linus Torvalds
2008-06-02 10:36 ` Ingo Molnar
2008-06-02 10:36 ` Ingo Molnar
2008-06-02 21:53 ` Benjamin Herrenschmidt
2008-06-02 21:53 ` Benjamin Herrenschmidt
2008-05-27 21:12 ` Benjamin Herrenschmidt
2008-05-27 21:12 ` Benjamin Herrenschmidt
2008-05-27 18:23 ` Trent Piepho
2008-05-27 18:23 ` Trent Piepho
2008-05-27 18:33 ` Scott Wood [this message]
2008-05-27 18:33 ` Scott Wood
2008-05-27 21:10 ` Benjamin Herrenschmidt
2008-05-27 21:10 ` Benjamin Herrenschmidt
2008-05-27 21:30 ` Linus Torvalds
2008-05-27 21:30 ` Linus Torvalds
2008-05-27 21:38 ` Alan Cox
2008-05-27 21:38 ` Alan Cox
2008-05-27 21:53 ` Matthew Wilcox
2008-05-27 21:53 ` Matthew Wilcox
2008-05-27 21:46 ` Alan Cox
2008-05-27 21:46 ` Alan Cox
2008-05-27 22:02 ` Linus Torvalds
2008-05-27 22:02 ` Linus Torvalds
2008-05-27 21:59 ` Linus Torvalds
2008-05-27 21:59 ` Linus Torvalds
2008-05-27 21:38 ` Benjamin Herrenschmidt
2008-05-27 21:38 ` Benjamin Herrenschmidt
2008-05-27 21:42 ` Matthew Wilcox
2008-05-27 21:42 ` Matthew Wilcox
2008-05-27 22:17 ` Benjamin Herrenschmidt
2008-05-27 22:17 ` Benjamin Herrenschmidt
2008-05-28 8:36 ` Haavard Skinnemoen
2008-05-28 8:36 ` Haavard Skinnemoen
2008-05-29 11:05 ` Pantelis Antoniou
2008-05-29 11:05 ` Pantelis Antoniou
2008-05-30 1:13 ` Benjamin Herrenschmidt
2008-05-30 1:13 ` Benjamin Herrenschmidt
2008-05-30 6:07 ` Haavard Skinnemoen
2008-05-30 6:07 ` Haavard Skinnemoen
2008-05-30 7:24 ` Benjamin Herrenschmidt
2008-05-30 7:24 ` Benjamin Herrenschmidt
2008-05-30 8:27 ` Haavard Skinnemoen
2008-05-30 8:27 ` Haavard Skinnemoen
2008-05-30 9:22 ` Geert Uytterhoeven
2008-05-30 9:22 ` Geert Uytterhoeven
2008-06-02 8:11 ` Haavard Skinnemoen
2008-06-02 8:11 ` Haavard Skinnemoen
2008-06-02 15:48 ` Scott Wood
2008-06-02 15:48 ` Scott Wood
2008-06-03 7:46 ` Haavard Skinnemoen
2008-06-03 7:46 ` Haavard Skinnemoen
2008-06-04 15:31 ` Linus Torvalds
2008-06-04 15:31 ` Linus Torvalds
2008-05-27 21:55 ` Linus Torvalds
2008-05-27 21:55 ` Linus Torvalds
2008-05-27 22:19 ` Benjamin Herrenschmidt
2008-05-27 22:19 ` Benjamin Herrenschmidt
2008-05-29 7:10 ` Arnd Bergmann
2008-05-29 7:10 ` Arnd Bergmann
2008-05-29 10:46 ` Alan Cox
2008-05-29 10:46 ` Alan Cox
2008-06-02 7:24 ` Russell King
2008-06-02 7:24 ` Russell King
2008-06-03 4:16 ` Nick Piggin
2008-06-03 4:16 ` Nick Piggin
2008-06-03 4:32 ` Benjamin Herrenschmidt
2008-06-03 4:32 ` Benjamin Herrenschmidt
2008-06-03 6:11 ` Nick Piggin
2008-06-03 6:11 ` Nick Piggin
2008-06-03 6:48 ` Benjamin Herrenschmidt
2008-06-03 6:48 ` Benjamin Herrenschmidt
2008-06-03 6:53 ` Paul Mackerras
2008-06-03 6:53 ` Paul Mackerras
2008-06-03 7:18 ` Nick Piggin
2008-06-03 7:18 ` Nick Piggin
2008-06-03 14:47 ` Linus Torvalds
2008-06-03 14:47 ` Linus Torvalds
2008-06-03 18:47 ` Trent Piepho
2008-06-03 18:47 ` Trent Piepho
2008-06-03 18:55 ` Matthew Wilcox
2008-06-03 18:55 ` Matthew Wilcox
2008-06-03 19:57 ` Trent Piepho
2008-06-03 19:57 ` Trent Piepho
2008-06-03 21:35 ` Matthew Wilcox
2008-06-03 21:35 ` Matthew Wilcox
2008-06-03 21:58 ` Trent Piepho
2008-06-03 21:58 ` Trent Piepho
2008-06-04 2:00 ` Nick Piggin
2008-06-04 2:00 ` Nick Piggin
2008-06-03 19:07 ` Linus Torvalds
2008-06-03 19:07 ` Linus Torvalds
2008-06-04 2:05 ` Nick Piggin
2008-06-04 2:05 ` Nick Piggin
2008-06-04 2:46 ` Linus Torvalds
2008-06-04 2:46 ` Linus Torvalds
2008-06-04 11:47 ` Alan Cox
2008-06-04 11:47 ` Alan Cox
2008-06-10 6:56 ` Nick Piggin
2008-06-10 6:56 ` Nick Piggin
2008-06-10 17:41 ` Jesse Barnes
2008-06-10 17:41 ` Jesse Barnes
2008-06-10 18:10 ` James Bottomley
2008-06-10 18:10 ` James Bottomley
2008-06-10 19:05 ` Roland Dreier
2008-06-10 19:05 ` Roland Dreier
2008-06-10 19:19 ` Jesse Barnes
2008-06-10 19:19 ` Jesse Barnes
2008-06-11 3:29 ` Nick Piggin
2008-06-11 3:29 ` Nick Piggin
2008-06-11 3:29 ` Nick Piggin
2008-06-11 3:29 ` Nick Piggin
2008-06-11 3:40 ` Benjamin Herrenschmidt
2008-06-11 3:40 ` Benjamin Herrenschmidt
2008-06-11 4:06 ` Nick Piggin
2008-06-11 4:06 ` Nick Piggin
2008-06-11 16:07 ` Jesse Barnes
2008-06-11 16:07 ` Jesse Barnes
2008-06-12 11:27 ` Nick Piggin
2008-06-12 11:27 ` Nick Piggin
2008-06-11 4:18 ` Paul Mackerras
2008-06-11 4:18 ` Paul Mackerras
2008-06-11 5:00 ` Nick Piggin
2008-06-11 5:00 ` Nick Piggin
2008-06-11 5:13 ` Paul Mackerras
2008-06-11 5:13 ` Paul Mackerras
2008-06-11 5:35 ` Nick Piggin
2008-06-11 5:35 ` Nick Piggin
2008-06-11 6:02 ` Nick Piggin
2008-06-11 6:02 ` Nick Piggin
2008-06-12 12:14 ` Paul Mackerras
2008-06-12 12:14 ` Paul Mackerras
2008-06-12 13:08 ` Nick Piggin
2008-06-12 13:08 ` Nick Piggin
2008-06-11 14:46 ` Linus Torvalds
2008-06-11 14:46 ` Linus Torvalds
2008-06-11 5:20 ` Paul Mackerras
2008-06-11 5:20 ` Paul Mackerras
2008-06-04 2:19 ` Nick Piggin
2008-06-04 2:19 ` Nick Piggin
2008-06-03 19:43 ` Trent Piepho
2008-06-03 19:43 ` Trent Piepho
2008-06-03 21:33 ` Matthew Wilcox
2008-06-03 21:33 ` Matthew Wilcox
2008-06-03 21:44 ` Trent Piepho
2008-06-03 21:44 ` Trent Piepho
2008-06-04 2:25 ` Nick Piggin
2008-06-04 2:25 ` Nick Piggin
2008-06-04 6:39 ` Trent Piepho
2008-06-04 6:39 ` Trent Piepho
2008-06-03 22:26 ` Benjamin Herrenschmidt
2008-06-03 22:26 ` Benjamin Herrenschmidt
2008-05-27 3:42 ` Arjan van de Ven
2008-05-27 3:42 ` Arjan van de Ven
2008-05-27 4:08 ` Roland Dreier
2008-05-27 4:08 ` Roland Dreier
2008-05-27 4:20 ` Arjan van de Ven
2008-05-27 4:20 ` Arjan van de Ven
2008-05-27 7:08 ` Benjamin Herrenschmidt
2008-05-27 7:08 ` Benjamin Herrenschmidt
2008-05-27 15:50 ` Roland Dreier
2008-05-27 15:50 ` Roland Dreier
2008-05-27 16:37 ` James Bottomley
2008-05-27 16:37 ` James Bottomley
2008-05-27 17:38 ` Roland Dreier
2008-05-27 17:38 ` Roland Dreier
2008-05-27 17:53 ` James Bottomley
2008-05-27 17:53 ` James Bottomley
2008-05-27 18:07 ` Roland Dreier
2008-05-27 18:07 ` Roland Dreier
2008-05-27 18:17 ` Roland Dreier
2008-05-27 18:17 ` Roland Dreier
2008-05-27 21:23 ` Chris Friesen
2008-05-27 21:23 ` Chris Friesen
2008-05-27 21:29 ` Roland Dreier
2008-05-27 21:29 ` Roland Dreier
2008-05-27 23:04 ` Paul Mackerras
2008-05-27 23:04 ` Paul Mackerras
2008-05-27 21:11 ` Benjamin Herrenschmidt
2008-05-27 21:11 ` Benjamin Herrenschmidt
2008-05-27 21:33 ` Roland Dreier
2008-05-27 21:33 ` Roland Dreier
2008-05-27 22:13 ` Benjamin Herrenschmidt
2008-05-27 22:13 ` Benjamin Herrenschmidt
2008-05-27 22:39 ` Roland Dreier
2008-05-27 22:39 ` Roland Dreier
2008-05-29 14:47 ` Jes Sorensen
2008-05-29 14:47 ` Jes Sorensen
2008-05-29 15:01 ` James Bottomley
2008-05-29 15:01 ` James Bottomley
2008-05-30 9:36 ` Jes Sorensen
2008-05-30 9:36 ` Jes Sorensen
2008-05-30 17:21 ` Jesse Barnes
2008-05-30 17:21 ` Jesse Barnes
2008-05-31 7:57 ` Jeremy Higdon
2008-05-31 7:57 ` Jeremy Higdon
2008-05-29 21:40 ` Benjamin Herrenschmidt
2008-05-29 21:40 ` Benjamin Herrenschmidt
2008-05-29 21:48 ` Trent Piepho
2008-05-29 21:48 ` Trent Piepho
2008-05-29 22:05 ` Benjamin Herrenschmidt
2008-05-29 22:05 ` Benjamin Herrenschmidt
2008-05-30 1:53 ` Trent Piepho
2008-05-30 1:53 ` Trent Piepho
2008-05-29 21:53 ` Jesse Barnes
2008-05-29 21:53 ` Jesse Barnes
2008-05-30 9:39 ` Jes Sorensen
2008-05-30 9:39 ` Jes Sorensen
2008-05-30 9:48 ` Jes Sorensen
2008-05-30 9:48 ` Jes Sorensen
2008-05-31 8:14 ` Pavel Machek
2008-05-31 8:14 ` Pavel Machek
2008-06-02 9:48 ` Jes Sorensen
2008-06-02 9:48 ` Jes Sorensen
2008-05-29 22:06 ` Roland Dreier
2008-05-29 22:06 ` Roland Dreier
2008-05-29 22:25 ` Trent Piepho
2008-05-29 22:25 ` Trent Piepho
2008-05-30 3:56 ` Paul Mackerras
2008-05-30 3:56 ` Paul Mackerras
2008-05-31 7:52 ` Jeremy Higdon
2008-05-31 7:52 ` Jeremy Higdon
2008-06-02 9:56 ` Jes Sorensen
2008-06-02 9:56 ` Jes Sorensen
2008-06-02 21:02 ` Jeremy Higdon
2008-06-02 21:02 ` Jeremy Higdon
2008-06-03 4:33 ` Nick Piggin
2008-06-03 4:33 ` Nick Piggin
2008-06-03 8:15 ` Jeremy Higdon
2008-06-03 8:15 ` Jeremy Higdon
2008-06-03 8:19 ` Nick Piggin
2008-06-03 8:19 ` Nick Piggin
2008-06-03 8:45 ` Jeremy Higdon
2008-06-03 8:45 ` Jeremy Higdon
2008-06-03 16:52 ` Jesse Barnes
2008-06-03 16:52 ` Jesse Barnes
2008-06-05 8:40 ` Jes Sorensen
2008-06-05 8:40 ` Jes Sorensen
2008-06-05 8:43 ` Benjamin Herrenschmidt
2008-06-05 8:43 ` Benjamin Herrenschmidt
2008-06-12 15:07 ` Matthew Wilcox
2008-06-12 15:07 ` Matthew Wilcox
2008-06-13 0:07 ` Benjamin Herrenschmidt
2008-06-13 0:07 ` Benjamin Herrenschmidt
2008-05-31 8:04 ` Pavel Machek
2008-05-31 8:04 ` Pavel Machek
2008-05-27 8:24 ` Alan Cox
2008-05-27 8:24 ` Alan Cox
2008-05-27 15:28 ` Jonathan Corbet
2008-05-27 15:28 ` Jonathan Corbet
2008-05-20 22:55 ` [PATCH] [POWERPC] Improve (in|out)_beXX() asm code Trent Piepho
2008-05-20 22:55 ` Trent Piepho
2008-05-21 14:01 ` Benjamin Herrenschmidt
2008-05-21 14:01 ` Benjamin Herrenschmidt
2008-05-20 22:00 ` Trent Piepho
2008-05-20 22:00 ` Trent Piepho
2008-05-21 14:00 ` Benjamin Herrenschmidt
2008-05-21 14:00 ` Benjamin Herrenschmidt
2008-05-21 19:44 ` Trent Piepho
2008-05-21 19:44 ` Trent Piepho
2008-05-21 20:41 ` Benjamin Herrenschmidt
2008-05-21 20:41 ` Benjamin Herrenschmidt
2008-05-20 22:00 ` Andreas Schwab
2008-05-20 22:00 ` Andreas Schwab
2008-05-20 22:11 ` Trent Piepho
2008-05-20 22:11 ` Trent Piepho
2008-05-20 22:47 ` Andreas Schwab
2008-05-20 22:47 ` Andreas Schwab
2008-05-20 23:14 ` Trent Piepho
2008-05-20 23:14 ` Trent Piepho
2008-05-21 8:03 ` Andreas Schwab
2008-05-21 8:03 ` Andreas Schwab
2008-05-21 20:25 ` Trent Piepho
2008-05-21 20:25 ` Trent Piepho
2008-05-27 23:48 ` [PATCH V2] [POWERPC] Improve (in|out)_[bl]eXX() " Trent Piepho
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