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From: nicolas.pitre@linaro.org (Nicolas Pitre)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: decompressor: clear SCTLR.A bit for v7 cores
Date: Thu, 11 Oct 2012 11:58:15 -0400 (EDT)	[thread overview]
Message-ID: <alpine.LFD.2.02.1210111152580.16518@xanadu.home> (raw)
In-Reply-To: <20121011135925.GR4625@n2100.arm.linux.org.uk>

On Thu, 11 Oct 2012, Russell King - ARM Linux wrote:

> On Thu, Oct 11, 2012 at 08:31:47AM -0500, Rob Herring wrote:
> > This only affects v7 cores. It should not vary for v7 cores as unaligned
> > access is a required feature. So how is it going to vary on v7 CPUs?
> > We've got bigger problems if there are v7 cores that don't handle
> > unaligned accesses.
> 
> Oh, and this gives me a third reason to NAK this patch.  Why only ensure
> that the A bit is clear for v7 CPUs?  Why not v6, v5, v4 too?  Why does
> ARMv7 get this special treatment?

As I said, gcc knows that ARMv7 can perform word sized accesses even 
with misaligned pointers.  So when it is passed a pointer marked with 
the packed attribute, it will generate a series of byte accesses when 
compiling for anything but ARMv7, and use a single ldr or str when 
compiling for ARMv7.


Nicolas

  reply	other threads:[~2012-10-11 15:58 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-05  1:23 [PATCH v2 0/5] Use more asm-generic headers Rob Herring
2012-08-05  1:23 ` [PATCH v2 1/5] ARM: use generic version of identical asm headers Rob Herring
2012-08-05  1:23 ` [PATCH v2 2/5] ARM: add strstr declaration for decompressors Rob Herring
2012-08-05  1:23 ` [PATCH v2 3/5] ARM: use generic unaligned.h Rob Herring
2012-10-08 16:43   ` Shawn Guo
2012-10-08 20:34     ` Rob Herring
2012-10-08 23:28       ` Shawn Guo
2012-10-09  2:27         ` Rob Herring
2012-10-09  2:45           ` Shawn Guo
2012-10-09  4:01           ` Nicolas Pitre
2012-10-10 13:29             ` Rob Herring
2012-10-10 13:57               ` Nicolas Pitre
2012-10-11 12:43                 ` [PATCH] ARM: decompressor: clear SCTLR.A bit for v7 cores Rob Herring
2012-10-11 13:09                   ` Russell King - ARM Linux
2012-10-11 13:31                     ` Rob Herring
2012-10-11 13:41                       ` Russell King - ARM Linux
2012-10-11 15:44                         ` Nicolas Pitre
2012-10-23 20:32                           ` Gregory CLEMENT
2012-10-25 12:07                             ` Russell King - ARM Linux
2012-10-11 13:59                       ` Russell King - ARM Linux
2012-10-11 15:58                         ` Nicolas Pitre [this message]
2012-10-25  9:34                   ` Johannes Stezenbach
2012-10-25 12:41                     ` Rob Herring
2012-10-25 13:30                       ` Arnd Bergmann
2012-10-25 14:16                       ` Johannes Stezenbach
2012-10-25 14:25                         ` Rob Herring
2012-10-25 15:02                           ` Nicolas Pitre
2012-10-25 15:08                           ` Johannes Stezenbach
2012-11-05 10:48                             ` Dave Martin
2012-11-05 11:13                               ` Russell King - ARM Linux
2012-11-05 13:02                                 ` Dave Martin
2012-11-05 13:43                                   ` Johannes Stezenbach
2012-11-05 15:39                                   ` Russell King - ARM Linux
2012-11-05 16:13                                     ` Nicolas Pitre
2012-11-05 17:26                                       ` Dave Martin
2012-11-05 17:44                                         ` Rob Herring
2012-11-05 20:02                                           ` Nicolas Pitre
2012-11-05 17:46                                         ` Nicolas Pitre
2012-11-05 13:48                                 ` Rob Herring
2012-11-05 22:02                                   ` Michael Hope
2013-02-20 14:56                                     ` Johannes Stezenbach
2013-02-20 15:07                                       ` Johannes Stezenbach
2012-08-05  1:23 ` [PATCH v2 4/5] ARM: use generic termios.h Rob Herring
2012-08-05  1:24 ` [PATCH v2 5/5] ARM: convert asm/irqflags.h to use asm-generic/irqflags.h Rob Herring
2012-08-05  9:34 ` [PATCH v2 0/5] Use more asm-generic headers Thomas Petazzoni
2012-08-06 14:35 ` Arnd Bergmann

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