From: robherring2@gmail•com (Rob Herring)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: decompressor: clear SCTLR.A bit for v7 cores
Date: Thu, 11 Oct 2012 07:43:22 -0500 [thread overview]
Message-ID: <1349959402-24164-1-git-send-email-robherring2@gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1210100939160.16518@xanadu.home>
From: Rob Herring <rob.herring@calxeda•com>
With recent compilers and move to generic unaligned.h in commit d25c881
(ARM: 7493/1: use generic unaligned.h), unaligned accesses will be used
by the LZO decompressor on v7 cores. So we need to make sure unaligned
accesses are allowed by clearing the SCTLR A bit.
While v6 can support unaligned accesses, it is optional and current
compilers won't emit unaligned accesses. So we don't clear the A bit for
v6.
Signed-off-by: Rob Herring <rob.herring@calxeda•com>
Acked-by: Nicolas Pitre <nico@linaro•org>
Tested-by: Shawn Guo <shawn.guo@linaro•org>
---
The contents of this were already reviewed on this thread, so I sent this
to the patch system and this was Russell's reply:
> NAK for two reasons.
>
> 1. It hasn't been on the list (I can't find a match for "clear SCTLR.A"
> in my mailbox)
>
> 2. The behaviour of unaligned accesses vary depending on CPU. Some
> fix-up the access, others load the word and then rotate it. If we have
> decompressors which perform unaligned accesses, we need to fix this
> properly to avoid the CPU specific behaviour, rather than tweaking
> control bits to hide the problem.
I'm simply matching the behavior of the kernel itself. The A bit is cleared
for v7 kernels and compilers only generate unaligned accesses for v7.
Without this the initial state of the A bit is undefined as a bootloader
could have cleared it already. We should document the required state or set
it to what we want.
Rob
arch/arm/boot/compressed/head.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index bc67cbf..b2e30b8 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -654,6 +654,7 @@ __armv7_mmu_cache_on:
#endif
mrc p15, 0, r0, c1, c0, 0 @ read control reg
bic r0, r0, #1 << 28 @ clear SCTLR.TRE
+ bic r0, r0, #1 << 1 @ clear SCTLR.A
orr r0, r0, #0x5000 @ I-cache enable, RR cache replacement
orr r0, r0, #0x003c @ write buffer
#ifdef CONFIG_MMU
--
1.7.9.5
next prev parent reply other threads:[~2012-10-11 12:43 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 ` Rob Herring [this message]
2012-10-11 13:09 ` [PATCH] ARM: decompressor: clear SCTLR.A bit for v7 cores 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
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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