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: Mon, 05 Nov 2012 11:44:52 -0600 [thread overview]
Message-ID: <5097FB14.20404@gmail.com> (raw)
In-Reply-To: <20121105172624.GE2005@linaro.org>
On 11/05/2012 11:26 AM, Dave Martin wrote:
> On Mon, Nov 05, 2012 at 11:13:51AM -0500, Nicolas Pitre wrote:
>> On Mon, 5 Nov 2012, Russell King - ARM Linux wrote:
>>
>>> On Mon, Nov 05, 2012 at 01:02:55PM +0000, Dave Martin wrote:
>>>> Why not allow unaligned accesses in the decompressor, though, both
>>>> for v6 and v7?
>>>
>>> EXACTLY.
>>
>> I have no objections to that. In fact, I made a remark to this effect
>> in my initial review of this patch. Whether or not gcc does take
>> advantage of this hardware ability in the end is orthogonal.
>
> For the sake of argument, here's how it might look.
>
> Currently, I make no attempt to restore the original state of the U bit.
> The A bit if forced later by the kernel during boot, after a short window
> during which we should only run low-level arch code and therefore where
> no unaligned accesses should happen.
>
> Does anyone think these issues are likely to be important?
>
And here is my updated version that does v6 somewhat differently:
8<------------------------------------------------------------------
>From 76c2b7685397f13aa53f426822128430fc24b8a0 Mon Sep 17 00:00:00 2001
From: Rob Herring <rob.herring@calxeda•com>
Date: Mon, 5 Nov 2012 11:39:48 -0600
Subject: [PATCH v2] ARM: decompressor: clear SCTLR.A bit for v6 and v7 cores
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. In case this changes and to align
with the kernel behavior, we clear the A bit and set the U bit.
Signed-off-by: Rob Herring <rob.herring@calxeda•com>
Acked-by: Nicolas Pitre <nico@linaro•org>
Tested-by: Shawn Guo <shawn.guo@linaro•org>
---
arch/arm/boot/compressed/head.S | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index bc67cbf..f14d7ec 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -629,6 +629,11 @@ __armv4_mmu_cache_on:
mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
mcr p15, 0, r0, c8, c7, 0 @ flush I,D TLBs
mrc p15, 0, r0, c1, c0, 0 @ read control reg
+ mrc p15, 0, r11, c0, c0 @ get processor ID
+ and r11, r11, #0xf0000
+ tst r11, #0x70000 @ ARMv6
+ orreq r0, r0, #1 << 22 @ set SCTLR.U
+ biceq r0, r0, #1 << 1 @ clear SCTLR.A
orr r0, r0, #0x5000 @ I-cache enable, RR cache replacement
orr r0, r0, #0x0030
#ifdef CONFIG_CPU_ENDIAN_BE8
@@ -654,6 +659,7 @@ __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
--
1.7.10.4
next prev parent reply other threads:[~2012-11-05 17:44 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5097FB14.20404@gmail.com \
--to=robherring2@gmail$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox