From: per.forlin@stericsson•com (Per Förlin)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm: proc-v7: pc phy addresses before disable MMU
Date: Fri, 30 Sep 2011 11:34:06 +0200 [thread overview]
Message-ID: <4E858D0E.3000104@stericsson.com> (raw)
In-Reply-To: <20110930083445.GA3895@e102144-lin.cambridge.arm.com>
On 09/30/2011 10:34 AM, Will Deacon wrote:
> Hi Per,
>
> On Fri, Sep 30, 2011 at 06:37:41AM +0100, Per F?rlin wrote:
>> On 09/24/2011 03:02 PM, Russell King - ARM Linux wrote:
>>> On Sat, Sep 24, 2011 at 02:55:42PM +0200, Per F?rlin wrote:
>>>> On 09/24/2011 01:00 PM, Will Deacon wrote:
>>>>> On Sat, Sep 24, 2011 at 10:32:48AM +0100, Per F?rlin wrote:
>>>>>> I am trying to figure out how I can get the value of PHYS_OFFSET in assembler code (proc-v7.S).
>>>>>> I guess I could use the value calculated in arch/arm/kernel.head.S but wouldn't that make
>>>>>> this patch dependent on CONFIG_ARM_PATCH_PHYS_VIRT?
>>>>>
>>>>> Wouldn't we just be better off passing a physical address to cpu_v7_reset
>>>>> instead?
>>>>>
>>>> Good point! I'm fine with that.
>>>
>>> Alternatively, call it using the phys address.
>> I changed the code to use a label instead of the ARM specific instruction offset +4. A few more lines but the intention is that it should work with both ARM and THUMB. I'm in favour of Russell's idea of setting pc to physical before calling cpu_reset().
>> /* Go to physical addresses to be ready for MMU disable */
>> asm("ADR r1, pc_phy_here \n\t"
>> "sub r1, %0 \n\t"
>> "mov pc, r1 \n\t"
>> "pc_phy_here: \n\t"
>> : :"r" (PAGE_OFFSET - PHYS_OFFSET) : "r1", "cc");
>
> I'm not sure why all of this is necessary. Take a look at my kexec patches
> here:
>
> http://www.linux-arm.org/git?p=linux-2.6-wd.git;a=shortlog;h=refs/heads/kexec-mmu-off
>
> The interesting bit is __arm_machine_reset in kernel/process.c
>
/* Switch to the identity mapping. */
phys_reset = (phys_reset_t)virt_to_phys(cpu_reset);
phys_reset(reset_args->reset_code_phys);
Yes this is definitely how it should be done. My mind was stuck in the assembler code.
If I get this right the bug I run into is already fixed by your kexec patches. I could simply use your patches?
Thanks,
Per
next prev parent reply other threads:[~2011-09-30 9:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-24 8:02 [PATCH] arm: proc-v7: pc phy addresses before disable MMU Per Forlin
2011-09-24 8:06 ` Russell King - ARM Linux
2011-09-24 8:13 ` Mika Westerberg
2011-09-24 9:32 ` Per Förlin
2011-09-24 11:00 ` Will Deacon
2011-09-24 12:55 ` Per Förlin
2011-09-24 13:02 ` Russell King - ARM Linux
2011-09-30 5:37 ` Per Förlin
2011-09-30 8:34 ` Will Deacon
2011-09-30 9:34 ` Per Förlin [this message]
2011-09-30 9:38 ` Will Deacon
2011-10-03 14:32 ` Dave Martin
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=4E858D0E.3000104@stericsson.com \
--to=per.forlin@stericsson$(echo .)com \
--cc=linux-arm-kernel@lists$(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