From: matthieu.castet@parrot•com (Matthieu CASTET)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH v5] ARM hibernation / suspend-to-disk (fwd)
Date: Tue, 5 Jul 2011 14:37:46 +0200 [thread overview]
Message-ID: <4E13059A.4060606@parrot.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1106151349520.11405@localhost6.localdomain6>
Frank Hofmann a ?crit :
> On Mon, 13 Jun 2011, Russell King - ARM Linux wrote:
>
>> On Mon, Jun 13, 2011 at 02:20:12PM +0100, Frank Hofmann wrote:
>>>
>>> On Mon, 13 Jun 2011, Russell King - ARM Linux wrote:
>>>
>>>> On Mon, Jun 13, 2011 at 01:04:02PM +0100, Frank Hofmann wrote:
>>>>> To make it clear: IF AND ONLY IF your suspend(-to-ram) func looks like:
>>>>>
>>>>> ENTRY(acmeSoC_cpu_suspend)
>>>>> stmfd sp!, {r4-r12,lr}
>>>>> ldr r3, resume_mmu_done
>>>>> bl cpu_suspend
>>>>> resume_mmu_done:
>>>>> ldmfd sp!, {r3-r12,pc}
>>>>> ENDPROC(acmeSoC_cpu_suspend)
>>>> Nothing has that - because you can't execute that ldmfd after the call
>>>> to cpu_suspend returns. I don't think you've understood what I said on
>>>> that subject in the previous thread.
>>>>
>>> Ok, to illustrate a bit more, what is ok and what not.
>> Actually, we can do something about cpu_suspend.
>>
>> Currently cpu_suspend is not like a normal C function - when it's called
>> it returns normally to a bunch of code which is not expected to return.
>> The return path is via code pointed to by 'r3'.
>>
>> It also corrupts a bunch of registers in ways which make it non-compliant
>> with a C API.
>>
>> If we do make this complaint as a normal C-like function, it eliminates
>> this register saving. We also swap 'lr' and 'r3', so cpu_suspend
>> effectively only returns to following code on resume - and r3 points
>> to the suspend code.
>
> Hi Russell,
>
>
> this change is perfect; with this, the hibernation support code turns into
> the attached.
> That's both better and simpler to perform a full suspend/resume cycle (via
> resetting in the cpu_suspend "finisher") after the snapshot image has been
> created, instead of shoehorning a return into this.
>
>
> +static void notrace __swsusp_arch_restore_image(void)
> +{
> + extern struct pbe *restore_pblist;
> + struct pbe *pbe;
> +
> + cpu_switch_mm(swapper_pg_dir, &init_mm);
> +
> + for (pbe = restore_pblist; pbe; pbe = pbe->next)
> + copy_page(pbe->orig_address, pbe->address);
> +
One question : isn't dangerous to modify the code where we are running ?
I believe the code shouldn't change too much between the kernel that do the
resume and the resumed kernel and the copy routine should fit in the instruction
cache, but I want to be sure it doesn't cause any problem on recent arm cores
(instruction prefetching , ...)
Matthieu
next prev parent reply other threads:[~2011-07-05 12:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-13 12:04 [RFC PATCH v5] ARM hibernation / suspend-to-disk (fwd) Frank Hofmann
2011-06-13 12:26 ` Russell King - ARM Linux
2011-06-13 12:40 ` Frank Hofmann
2011-06-13 13:20 ` Frank Hofmann
2011-06-13 13:56 ` Dave Martin
2011-06-13 15:34 ` Frank Hofmann
2011-06-13 16:11 ` Frank Hofmann
2011-06-13 16:44 ` Russell King - ARM Linux
2011-06-15 13:35 ` Frank Hofmann
2011-06-16 21:31 ` Russell King - ARM Linux
2011-06-20 12:32 ` Frank Hofmann
2011-06-21 14:35 ` Russell King - ARM Linux
2011-06-29 14:52 ` Matthieu CASTET
2011-06-29 15:14 ` Frank Hofmann
2011-06-29 20:08 ` Will Deacon
2011-07-05 12:37 ` Matthieu CASTET [this message]
[not found] ` <2C577202CB5719438D4E9608C565CB2C01B69D7F@NL-EXC-07.intra.local>
2011-07-05 17:09 ` Matthieu CASTET
2011-09-30 7:48 ` Barry Song
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