[PATCH 3/4] at91 : remove wait_for_interrupt definition

[Russell King - ARM Linux]

On Wed, Jan 25, 2012 at 03:39:49PM +0100, Daniel Lezcano wrote:
> On 01/25/2012 01:18 AM, Russell King - ARM Linux wrote:
>> On Wed, Jan 25, 2012 at 12:56:07AM +0100, Daniel Lezcano wrote:
>>> All the "wait_for_interrupt" definition are aliases to cpu_do_idle.
>>> Only the rm9200 has an asm routine to switch to wfi. But the cpu_do_idle
>>> for this platform has exactly the same asm routine.
>>>
>>> arch/arm/mm/proc-arm920.S
>>> ...
>>> ENTRY(cpu_arm920_do_idle)
>>>          mcr     p15, 0, r0, c7, c0, 4           @ Wait for interrupt
>>> ...
>>>
>>> Then it is safe to invoke cpu_do_idle for this platform.
>>
>> No it is not.
>>
>> Please read Nicolas' post:
>>
>> http://lists.arm.linux.org.uk/lurker/message/20120112.144129.827ae490.en.html
>>
>> and think about what "DWB is needed before putting SDRAM into self-refresh
>> because any subsequent access to SDRAM will force it to resume from
>> self-refresh state" means.
>>
>> Consider that if you _branch_ somewhere else, you _could_ cause a cache
>> line fetch, which will have to come from SDRAM.
>
> Oh, right. I am not familiar with this part, thanks for the clarification.
>
>>  From Nicolas' post, it's pretty clear to me that the AT91RM9200 requires
>> carefully crafted assembly which can't be separated in this way to work,
>> which I mostly supplied in this mail:
>>
>> http://lists.arm.linux.org.uk/lurker/message/20120109.144443.3626e5a6.en.html
>
> Ok, this is what does the patch 4/4, it changes the self-refresh and wfi  
> into an asm routine where cpu_do_idle call is removed. Can I consider by  
> folding 3/4 and 4/4 ? So the buggy cpu_do_idle change won't appear...

So I see your patch is in arm-soc now, inspite of my note that it's
probably broken.

If it's been tested, then all the asm() stuff in arch/arm/mach-at91/pm.c
along with the sdram crap can be removed.