[RFC][PATCH 0/7] OMAP4 cpuidle cleanup

Daniel Lezcano daniel.lezcano at linaro.org
Wed Mar 21 10:59:21 UTC 2012


On 03/21/2012 11:49 AM, Shilimkar, Santosh wrote:
> On Wed, Mar 21, 2012 at 4:13 PM, Daniel Lezcano
> <daniel.lezcano at linaro.org>  wrote:
>> On 03/21/2012 10:56 AM, Santosh Shilimkar wrote:
>>>
>>> On Wednesday 21 March 2012 03:21 PM, Daniel Lezcano wrote:
>>>>
>>>> On 03/21/2012 10:36 AM, Shilimkar, Santosh wrote:
>>>>>
>>>>> On Wed, Mar 21, 2012 at 2:57 PM, Daniel Lezcano
>>>>> <daniel.lezcano at linaro.org>     wrote:
>>>>>>
>>>>>> This patchset is a proposition to improve a bit the code.
>>>>>> The changes are code cleanup and does not change the behavior of the
>>>>>> driver itself.
>>>>>>
>>>>> Thanks. Will have a look at your series.
>>>>
>>>>
>>>> Cool, thanks.
>>>>
>>>>>> A couple a things call my intention. Why the cpuidle device is set
>>>>>> for cpu0 only
>>>>>
>>>>> Because the mainline code CPUIDLE is supported along with CPUhotplug.
>>>>> This is going to change though with Couple CPUIDLE and corresponding
>>>>> OMAP updates.
>>>>
>>>>
>>>> Ok, thanks for the information. I will look deeper. What happens to cpu1
>>>> when it is online and has nothing to do ?
>>>>
>>>>>> and why the WFI is not used ?
>>>>>>
>>>>> I didn't get this question. Do you mean the generic WFI?
>>>>
>>>>
>>> I execute default idle loop.
>>
>>
>> So is it not possible to add a cpuidle device for cpu1 and define only one
>> state for the 'wfi-for-omap' ?
>>
> That's how my post was handling it. But after the review Kevin suggested
> me to drop the CPU1 shallow state since it was same as default idle.

Ok, thanks. I am asking that because the more I am looking at the 
different SoCs cpuidle drivers, the more I am convinced we can factor 
out more code across SoCs.

>>>> yes.
>>>>
>>>>> If yes, then, it's mainly because OMAP need additional
>>>>> custom barriers.
>>>>
>>>>
>>>> Ah, ok. I am not sure if it is possible but that may be cool if we can
>>>> call cpu_do_idle instead with additional barrier.
>>>>
>>> There is no need. Since code around WFI is customised, it make no sense
>>> to call cpu_do_idle(0 ofr only that instruction sake.
>>
>>
>> For my personal information, why the WFI is customised for omap4 ?
>>
> OMAP4 silicon has couple of hardware issues around interconnect
> and needs to drain the axi buffers with strongly order writes to
> ensure that data reaches to peripherals and not get stuck. That
> lead to have custom function. Note that, the wfi instruction
> itself is same.

Thanks for the explanation.

   -- Daniel

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