Re: [PATCH v4 3/5] ARM: topology: Update cpu_power according to DT information

["Shilimkar, Santosh" <santosh.shilimkar@xxxxxx>]

On Mon, Jul 9, 2012 at 8:40 PM, Vincent Guittot
<vincent.guittot@xxxxxxxxxx> wrote:
> On 9 July 2012 16:37, Shilimkar, Santosh <santosh.shilimkar@xxxxxx> wrote:
>> On Mon, Jul 9, 2012 at 8:06 PM, Vincent Guittot
>> <vincent.guittot@xxxxxxxxxx> wrote:
>>> On 9 July 2012 15:00, Shilimkar, Santosh <santosh.shilimkar@xxxxxx> wrote:
>>>> On Mon, Jul 9, 2012 at 6:02 PM, Vincent Guittot
>>>> <vincent.guittot@xxxxxxxxxx> wrote:
>>>>> On 9 July 2012 12:55, Shilimkar, Santosh <santosh.shilimkar@xxxxxx> wrote:
>>>>>> Vincent,
>>>>>> On Mon, Jul 9, 2012 at 2:57 PM, Vincent Guittot
>>>>>> <vincent.guittot@xxxxxxxxxx> wrote:
>>>>>>> Use cpu compatibility field and clock-frequency field of DT to
>>>>>>> estimate the capacity of each core of the system and to update
>>>>>>> the cpu_power field accordingly.
>>>>>>> This patch enables to put more running tasks on big cores than
>>>>>>> on LITTLE ones. But this patch doesn't ensure that long running
>>>>>>> tasks will run on big cores and short ones on LITTLE cores.
>>>>>>>
>>>>>>> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>>>>>>> Reviewed-by: Namhyung Kim <namhyung@xxxxxxxxxx>
>>>>>>> ---
>>>>>>>  arch/arm/kernel/topology.c |  153 ++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>  1 file changed, 153 insertions(+)
>>>>>>>
>>>>>> Sorry for not giving this comment on previous version but we should also
>>>>>> have a way to provide the big.LITTLE information without Device Tree.
>>>>>> May be a platform device/data.
>>>>>
>>>>> Hi Santosh,
>>>>>
>>>>> I had thought of adding such additional way to set cpu_power of
>>>>> big.LITTLE but my conclusion was
>>>>> -it's a new platform so it should come with DT
>>>>> -DT is already required by other patches linked to big.LITTLE
>>>>> (http://lists.infradead.org/pipermail/linux-arm-kernel/2012-January/080873.html)
>>>>> -There is no device that can be easily used to get such information at
>>>>> this early boot stage.
>>>>>
>>>> I see. Its new processor but it is just 1 one of the IP in an entire SOC.
>>>> As mentioned below I was talking about full SOC support including
>>>> all the driver subsystem with DT.
>>>>
>>>>>>
>>>>>> I know we are moving DT way, but remember apart from core kernel
>>>>>> infrastructure, to have a complete product build with DT means all the
>>>>>> drivers must be already supporting DT which is not the case with
>>>>>> many huge driver sub-systems like USB, display subsystem, Audio etc.
>>>>>>
>>>>>> Having that support would greatly help for the SOC's which have not yet
>>>>>> reached to stage where entire SOC is DT compliant and want to use
>>>>>> big.LITTLE infrastructure.
>>>>>
>>>>> Can't you support both type of devices on your platform ? You can move
>>>>> your device to DT mode when it is supported ?
>>>>>
>>>> That is what eventually people end up doing who don't have
>>>> DT ready for entire SOC. I was trying to ask whether at least some
>>>> method is proposed(need not be merged in mainline) to have
>>>> the big.LITTLE information parsing without DT.
>>>
>>> Ok, IIUC, you need a temporary methods, which doesn't need to be
>>> merged in mainline, to set the cpu_scale field ?
>>>
>> Yep.
>
> You could use set_power_scale in your platform code to set the
> cpu_power of your CPUs until DT is ready for your platform.
>
Thanks for the clarification. Will try that out.

Regards
Santosh

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