Re: [PATCH v2 1/2] devicetree: add binding for generic mmio clocksource

[Rob Herring]

+Stephen who has worked on this code.

On Fri, Oct 9, 2015 at 11:19 AM, MÃns RullgÃrd <mans@xxxxxxxxx> wrote:
> MÃns RullgÃrd <mans@xxxxxxxxx> writes:
>
>> Rob Herring <robherring2@xxxxxxxxx> writes:
>>
>>> On Wed, Oct 7, 2015 at 11:47 AM, MÃns RullgÃrd <mans@xxxxxxxxx> wrote:
>>>> What would be a proper way to select a sched_clock source?  I realise
>>>> it's a Linux-specific thing and DT is supposed to be generic, but the
>>>> information must be provided somehow.
>>>
>>> The kernel already has some logic to do this. Most number of bits
>>> followed by highest frequency will be the winning sched_clock. You
>>> might also want to look at things like always on or not.
>>
>> The problem is that sched_clock_register() doesn't take a pointer to be
>> passed back to the read_sched_clock callback like most interfaces of
>> this type do.  This means the callback must use global variables set up
>> before the register call, but at that time there's no way of knowing
>> which one will be used.  If there were a way of getting a pointer to the
>> callback, it would be a simple matter of registering all instances and
>> letting the kernel choose which to use.
>
> Anyone got a comment on this?  Do I have to send a patch adding this
> before anyone will tell me why it's a bad idea?  (That method almost
> always works.)

Adding a ptr to the callback seems fine to me.

Rob
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