[PATCH] radeon: Make PM info available to all, not just debug users

[Jerome Glisse]

On Mon, Jun 4, 2012 at 11:02 AM, Martin Peres <martin.peres at free.fr> wrote:
> Le 04/06/2012 16:31, Jerome Glisse a écrit :
>
>>
>> I don't think sysfs is the way to go, i am pretty sure that power
>> management will change drasticly again in the future especialy btw
>> discret and integrated GPU. I would rather have hardware specific
>> ioctl.
>>
>> Cheers,
>> Jerome
>
> Any particular idea of what may change?
>
> The proposed interface would work even on entirely dynamic
> reclocking (per-domain frequency scaling) as opposed to
> perflvl-based reclocking. It is unlikely to happen though.
>
> A more realistic possibility could be that engines would be reclocked
> independently according to their internal load.
> If that was to happen, then the already-existing API could be used as
> a master control and engines could specify the performance level policy
> they want (follow master, always min, always max, conservative, dynamic).
>
> I'm pretty sure voltage domains will soon appear but I don't see what could
> possibly be changed that wouldn't be covered by what I proposed.
>
> As for the reason we would like to use IOCTLs instead of sysfs, I really
> don't understand what is the rationale. I personally want to empower the
> users to let them decide what is best for them. Sysfs is way easier to
> work with!
>
> Although my idea may be sketchy, I am dead-serious about coming up with
> a good API.
>
> Martin

My experience is that things that are true today for GPU, are not
tomorrow. Yes there will still be clock/voltage, but there could be
new complete different things, like shutting down block.

I am not even mentioning things like complex value range dependency
btw things (for instance if a domain as clock/voltage in certain range
than some other domain can only have clock in a restricted range
value).

While i agree that sysfs looks easy for user to play with, i believe
that gui is what you really after and afaik closed source driver all
expose a gui for their power management. Using ioctl allow better
overall control, like atomic setting of several domain ...

Cheers,
Jerome