Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for power-domains

From	Sudeep Holla <sudeep.holla@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for power-domains
Date	2017-05-03 13:30 +0200
Message-ID	<tD0DM-4DU-7@gated-at.bofh.it> (permalink)
References	(6 earlier) <txDRw-8e8-23@gated-at.bofh.it> <tAmU9-5O3-5@gated-at.bofh.it> <tAvE5-2Zp-3@gated-at.bofh.it> <tAOdH-76j-3@gated-at.bofh.it> <tBWsy-3iq-1@gated-at.bofh.it>
Organization	ARM

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On 30/04/17 13:49, Mark Brown wrote:
> On Thu, Apr 27, 2017 at 10:42:49AM +0100, Sudeep Holla wrote:
>> On 26/04/17 14:55, Mark Brown wrote:
> 
>>> As I'm getting fed up of saying: if the values you are setting are not
>>> voltages and do not behave like voltages then the hardware should not be
>>> represented as a voltage regulator since if they are represented as
>>> voltage regulators things will expect to be able to control them as
>>> voltage regulators.  This hardware is quite clearly providing OPPs
>>> directly, I would expect this to be handled in the OPP code somehow.
> 
>> I agree with you that we need to be absolutely sure on what it actually
>> represents.
> 
>> But as more and more platform are pushing such power controls to
>> dedicated M3 or similar processors, we need abstraction. Though we are
>> controlling hardware, we do so indirectly. Since there were discussions
>> around device tree representing hardware vs platform, I tend to think,
>> we are moving towards platform(something similar to ACPI).
> 
> I don't think there's a meaningful hardware/platform distinction here -
> in terms of what DT is describing the platform bit is just what the
> hardware (the microcontrollers) happen to do, 
> 

Yes agreed. It's similar to PSCI or any other platform firmware IMO.

The question is how do we deal with such controls that needs to be done
via the firmware ? We generally plug-in to the existing framework in
Linux using the existing bindings. Most of the time, much simpler
bindings than the one that present complete hardware description.

> DT doesn't much care about that though.

No sure about that, may be doesn't care about the internals, but we need
to care about interface, no ?

-- 
Regards,
Sudeep

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Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Rajendra Nayak <rnayak@codeaurora.org> - 2017-04-26 06:40 +0200
  Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Mark Brown <broonie@kernel.org> - 2017-04-26 16:00 +0200
    Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Sudeep Holla <sudeep.holla@arm.com> - 2017-04-27 11:50 +0200
      Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Rajendra Nayak <rnayak@codeaurora.org> - 2017-04-27 13:00 +0200
        Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Viresh Kumar <viresh.kumar@linaro.org> - 2017-04-28 07:10 +0200
          Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Sudeep Holla <sudeep.holla@arm.com> - 2017-04-28 11:50 +0200
            Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Viresh Kumar <viresh.kumar@linaro.org> - 2017-04-28 13:20 +0200
      Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Mark Brown <broonie@kernel.org> - 2017-04-30 14:50 +0200
        Re: [PATCH V4 1/9] PM / OPP: Allow OPP table to be used for  power-domains Sudeep Holla <sudeep.holla@arm.com> - 2017-05-03 13:30 +0200

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