linux-kernel - Re: [PATCH V6 1/9] PM / OPP: Introduce "power-domain-opp" property

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Date:   Mon, 8 May 2017 12:43:50 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Rob Herring <robh@...nel.org>, Rafael Wysocki <rjw@...ysocki.net>,
        ulf.hansson@...aro.org, Kevin Hilman <khilman@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        lina.iyer@...aro.org, rnayak@...eaurora.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V6 1/9] PM / OPP: Introduce "power-domain-opp" property

On 03-05-17, 12:29, Sudeep Holla wrote:
> 
> 
> On 28/04/17 21:48, Rob Herring wrote:
> > On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote:
> >> Power-domains need to express their active states in DT and the devices
> >> within the power-domain need to express their dependency on those active
> >> states. The power-domains can use the OPP tables without any
> >> modifications to the bindings.
> >>
> >> Add a new property "power-domain-opp", which will contain phandle to the
> >> OPP node of the parent power domain. This is required for devices which
> >> have dependency on the configured active state of the power domain for
> >> their working.
> >>
> >> For some platforms the actual frequency and voltages of the power
> >> domains are managed by the firmware and are so hidden from the high
> >> level operating system. The "opp-hz" property is relaxed a bit to
> >> contain indexes instead of actual frequency values to support such
> >> platforms.
> >>
> >> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> >> ---
> >>  Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++-
> >>  1 file changed, 73 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> >> index 63725498bd20..6e30cae2a936 100644
> >> --- a/Documentation/devicetree/bindings/opp/opp.txt
> >> +++ b/Documentation/devicetree/bindings/opp/opp.txt
> >> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related
> >>  properties.
> >>  
> >>  Required properties:
> >> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.
> >> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some
> >> +  cases the exact frequency in Hz may be hidden from the OS by the firmware and
> >> +  this field may contain values that represent the frequency in a firmware
> >> +  dependent way, for example an index of an array in the firmware.
> > 
> > Not really sure OPP binding makes sense here. What about all the other 
> > properties. We expose voltage, but not freq?
> > 
> 
> I completely agree with that and I have been pushing this to be
> represented as just regulators[0]. Mark B seem to dislike that
> idea [1]

Just as an update, Rajendra confirmed (offline) that for some of the
implementations, the microcontroller handles both frequency and
voltages of a device. So it isn't just a regulator anymore and as me
and Kevin were saying, we need a complete OPP here.

-- 
viresh