linux-kernel - Re: [PATCH v2 3/3] firmware: scpi: add device power domain support using genpd

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Date:	Mon, 20 Jun 2016 10:50:37 -0700
From:	Kevin Hilman <khilman@...libre.com>
To:	"Jon Medhurst \(Tixy\)" <tixy@...aro.org>
Cc:	Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2 3/3] firmware: scpi: add device power domain support using genpd

"Jon Medhurst (Tixy)" <tixy@...aro.org> writes:

> On Thu, 2016-06-16 at 18:59 +0100, Sudeep Holla wrote:
>> 
>> On 16/06/16 18:47, Jon Medhurst (Tixy) wrote:
>> > On Thu, 2016-06-16 at 11:38 +0100, Sudeep Holla wrote:
>> > [...]
>> >> +enum scpi_power_domain_state {
>> >> +	SCPI_PD_STATE_ON = 0,
>> >> +	SCPI_PD_STATE_OFF = 3,
>> >> +};
>> >
>> > The SCPI doc defines the meaning of these numbers (0 and 3) in the 'Juno
>> > specifics' chapter. So does these values need to come from device-tree
>> > to allow for other hardware or SCP implementations?
>> >
>> 
>> Ah unfortunately true :(. I had not noticed that. But I would like to
>> check if this can be made as part of the standard protocol. Adding such
>> details to DT seems overkill and defeat of the whole purpose of the
>> standard protocol.
>
> Well. it seems to me the 'standard protocol' is whatever the current
> implementation of ARM's closed source SCP firmware is. It also seems to
> me that people are making things up as they go along, without a clue as
> to how to make things generic, robust and future proof. Basically,
> Status Normal ARM Fucked Up.

Fully agree here.  Just because ARM calls it a "standard" does not make
it so.  As we've already seen[1], vendors are using initial/older/whatever
versions of SCPI, so pushing the Juno version as standard just becuase
it's in ARM's closed firmware is not the right way forward either.

Kevin

[1] http://marc.info/?l=linux-arm-kernel&m=146425562931515&w=2