linux-kernel - Re: [PATCH RFT v1 1/3] drm/panfrost: enable devfreq based the "operating-points-v2" property

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Message-ID: <be59a20b-af08-5b55-fa69-f87d5aa9f277@arm.com>
Date:   Wed, 8 Jan 2020 14:20:21 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     dri-devel@...ts.freedesktop.org, alyssa@...enzweig.io,
        steven.price@....com, tomeu.vizoso@...labora.com, robh@...nel.org,
        linux-kernel@...r.kernel.org, daniel@...ll.ch, airlied@...ux.ie,
        linux-amlogic@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH RFT v1 1/3] drm/panfrost: enable devfreq based the
 "operating-points-v2" property

[ +Sudeep ]

On 08/01/2020 12:38 pm, Martin Blumenstingl wrote:
> Hi Robin,
> 
> On Wed, Jan 8, 2020 at 12:18 PM Robin Murphy <robin.murphy@....com> wrote:
>>
>> On 07/01/2020 11:06 pm, Martin Blumenstingl wrote:
>>> Decouple the check to see whether we want to enable devfreq for the GPU
>>> from dev_pm_opp_set_regulators(). This is preparation work for adding
>>> back support for regulator control (which means we need to call
>>> dev_pm_opp_set_regulators() before dev_pm_opp_of_add_table(), which
>>> means having a check for "is devfreq enabled" that is not tied to
>>> dev_pm_opp_of_add_table() makes things easier).
>>
>> Hmm, what about cases like the SCMI DVFS protocol where the OPPs are
>> dynamically discovered rather than statically defined in DT?
> where can I find such an example (Amlogic SoCs use SCPI instead of
> SCMI, so I don't think that I have any board with SCMI support) or
> some documentation?
> (I could only find SCPI clock and CPU DVFS implementations, but no
> generic "OPPs for any device" implementation)

On closer inspection I think this applies to the SCPI DVFS protocol 
too[1]. AIUI the fact that neither is wired up to a devfreq driver yet 
is merely due to lack of demand and suitable systems to develop/test on 
so far - the panfrost devfreq code is only now looking like the first 
viable upstream use-case ;)

Robin.

[1] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922g/BABFEBCD.html