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From: Niklas Cassel <nks@flawful.org>
To: Stephan Gerhold <stephan@gerhold.net>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
	Loic Poulain <loic.poulain@linaro.org>,
	agross@kernel.org, linux-arm-msm@vger.kernel.org,
	Viresh Kumar <vireshk@kernel.org>
Subject: Re: [PATCH] arch: arm64: dts: apq8016-dbc: Add missing cpu opps
Date: Thu, 28 May 2020 01:10:25 +0200	[thread overview]
Message-ID: <20200527231025.GA32707@flawful.org> (raw)
In-Reply-To: <20200527205518.GA8254@gerhold.net>

On Wed, May 27, 2020 at 10:56:07PM +0200, Stephan Gerhold wrote:
> > If the CPR driver is not changed, which I doubt, you will simply change
> > the device tree to remove the cpu-supply regulator and move it into the
> > new CPR DT node.
> > 
> > Old device trees will still use your DVFS solution, new device
> > trees will use the CPR DT node and will use the AVS solution.
> > 
> 
> I think my concern is essentially that I would duplicate the MEMACC code
> into a new driver utilizing .set_opp() - and to keep backwards
> compatibility we would need to keep that duplication forever.

The cleanest solution is probably to create a new memacc platform device
driver, and make the new code use that, and refactor CPR to use the same.

> 
> The MEMACC scaling isn't all that complicated, but overall I would
> prefer to avoid introducing duplication in the first place.
> 
> Also: If full CPR ever happens we would be basically back
> to one part of the current discussion: specifying two "required-opps"
> MX and CPR (= APC + MEMACC) would result in the wrong order
> when scaling up/down.
> 
> But maybe I just worry too much?

I guess that whoever implements CPR on msm8916 will either call
dev_pm_genpd_set_performance_state() on MX directly from cpr_scale_voltage()
or perhaps change OPP core so that it runs the required-opps in reverse
order when scaling down, like you previously suggested.

Please don't take my suggestions as the only way forward though.
Hopefully I provided more clarity than confusion.
Will step back so that someone else has a chance to chime in :)


Kind regards,
Niklas

  reply	other threads:[~2020-05-27 23:10 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-01 17:50 [PATCH] arch: arm64: dts: apq8016-dbc: Add missing cpu opps Loic Poulain
2020-04-01 23:46 ` Bjorn Andersson
2020-04-02  8:13 ` Stephan Gerhold
2020-04-02  9:58   ` Loic Poulain
2020-04-03  1:31   ` Bjorn Andersson
2020-04-03 10:09     ` Stephan Gerhold
2020-04-03 18:00       ` Stephan Gerhold
2020-04-23  4:55         ` Bjorn Andersson
2020-04-26 12:31           ` Stephan Gerhold
2020-05-06 21:18             ` Stephan Gerhold
2020-05-07  5:34               ` Bjorn Andersson
2020-05-08 12:08                 ` Ulf Hansson
2020-05-08 13:42                   ` Stephan Gerhold
2020-05-11  5:29                   ` Viresh Kumar
2020-05-07 10:46               ` Stephan Gerhold
2020-05-21 19:18                 ` Stephan Gerhold
2020-05-23 12:08                   ` Stephan Gerhold
2020-05-27 20:47                     ` Georgi Djakov
2020-05-25 15:32           ` Niklas Cassel
2020-05-25 16:36             ` Stephan Gerhold
2020-05-25 19:44               ` Niklas Cassel
2020-05-26  8:59                 ` Stephan Gerhold
2020-05-26 15:54                   ` Niklas Cassel
2020-05-26 20:54                     ` Stephan Gerhold
2020-05-27 10:39                       ` Niklas Cassel
2020-05-27 12:04                         ` Stephan Gerhold
2020-05-27 12:59                           ` Niklas Cassel
2020-05-27 20:56                             ` Stephan Gerhold
2020-05-27 23:10                               ` Niklas Cassel [this message]
2020-05-28 13:32                                 ` Stephan Gerhold
2020-05-28  4:44                           ` Viresh Kumar
2020-04-28 20:04 ` Amit Kucheria

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