linux-kernel - Re: [PATCH 0/2] opp: core: add regulators enable and disable

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Message-ID: <20220905043543.huxq7mmpclto2h7k@vireshk-i7>
Date:   Mon, 5 Sep 2022 10:05:43 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Clément Péron <peron.clem@...il.com>
Cc:     k.konieczny@...sung.com,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>,
        "open list:ALLWINNER CPUFREQ DRIVER" <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Mark Brown <broonie@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] opp: core: add regulators enable and disable

On 03-09-22, 22:35, Clément Péron wrote:
> Today, I compiled my kernel without any program requiring GPU
> computing at boot. This makes the dev_pm_opp_set_rate() to never be
> called and so the regulator is not enabled before the regulator
> framework switches off all the regulators that haven't been enabled.
> 
> Unfortunately switching off the GPU regulator makes my board hang..

Why does the board hang? I mean the kernel should boot fine with the
GPU disabled, isn't it ? Or is the regulator shared with some other
critical resource, or something else.

> I'm not sure what is the best approach to fix this.
> 
> Is it required that the dev_pm_opp_set_rate() must be called one time
> at the GPU driver init?

Right now, Yes. And it looks like the right approach as well.

> Panfost already calls devfreq_recommended_opp() and dev_pm_opp_put()
> but that doesn't trigger dev_pm_opp_set_rate().

Can you also point to your code ? Which file are you working on ?

-- 
viresh