linux-kernel - Re: [PATCH 0/2] cpufreq/opp: rework regulator initialization

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Message-ID: <20190208115122.GA13043@e107155-lin>
Date:   Fri, 8 Feb 2019 11:51:22 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Dave Gerlach <d-gerlach@...com>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH 0/2] cpufreq/opp: rework regulator initialization

On Fri, Feb 08, 2019 at 12:47:06PM +0100, Marek Szyprowski wrote:
> Hi Sudeep,
>
> On 2019-02-08 12:00, Sudeep Holla wrote:
> > On Thu, Feb 07, 2019 at 01:22:25PM +0100, Marek Szyprowski wrote:
> >> Dear All,
> >>
> >> This is a scenario that triggers the above issue:
> > [...]
> >> 1. system disables non-boot cpu's at the end of system suspend procedure,
> >> 2. this in turn deinitializes cpufreq drivers for the disabled cpus,
> >> 3. early in the system resume procedure all cpus are got back to online
> >>    state,
> >> 4. this in turn causes cpufreq to be initialized for the newly onlined
> >>    cpus,
> >> 5. cpufreq-dt acquires all its resources (clocks, regulators) during
> >>    ->init() callback,
> > This is strictly not just restricted to cpufreq-dt, but to any driver
> > supporting multiple policies. So we need a generic fix not just
> > cpufreq-dt specific.
>
> Could you point which other driver needs similar fix? Here in cpufreq-dt
> the problem was caused by using regulator api (indirectly) from
> ->init(). All other drivers, which have regulators support, are for old,
> obsolete, uni-processor systems, which don't have the problem of
> secondary cpu suspend during system suspend/resume cycle.
>

scmi_cpufreq for instance. We can fix that in driver my moving to polling
to get cpufreq_get_rate, but we support both polling and interrupt based.
We may wait for remote processor interrupt in get_rate.

--
Regards,
Sudeep