linux-kernel - Re: [PATCH v4 2/2] regulator: add QCOM RPMh regulator driver

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Date:   Wed, 30 May 2018 16:58:54 -0700
From:   David Collins <collinsd@...eaurora.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-msm@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v4 2/2] regulator: add QCOM RPMh regulator driver

Hello Doug,

On 05/29/2018 10:32 PM, Doug Anderson wrote:
> On Tue, May 22, 2018 at 7:43 PM, David Collins <collinsd@...eaurora.org> wrote:
>> + * @ever_enabled:              Boolean indicating that the regulator has been
>> + *                             explicitly enabled at least once.  Voltage
>> + *                             requests should be cached when this flag is not
>> + *                             set.
> 
> Do you really need this extra boolean?  Can't you just check if
> "enabled" is still "-EINVAL"?  If it is then you don't pass the
> voltage along.
> 
> ...this would mean that you'd also need to send the voltage vote when
> the regulator core tries to disable unused regulators at the end of
> bootup, but that should be OK right?  If we never touched a regulator
> anywhere at probe time and we're about to vote to disable it, we know
> there's nobody requiring it to still be on.  We can vote for the
> voltage now without fear of messing up a vote that the BIOS left in
> place.
> 
> In theory this should also allow you to assert your vote about the
> voltage of a regulator that has never been enabled, which (if I
> understand correctly) you consider to be a feature.

Removing 'ever_enabled' and caching the voltage when 'enabled == -EINVAL'
seems workable.  I'm a little concerned about this resulting in voltage =
regulator-min-microvolt requests being sent for all regulators that are
not explicitly enabled by Linux consumers before late_initcall_sync().
Theoretically all of the boot loader hand-off cases should be taken care
of by this point so it should be safe.

I'll make this change.

Take care,
David

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