linux-kernel - Re: [PATCH v4 4/5] regulator: qcom: Add labibb driver

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Message-ID: <CAO_48GGhX-AxjvvvPKRMc+LQ_Uws1s_b4Q+aHokVv2RxcpObQw@mail.gmail.com>
Date:   Wed, 17 Jun 2020 17:39:26 +0530
From:   Sumit Semwal <sumit.semwal@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     agross@...nel.org, Bjorn Andersson <bjorn.andersson@...aro.org>,
        lgirdwood@...il.com, robh+dt@...nel.org,
        Nisha Kumari <nishakumari@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org, kgunda@...eaurora.org,
        Rajendra Nayak <rnayak@...eaurora.org>
Subject: Re: [PATCH v4 4/5] regulator: qcom: Add labibb driver

On Wed, 17 Jun 2020 at 17:36, Mark Brown <broonie@...nel.org> wrote:
>
> On Wed, Jun 17, 2020 at 05:27:12PM +0530, Sumit Semwal wrote:
> > On Wed, 17 Jun 2020 at 17:17, Mark Brown <broonie@...nel.org> wrote:
> > > On Wed, Jun 17, 2020 at 05:12:35PM +0530, Sumit Semwal wrote:
>
> > > > I understand from a pure regulators' correctness point of view,
> > > > ENABLE_CTL should be the one checked there, so I can change the patch
> > > > as you suggested, but there seems to be some performance penalty
> > > > there.
>
> > > I thought the goal was to have the performance penalty to ensure that
> > > the regulator had actually started?
>
> > IMHO, with the poll_enabled_time mechanism added, we would not need to
> > wait for the full enabled_time time for the regulator to get enabled,
> > but we could poll (and potentially know earlier) if the regulator is
> > enabled.
> > The performance penalty I was talking, is about how should we check if
> > the regulator is really enabled or not - via reading the STATUS1
> > register, which seems to tell the status a bit faster, or via reading
> > the ENABLE_CTL register which we also use to enable/disable the
> > regulator, but which seems to be slower in updating the status.
>
> That seems...  interesting.  Are you sure the regulator has fully ramped
> when STATUS1 starts flagging?
On a consumer device, I am not sure I have any way of checking that,
but if there's some way you'd like me to validate it, I'll be happy
to.
>
> > > > > > The WARN_ON? This was suggested by Bjorn to catch the case where the
> > > > > > DT binding for a PMIC instantiates only one of the regulators.
>
> > > > > No, this whole loop - why this whole match and get child stuff?
>
> > > > This loop mechanism is what I saw in the other qcom regulators
> > > > upstream, so thought it was an acceptable way.
> > > > For the two children nodes, do you recommend another mechanism to get
> > > > and validate both nodes?
>
> > > I don't understand what you mean by "two children nodes" here?
>
> > The two 'lab' and 'ibb' regulator nodes that are part of the labibb node.
>
> Use of_match and regulators_node like other regulator drivers.

Ok, let me see what I can do with those; we still need to flag if some
platform only instantiates one of the two lab/ibb regulators - I was
given the impression they're 'both or none' case.

Best,
Sumit.