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

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Date:   Wed, 17 Jun 2020 13:06:01 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Sumit Semwal <sumit.semwal@...aro.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, 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?

> > > > > 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.

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