linux-kernel - Re: [v2 3/4] regulator: qcom: Add labibb driver

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Message-ID: <CAO_48GF0tjZDmTS+Fa4fv+cfH4skFZP_a9A=P7D0b_si4AFj5A@mail.gmail.com>
Date:   Wed, 27 May 2020 22:01:27 +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: [v2 3/4] regulator: qcom: Add labibb driver

Hello Mark,

On Thu, 14 May 2020 at 16:57, Sumit Semwal <sumit.semwal@...aro.org> wrote:
>
> Hello Mark,
>
> Thank you for your review comments!
> On Mon, 11 May 2020 at 16:09, Mark Brown <broonie@...nel.org> wrote:
> >
> > On Sat, May 09, 2020 at 02:11:59AM +0530, Sumit Semwal wrote:
> >
> > > +     ret = regmap_bulk_read(reg->regmap, reg->base +
> > > +                            REG_LABIBB_STATUS1, &val, 1);
> > > +     if (ret < 0) {
> > > +             dev_err(reg->dev, "Read register failed ret = %d\n", ret);
> > > +             return ret;
> > > +     }
> >
> > Why a bulk read of a single register?
> Right, will change.
> >
> > > +static int _check_enabled_with_retries(struct regulator_dev *rdev,
> > > +                     int retries, int enabled)
> > > +{
> >
> > This is not retrying, this is polling to see if the regulator actually
> > enabled.
> Yes, will update accordingly.
>
> >
> > > +static int qcom_labibb_regulator_enable(struct regulator_dev *rdev)
> > > +{
> >
> > > +     ret = _check_enabled_with_retries(rdev, retries, 1);
> > > +     if (ret < 0) {
> > > +             dev_err(reg->dev, "retries exhausted: enable %s regulator\n",
> > > +                     reg->desc.name);
> > > +             return ret;
> > > +     }
> >
> > If this is useful factor it out into a helper or the core, other devices
> > also have status bits saying if the regulator is enabled.  It looks like
> > this may be mainly trying to open code something like enable_time, with
> > possibly some issues where the time taken to enable varies a lot.
> >
> Makes sense; I am not terribly familiar with the regulator core and
> helpers, so let me look and refactor accordingly.
Does something like this make sense, or did I misunderstand your
suggestion completely? I'll send the updated patches accordingly.

--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2353,6 +2353,7 @@ static int _regulator_do_enable(struct
regulator_dev *rdev)
+       /* If max_time_poll_enabled is set for the regulator,
+        * Poll upto max_time_poll_enabled time to see if the regulator
+        * actually got enabled.
+        * For each iteration, wait for the enable_time delay calculated
+        * above already.
+        * If the regulator isn't enabled after max_time_poll_enabled has
+        * expired, return -REG_ENABLED_CHECK_FAILED.
+        */
+       if (rdev->desc->max_time_poll_enabled) {
+               unsigned int remaining_time_to_poll =
rdev->desc->max_time_poll_enabled;
+
+               while (remaining_time_to_poll > 0) {
+                       /* We've already waited for enable_time above;
+                        * so we can start with immediate check of the
+                        * status of the regulator.
+                        */
+                       if (rdev->desc->ops->is_enabled(rdev))
+                               break;
+
+                       _regulator_enable_delay(delay);
+                       remaining_time_to_poll -= delay;
+               }
+
+               if (remaining_time_to_poll <= 0) {
+                       rdev_err(rdev, "Enabled check failed.\n");
+                       return -REG_ENABLED_CHECK_FAILED;
+               }
+       }
+

Since atleast in my use case, the delay is really enable_time (time
before we could check the status register), we could reuse the
already-calculated 'delay' based on enable_time?
>
<snip>

Best,
Sumit.