linux-kernel - RE: [PATCH 8/9] regulator: bd71837: BD71837 PMIC regulator driver

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Message-ID: <042F8805D2046347BB8420BEAE397A4016C06B60@WILL-MAIL002.REu.RohmEu.com>
Date:   Thu, 24 May 2018 17:51:27 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     Mark Brown <broonie@...nel.org>
CC:     "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Mutanen, Mikko" <Mikko.Mutanen@...rohmeurope.com>,
        "Haikola, Heikki" <Heikki.Haikola@...rohmeurope.com>
Subject: RE: [PATCH 8/9] regulator: bd71837: BD71837 PMIC regulator driver


From: Mark Brown [broonie@...nel.org]
> Sent: Thursday, May 24, 2018 5:14 PM
>
> On Thu, May 24, 2018 at 09:00:36AM +0300, Matti Vaittinen wrote:
>
> > @@ -0,0 +1,683 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (C) 2018 ROHM Semiconductors */
> > +/*
> > + * bd71837-regulator.c ROHM BD71837MWV regulator driver
> > + */
> > +#include <linux/kernel.h>
>
> Make the entire comment block a C++ comment so it looks more intentional

I will change this to C++ - but the verison of checkpatch.pl I used did complain
if I used C++ style comments in C-files or if I used C-style comments in header.
I guess the sscript should be fixed unless it is already done.

> and add a blank line before the headers for legibility.
Will do.

> > +static int bd71837_regulator_set_regmap(struct regulator_dev *rdev, int set)
> > +{
> > +     int ret = -EINVAL;
> > +     struct bd71837_pmic *pmic = rdev->reg_data;
> > +
> > +     if (pmic) {
> > +             mutex_lock(&pmic->mtx);
> > +             if (!set)
> > +                     ret = regulator_disable_regmap(rdev);
> > +             else
> > +                     ret = regulator_enable_regmap(rdev);
> > +             mutex_unlock(&pmic->mtx);
> > +     }
>
> This looks very weird - why might we not have a parent PMIC,
I'll remove the check. I've just adopted habit of adding NULL checks
for pointers "jsut in case".

> what is the lock doing and what is this wrapper function intended to do?
This was the other spot which I was unsure how to handle. Datasheet for
the chip says that if voltage is to be changed, the regulator must be
disabled. Thus my voltage changing function checks if regulator is enabled
and disables it for duration of voltage change (if it was enabled). This lock
is used to protect the voltage change so that no one enables the regulator
during voltage change. I don't know what would have been correct way of
doing this, or if disabling regulator for voltage change is Ok - but this was
the only way I could think of. I am again grateful for any tips.

> Similar
> issues apply to the voltage functions, if there's any need for this it
> needs to be better documented but it really doesn't look like a good
> idea.
If the solution with lock and wrapper (to prevent race during state check
and voltage change) is Ok, then I will add comment which explains this,

> > +     err =
> > +         regmap_update_bits(pmic->mfd->regmap, BD71837_REG_REGLOCK,
> > +                            (REGLOCK_PWRSEQ | REGLOCK_VREG), 0);
> > +     if (err) {
> > +             dev_err(&pmic->pdev->dev, "Failed to unlock PMIC (%d)\n", err);
> > +             goto err;
> > +     } else
> > +             dev_dbg(&pmic->pdev->dev, "%s: Unlocked lock register 0x%x\n",
> > +                     __func__, BD71837_REG_REGLOCK);
>
> There's loads of coding style problems with this code, please refer to
> the coding style - indentation is weird and if there's { } on one side
> of an else it should be on both.

Will fix it.

> > +             rdev = regulator_register(desc, &config);
> > +             if (IS_ERR(rdev)) {
>
> devm_regulator_regster()

Makes sense. Thanks


Best Regards
    Matti Vaittinen