Message-ID: <YW2/A4ZQwbFX0uPB@smile.fi.intel.com>
Date:   Mon, 18 Oct 2021 21:37:55 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Emil Renner Berthing <kernel@...il.dk>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        Drew Fustini <drew@...gleboard.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Anup Patel <anup.patel@....com>,
        Atish Patra <atish.patra@....com>,
        Matteo Croce <mcroce@...rosoft.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Huan Feng <huan.feng@...rfivetech.com>
Subject: Re: [PATCH v1 12/16] pinctrl: starfive: Add pinctrl driver for
 StarFive SoCs

On Mon, Oct 18, 2021 at 06:35:10PM +0200, Emil Renner Berthing wrote:
> On Mon, 18 Oct 2021 at 18:24, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > On Mon, Oct 18, 2021 at 6:56 PM Emil Renner Berthing <kernel@...il.dk> wrote:
> > > On Mon, 18 Oct 2021 at 17:48, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > > > On Mon, Oct 18, 2021 at 6:35 PM Emil Renner Berthing <kernel@...il.dk> wrote:
> > > > > On Tue, 12 Oct 2021 at 19:03, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > > > > > On Tue, Oct 12, 2021 at 4:43 PM Emil Renner Berthing <kernel@...il.dk> wrote:

...

> > > > > > > +               case PIN_CONFIG_BIAS_DISABLE:
> > > > > >
> > > > > > > +                       mask |= PAD_BIAS_MASK;
> > > > > >
> > > > > > Use it...
> > > > > >
> > > > > > > +                       value = (value & ~PAD_BIAS_MASK) | PAD_BIAS_DISABLE;
> > > > > >
> > > > > > ...here. Ditto for the similar cases in this function and elsewhere.
> > > > >
> > > > > I don't follow. How do you want me to use mask? If I did value =
> > > > > (value & ~mask) | PAD_BIAS_DISABLE; then I'd wipe the previous
> > > > > configuration. Eg. suppose the first config is the drive strength and
> > > > > second disables bias. Then on the 2nd loop mask =
> > > > > PAD_DRIVE_STRENGTH_MASK | PAD_BIAS_MASK and the drive strength value
> > > > > would be wiped.
> > > >
> > > > Collect masks and new values in temporary variables and apply them
> > > > once after the loop is done, no?
> > >
> > > But that's exactly what the code does. It merges all the config
> > > options into a single mask and value so we only need to do rmw on the
> > > register once.
> >
> > Then masking the value makes no sense.
> > What you should have is simply as
> >
> >   mask |= FOO;
> >   value |= BAR;
> 
> Yeah, but then we could get into weird states if the device tree
> specifies both bias-disable and bias-pull-up by mistake. This code is
> written so that only the last valid state is chosen.

But shouldn't it be disallowed by:
 1) DTC validator (Rob?)
 2) GPIO / pin control (Linus, Bart?)
?

...

> > > > > > > +       ret = clk_prepare_enable(clk);
> > > > > > > +       if (ret) {
> > > > > >
> > > > > > > +               reset_control_deassert(rst);
> > > > > >
> > > > > > Use devm_add_action_or_reset().
> > > > >
> > > > > I don't see how that is better.
> > > >
> > > > Pity. The rule of thumb is to either try to use devm_*() everywhere in
> > > > the probe, or don't use it at all. Above is the more-or-less standard
> > > > pattern where devn_add_action_or_reset() is being used in the entire
> > > > kernel.
> > > >
> > > > > Then I'd first need to call that and
> > > > > check for errors, but just on the line below enabling the clock the
> > > > > reset line is deasserted anyway, so then the action isn't needed any
> > > > > longer. So that 3 lines of code for devm_add_action_or_reset +
> > > > > lingering unneeded action or code to remove it again vs. just the line
> > > > > above.
> > > >
> > > > Then don't use devm_*() at all. What's the point?
> > >
> > > I'm confused. So you wan't an unneeded action to linger because the
> > > probe function temporarily asserts reset for 3 lines of code?
> >
> > I;m talking about clk_prepare_enable().
> 
> Ok, you wrote your comment under the reset_control_deassert call. How
> would devm_add_action_or_reset for clk_prepare_enable work?

It seems both are needed to be converted, otherwise _everything_ after
reset_assert() should not be devm_*().

TL;DR: the rule is
  Allowed:	devm_*() followed by non-devm_*()
  NOT allowed:	devm_*() followed by non-devm_*() followed by devm_*()

Of course, you may try to work the latter one, but it diminishes the whole
idea behind it, that's why I told that may be not using devm_*() is the
correct approach here and that what you meant (?).

The example how to use above mentioned API, just grep for it.

# See [1] for the sources of the used script
$ gl4func.sh devm_add_action_or_reset clk_prepare_enable | wc -l
101


[1]: https://github.com/andy-shev/home-bin-tools/blob/master/gl4func.sh

-- 
With Best Regards,
Andy Shevchenko

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