linux-kernel - Re: [PATCH v1 12/16] pinctrl: starfive: Add pinctrl driver for StarFive SoCs

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Message-ID: <CANBLGcw1qMB7r7TbuQEevOPHq94wAtZNs=yFQ3UP_DEREvGz6g@mail.gmail.com>
Date:   Mon, 18 Oct 2021 18:35:10 +0200
From:   Emil Renner Berthing <kernel@...il.dk>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        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, 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.


> ...
>
> > > > > > +       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?

> ...
>
> > > > > > +       sfp->gc.of_node = dev->of_node;
> > > > >
> > > > > Isn't GPIO library do this for you?
> > > >
> > > > If it does I can't find it.
> > >
> > > Heh... `man git grep`
> > > Hint: `git grep -n 'of_node = .*of_node' -- drivers/gpio/gpiolib*`
> >
> > That's exactly what I did.
>
> Now look at the result and find the correct place where it's done.
> Btw, all hits are in the very same function.
>
> --
> With Best Regards,
> Andy Shevchenko