linux-kernel - Re: [PATCH 2/6] pwm: sun4i: Add a quirk for reset line

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Date:   Mon, 29 Jul 2019 14:43:23 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Jernej Skrabec <jernej.skrabec@...l.net>,
        Thierry Reding <thierry.reding@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pwm@...r.kernel.org,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Philipp Zabel <p.zabel@...gutronix.de>
Subject: Re: [PATCH 2/6] pwm: sun4i: Add a quirk for reset line

On Mon, Jul 29, 2019 at 2:36 PM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
>
> Cc += reset framework maintainer
>
> Hello Jernej,
>
> On Fri, Jul 26, 2019 at 08:40:41PM +0200, Jernej Skrabec wrote:
> > H6 PWM core needs deasserted reset line in order to work.
> >
> > Add a quirk for it.
> >
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> > ---
> >  drivers/pwm/pwm-sun4i.c | 27 +++++++++++++++++++++++++--
> >  1 file changed, 25 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> > index de78c824bbfd..1b7be8fbde86 100644
> > --- a/drivers/pwm/pwm-sun4i.c
> > +++ b/drivers/pwm/pwm-sun4i.c
> > @@ -16,6 +16,7 @@
> >  #include <linux/of_device.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/pwm.h>
> > +#include <linux/reset.h>
> >  #include <linux/slab.h>
> >  #include <linux/spinlock.h>
> >  #include <linux/time.h>
> > @@ -72,12 +73,14 @@ static const u32 prescaler_table[] = {
> >
> >  struct sun4i_pwm_data {
> >       bool has_prescaler_bypass;
> > +     bool has_reset;
> >       unsigned int npwm;
> >  };
> >
> >  struct sun4i_pwm_chip {
> >       struct pwm_chip chip;
> >       struct clk *clk;
> > +     struct reset_control *rst;
> >       void __iomem *base;
> >       spinlock_t ctrl_lock;
> >       const struct sun4i_pwm_data *data;
> > @@ -371,6 +374,14 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> >       if (IS_ERR(pwm->clk))
> >               return PTR_ERR(pwm->clk);
> >
> > +     if (pwm->data->has_reset) {
> > +             pwm->rst = devm_reset_control_get(&pdev->dev, NULL);
> > +             if (IS_ERR(pwm->rst))
> > +                     return PTR_ERR(pwm->rst);
> > +
> > +             reset_control_deassert(pwm->rst);
> > +     }
> > +
>
> I wonder why there is a need to track if a given chip needs a reset
> line. I'd just use devm_reset_control_get_optional() and drop the
> .has_reset member in struct sun4i_pwm_data.

Because it's not optional for this platform, i.e. it won't work if
the reset control (or clk, in the next patch) is somehow missing from
the device tree.

ChenYu

> >       pwm->chip.dev = &pdev->dev;
> >       pwm->chip.ops = &sun4i_pwm_ops;
> >       pwm->chip.base = -1;
> > @@ -383,19 +394,31 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> >       ret = pwmchip_add(&pwm->chip);
> >       if (ret < 0) {
> >               dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
> > -             return ret;
> > +             goto err_pwm_add;
> >       }
> >
> >       platform_set_drvdata(pdev, pwm);
> >
> >       return 0;
> > +
> > +err_pwm_add:
> > +     reset_control_assert(pwm->rst);
> > +
> > +     return ret;
> >  }
> >
> >  static int sun4i_pwm_remove(struct platform_device *pdev)
> >  {
> >       struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);
> > +     int ret;
> > +
> > +     ret = pwmchip_remove(&pwm->chip);
> > +     if (ret)
> > +             return ret;
> >
> > -     return pwmchip_remove(&pwm->chip);
> > +     reset_control_assert(pwm->rst);
> > +
> > +     return 0;
> >  }
> >
> >  static struct platform_driver sun4i_pwm_driver = {
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |