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

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Date:   Mon, 29 Jul 2019 09:12:18 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Chen-Yu Tsai <wens@...e.org>
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

Hello,

On Mon, Jul 29, 2019 at 02:43:23PM +0800, Chen-Yu Tsai wrote:
> On Mon, Jul 29, 2019 at 2:36 PM Uwe Kleine-König
> <u.kleine-koenig@...gutronix.de> wrote:
> > On Fri, Jul 26, 2019 at 08:40:41PM +0200, Jernej Skrabec wrote:
> > > @@ -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.

If the device tree is wrong it is considered ok that the driver doesn't
behave correctly. So this is not a problem you need (or should) care
about.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |