linux-kernel - Re: [PATCH v3 2/3] media: ov8856: Add devicetree support

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Date:   Mon, 6 Apr 2020 18:06:26 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Robert Foss <robert.foss@...aro.org>
Cc:     Dongchun Zhu <dongchun.zhu@...iatek.com>,
        Fabio Estevam <festevam@...il.com>,
        Sakari Ailus <sakari.ailus@....fi>,
        Tomasz Figa <tfiga@...omium.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 2/3] media: ov8856: Add devicetree support

On Mon, Apr 06, 2020 at 03:37:24PM +0200, Robert Foss wrote:
> On Tue, 31 Mar 2020 at 16:01, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > On Tue, Mar 31, 2020 at 4:36 PM Robert Foss <robert.foss@...aro.org> wrote:

...

> > > +       if (ret < 0) {
> >
> > Do you need all ' < 0' parts all over the series?
> 
> Some checks are needed due to ACPI and DT support co-existing.
> Maybe it would be better to just split the probing into an ACPI path
> and a DT path.
> 
> I'll have a look through the series for redundant retval checks.

Drop where it is redundant.

...

> > > -       ret = fwnode_property_read_u32(fwnode, "clock-frequency", &mclk);
> > > -       if (ret)
> > > -               return ret;
> >
> > Where is it gone? Why?
> 
> It was replaced by a clk_get_rate call, which as Sakari pointed out,
> isn't correct.
> I'll rework the clock handling for v4.

If it was in the driver it should stay -- properties is an ABI (between firmware and kernel).

> > > +       ov8856->xvclk = devm_clk_get_optional(dev, "xvclk");
> > > +       if (IS_ERR(ov8856->xvclk)) {
> >
> > > +               dev_err(dev, "could not get xvclk clock (%ld)\n",
> > > +                       PTR_ERR(ov8856->xvclk));
> >
> > Also you may use %pe here and in similar cases.
> 
> Weirdly checkpatch complains about this.
> But it builds and runs cleanly, so I'll add it in v4.

%pe requires pointer, PTR_ERR converts pointer to integer.

...

> > > +       ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ov8856_supply_names),
> > > +                                     ov8856->supplies);
> > > +       if (ret) {
> >
> > > +               dev_warn(dev, "failed to get regulators\n");
> >
> > If it's a warning, why we return from here?
> > Same question to all other places with same issue.
> 
> The issue I was seeing was the driver having to return a EDEFER here,
> so this warning sheds some light on which exact component is returning
> an EDEFER.
> 
> [   15.962623] ov8856 16-0010: Dropping the link to regulator.29
> [   15.968464] ov8856 16-0010: failed to get regulators
> [   15.973493] ov8856 16-0010: failed to get HW configuration: -517
> [   15.979591] ov8856 16-0010: removing from PM domain titan_top_gdsc
> [   15.985855] ov8856 16-0010: genpd_remove_device()
> [   15.990672] i2c 16-0010: Driver ov8856 requests probe deferral
> 
> Personally I found it helpful to speed up debugging, but I'll happily
> remove it if you prefer no warning.

My point is that you have it in align:
 - if it is an error, print as an error and bail out, otherwise
 - if it is a warning, print it and continue.

> > > +               return ret;
> > >         }

-- 
With Best Regards,
Andy Shevchenko