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

[Robert Foss <robert.foss@linaro.org>]

Hey Andy,

Thanks for the review, it is much appreciated!

On Tue, 31 Mar 2020 at 16:01, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
>
> On Tue, Mar 31, 2020 at 4:36 PM Robert Foss <robert.foss@linaro.org> wrote:
> >
> > Add devicetree match table, and enable ov8856_probe()
> > to initialize power, clocks and reset pins.
>
> ...
>
> > +static int __ov8856_power_on(struct ov8856 *ov8856)
> > +{
> > +       struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
> > +       int ret;
> > +
> > +       ret = clk_prepare_enable(ov8856->xvclk);
> > +       if (ret < 0) {
> > +               dev_err(&client->dev, "failed to enable xvclk\n");
> > +               return ret;
> > +       }
> > +
>
> > +       if (is_acpi_node(ov8856->dev->fwnode))
>
> Use dev_fwnode().

Ack.

>
> > +               return 0;
> > +
> > +       if (ov8856->reset_gpio) {
>
> > +               gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
>
> This is wrong. You have to fix it to use either 0 or 1.

I've changed all gpiod_set_value_cansleep() calls to use 0/1.

>
> > +               usleep_range(1000, 2000);
> > +       }
> > +
> > +       ret = regulator_bulk_enable(ARRAY_SIZE(ov8856_supply_names),
> > +                                   ov8856->supplies);
>
> > +       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.

>
> > +               dev_err(&client->dev, "failed to enable regulators\n");
> > +               goto disable_clk;
> > +       }
>
> ...
>
> > +       gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_LOW);
>
> Ditto.

Ack.

>
> ...
>
> > +       gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
>
> Ditto.

Ack.

>
> ...
>
> > +       gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
>
> Ditto.

Ack.

>
> ...
>
> > -       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.

>
> > +       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.

>
> > +               return PTR_ERR(ov8856->xvclk);
> > +       }
>
> > +       ov8856->reset_gpio = devm_gpiod_get_optional(dev, "reset",
> > +               GPIOD_OUT_HIGH);
>
> Here parameter is correct. The question is, what the value should be
> HIGH or LOW?
> Basically HIGH means to assert the signal.

Ack, I'll invert the logic.

>
> > +       if (IS_ERR(ov8856->reset_gpio)) {
>
> > +               dev_dbg(dev, "failed to get reset-gpio\n");
>
> Noise.
> Enable GPIO debug to see this kind of messages.

Ack.

>
> > +               return PTR_ERR(ov8856->reset_gpio);
> > +       }
>
> ...
>
> > +       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.

>
> > +               return ret;
> >         }
>
> --
> With Best Regards,
> Andy Shevchenko

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