Re: [PATCH 2/2] ieee802154: mcr20a: Remove struct mcr20a_platform_data

[Xue Liu <liuxuenetmail@gmail.com>]

Hi Stefan,
On Thu, 27 Sep 2018 at 17:44, Stefan Schmidt <stefan@datenfreihafen.org> wrote:
>
> Hello Xue.
>
> On 31/08/2018 23:46, Xue Liu wrote:
> > The struct mcr20a_platform_data is uesed only in probe function
> > and it holds only one member. So it is not necessary to reserve it.
> >
> > Using gpiod family API to handle reset pin.
> >
> > Signed-off-by: Xue Liu <liuxuenetmail@gmail.com>
> > ---
> >  drivers/net/ieee802154/mcr20a.c | 64 +++++++--------------------------
> >  1 file changed, 13 insertions(+), 51 deletions(-)
> >
> > diff --git a/drivers/net/ieee802154/mcr20a.c b/drivers/net/ieee802154/mcr20a.c
> > index 04891429a554..44de81e5f140 100644
> > --- a/drivers/net/ieee802154/mcr20a.c
> > +++ b/drivers/net/ieee802154/mcr20a.c
> > @@ -132,11 +132,6 @@ static const struct reg_sequence mar20a_iar_overwrites[] = {
> >  };
> >
> >  #define MCR20A_VALID_CHANNELS (0x07FFF800)
> > -
> > -struct mcr20a_platform_data {
> > -     int rst_gpio;
> > -};
> > -
> >  #define MCR20A_MAX_BUF               (127)
> >
> >  #define printdev(X) (&X->spi->dev)
> > @@ -412,7 +407,6 @@ struct mcr20a_local {
> >       struct spi_device *spi;
> >
> >       struct ieee802154_hw *hw;
> > -     struct mcr20a_platform_data *pdata;
> >       struct regmap *regmap_dar;
> >       struct regmap *regmap_iar;
> >
> > @@ -976,20 +970,6 @@ static irqreturn_t mcr20a_irq_isr(int irq, void *data)
> >       return IRQ_HANDLED;
> >  }
> >
> > -static int mcr20a_get_platform_data(struct spi_device *spi,
> > -                                 struct mcr20a_platform_data *pdata)
> > -{
> > -     int ret = 0;
> > -
> > -     if (!spi->dev.of_node)
> > -             return -EINVAL;
> > -
> > -     pdata->rst_gpio = of_get_named_gpio(spi->dev.of_node, "rst_b-gpio", 0);
> > -     dev_dbg(&spi->dev, "rst_b-gpio: %d\n", pdata->rst_gpio);
> > -
> > -     return ret;
> > -}
> > -
> >  static void mcr20a_hw_setup(struct mcr20a_local *lp)
> >  {
> >       u8 i;
> > @@ -1249,7 +1229,7 @@ mcr20a_probe(struct spi_device *spi)
> >  {
> >       struct ieee802154_hw *hw;
> >       struct mcr20a_local *lp;
> > -     struct mcr20a_platform_data *pdata;
> > +     struct gpio_desc *rst_b;
> >       int irq_type;
> >       int ret = -ENOMEM;
> >
> > @@ -1260,48 +1240,32 @@ mcr20a_probe(struct spi_device *spi)
> >               return -EINVAL;
> >       }
> >
> > -     pdata = kmalloc(sizeof(*pdata), GFP_KERNEL);
> > -     if (!pdata)
> > -             return -ENOMEM;
> > -
> > -     /* set mcr20a platform data */
> > -     ret = mcr20a_get_platform_data(spi, pdata);
> > -     if (ret < 0) {
> > -             dev_crit(&spi->dev, "mcr20a_get_platform_data failed.\n");
> > -             goto free_pdata;
> > -     }
> > -
> > -     /* init reset gpio */
> > -     if (gpio_is_valid(pdata->rst_gpio)) {
> > -             ret = devm_gpio_request_one(&spi->dev, pdata->rst_gpio,
> > -                                         GPIOF_OUT_INIT_HIGH, "reset");
> > -             if (ret)
> > -                     goto free_pdata;
> > +     rst_b = devm_gpiod_get(&spi->dev, "rst_b", GPIOD_OUT_HIGH);
>
> I am a bit confused about the pin name here. When using
> of_get_named_gpio() the name is "rst_b-gpio" which is the same I see
> referenced in the devicetree bindings file.
>
> When switching to devm_gpiod_get() the name is shortened to "rst_b".
> Does the gpiod API implicitly add a -gpio to the name when searching for
> it in the dst?
>
Yes. The function calling tree is shown below:
--> devm_gpiod_get()
    --> __gpiod_get_index()
         --> of_find_gpio()
The definition of function of_find_gpio() is here
https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpiolib-of.c#L231.
The definition of struct gpio_suffixes is here
https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpiolib.h#L95.
You can see that the suffix "gpio" or "gpios" is automatically added
when it is looking for the name of gpio in the device tree.

> The reason I ask is that I would want to avoid a name change of the
> property. That would break the dts bindings already in place.
>
We don't need to change the dts bindings.

> > +     if (IS_ERR(rst_b)) {
> > +             ret = PTR_ERR(rst_b);
> > +             if (ret != -EPROBE_DEFER)
> > +                     dev_err(&spi->dev, "Failed to get 'rst_b' gpio: %d", ret);
> > +             return ret;
> >       }
> >
> >       /* reset mcr20a */
> > -     if (gpio_is_valid(pdata->rst_gpio)) {
> > -             usleep_range(10, 20);
> > -             gpio_set_value_cansleep(pdata->rst_gpio, 0);
> > -             usleep_range(10, 20);
> > -             gpio_set_value_cansleep(pdata->rst_gpio, 1);
> > -             usleep_range(120, 240);
> > -     }
> > +     usleep_range(10, 20);
> > +     gpiod_set_value_cansleep(rst_b, 1);
> > +     usleep_range(10, 20);
> > +     gpiod_set_value_cansleep(rst_b, 0);
> > +     usleep_range(120, 240);
>
> With your change you reversing the setting from ->0->1 to ->1->0. Is the
> gpiod API reverse here or did you made a copy and paste mistake? :-)
>
I am afraid both of assumptions are wrong here. The new GPIO
descriptor consumer interface uses *logical* value.
It means 0 and 1 denote GPIO deassertion and assertion. The property
of rst_b is GPIO_ACTIVE_LOW. So the value 1
means low in physical line and the value 0 means high.

Please reference
https://www.kernel.org/doc/Documentation/gpio/consumer.txt for more
information.

> >
> >       /* allocate ieee802154_hw and private data */
> >       hw = ieee802154_alloc_hw(sizeof(*lp), &mcr20a_hw_ops);
> >       if (!hw) {
> >               dev_crit(&spi->dev, "ieee802154_alloc_hw failed\n");
> > -             ret = -ENOMEM;
> > -             goto free_pdata;
> > +             return ret;
> >       }
> >
> >       /* init mcr20a local data */
> >       lp = hw->priv;
> >       lp->hw = hw;
> >       lp->spi = spi;
> > -     lp->spi->dev.platform_data = pdata;
> > -     lp->pdata = pdata;
> >
> >       /* init ieee802154_hw */
> >       hw->parent = &spi->dev;
> > @@ -1370,8 +1334,6 @@ mcr20a_probe(struct spi_device *spi)
> >
> >  free_dev:
> >       ieee802154_free_hw(lp->hw);
> > -free_pdata:
> > -     kfree(pdata);
> >
> >       return ret;
> >  }
> >
>
> The rest looks good to me and I like that we can get rid of all the
> boiler code associated with the pdata.
>
> If you could clarify (and potentially fix) the two points I raised I
> would be happy to apply this.
>
> regards
> Stefan Schmidt

regards

Xue Liu

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