Re: [PATCH] iio: resolver: ad2s1210: add support for adi,fixed-mode

[David Lechner]

On Fri, Oct 13, 2023 at 2:50 AM Nuno Sá <noname.nuno@xxxxxxxxx> wrote:
>
> Hi David,
>
> Couple of minor things...
>
> On Thu, 2023-10-12 at 15:45 -0500, David Lechner wrote:
> > It is possible to use the AD2S1210 with hardwired mode pins (A0 and A1).
> > According to the devicetree bindings, in this case the adi,fixed-mode
> > property will specify which of the 3 possible modes the mode pins are
> > hardwired for and the gpio-modes property is not allowed.
> >
> > This adds support for the case where the mode pins are hardwired for
> > config mode. In this configuration, the position and velocity must be read
> > from the config register.
> >
> > The cases of hardwired position or velocity modes is not supported as
> > there would be no way to configure the device.
> >
> > Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> > ---
> >  drivers/iio/resolver/ad2s1210.c | 193 +++++++++++++++++++++++++++-----
> >  1 file changed, 162 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/iio/resolver/ad2s1210.c b/drivers/iio/resolver/ad2s1210.c
> > index 1bd1b950e7cc..e6d3f31d529f 100644
> > --- a/drivers/iio/resolver/ad2s1210.c
> > +++ b/drivers/iio/resolver/ad2s1210.c
> > @@ -141,7 +141,7 @@ struct ad2s1210_state {
> >       struct spi_device *sdev;
> >       /** GPIO pin connected to SAMPLE line. */
> >       struct gpio_desc *sample_gpio;
> > -     /** GPIO pins connected to A0 and A1 lines. */
> > +     /** GPIO pins connected to A0 and A1 lines (optional). */
> >       struct gpio_descs *mode_gpios;
> >       /** Used to access config registers. */
> >       struct regmap *regmap;
> > @@ -149,6 +149,8 @@ struct ad2s1210_state {
> >       unsigned long clkin_hz;
> >       /** Available raw hysteresis values based on resolution. */
> >       int hysteresis_available[2];
> > +     /* adi,fixed-mode property - only valid when mode_gpios == NULL. */
> > +     enum ad2s1210_mode fixed_mode;
> >       /** The selected resolution */
> >       enum ad2s1210_resolution resolution;
> >       /** Copy of fault register from the previous read. */
> > @@ -175,6 +177,9 @@ static int ad2s1210_set_mode(struct ad2s1210_state *st,
> > enum ad2s1210_mode mode)
> >       struct gpio_descs *gpios = st->mode_gpios;
> >       DECLARE_BITMAP(bitmap, 2);
> >
> > +     if (!gpios)
> > +             return mode == st->fixed_mode ? 0 : -EOPNOTSUPP;
> > +
> >       bitmap[0] = mode;
> >
> >       return gpiod_set_array_value(gpios->ndescs, gpios->desc, gpios->info,
> > @@ -276,7 +281,8 @@ static int ad2s1210_regmap_reg_read(void *context,
> > unsigned int reg,
> >        * parity error. The fault register is read-only and the D7 bit means
> >        * something else there.
> >        */
> > -     if (reg != AD2S1210_REG_FAULT && st->rx[1] & AD2S1210_ADDRESS_DATA)
> > +     if ((reg > AD2S1210_REG_VELOCITY_LSB && reg != AD2S1210_REG_FAULT)
> > +          && st->rx[1] & AD2S1210_ADDRESS_DATA)
> >               return -EBADMSG;
> >
> >       *val = st->rx[1];
> > @@ -437,6 +443,40 @@ static void ad2s1210_push_events(struct iio_dev
> > *indio_dev,
> >       st->prev_fault_flags = flags;
> >  }
> >
> > +/**
> > + * Reads position or velocity from the config registers.
> > + *
> > + * This is used when the mode gpios are not available.
> > + *
> > + * Must be called with the lock held.
> > + *
> > + * @param st The device state.
> > + * @param val Pointer to hold the value read.
> > + * @param msb_reg The register address of the MSB register.
> > + * @param lsb_reg The register address of the LSB register.
> > + * @return 0 on success, negative error code otherwise.
> > + */
> > +static int ad2s1210_read_val_from_config(struct ad2s1210_state *st, __be16
> > *val,
> > +                                      u8 msb_reg, u8 lsb_reg)
> > +{
> > +     unsigned int reg_val;
> > +     int ret;
> > +
> > +     ret = regmap_read(st->regmap, msb_reg, &reg_val);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ((u8 *)val)[0] = reg_val;
> > +
> > +     ret = regmap_read(st->regmap, lsb_reg, &reg_val);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ((u8 *)val)[1] = reg_val;
>
> These casts are not that nice... Is sparse even ok with this without __force?
> I didn't looked at the datasheet so I have no idea but is regmap_bulk_read() an
> option? It would simplify things.

regmap_bulk_read() does work, thanks for the suggestion.

>
> > +
> > +     return 0;
> > +}
>
> ...
>
> >
> >       ad2s1210_push_events(indio_dev, st->sample.fault, pf->timestamp);
> > @@ -1299,9 +1397,33 @@ static const struct iio_info ad2s1210_info = {
> >  static int ad2s1210_setup_properties(struct ad2s1210_state *st)
> >  {
> >       struct device *dev = &st->sdev->dev;
> > +     const char *str_val;
> >       u32 val;
> >       int ret;
> >
> > +     ret = device_property_read_string(dev, "adi,fixed-mode", &str_val);
> > +     if (ret == -EINVAL)
> > +             st->fixed_mode = -1;
> > +     else if (ret < 0)
> > +             return dev_err_probe(dev, ret,
> > +                     "failed to read adi,fixed-mode property\n");
> > +     else {
> > +             if (strcmp(str_val, "position") == 0)
> > +                     st->fixed_mode = MOD_POS;
> > +             else if (strcmp(str_val, "velocity") == 0)
> > +                     st->fixed_mode = MOD_VEL;
> > +             else if (strcmp(str_val, "config") == 0)
> > +                     st->fixed_mode = MOD_CONFIG;
> > +             else
> > +                     return dev_err_probe(dev, -EINVAL,
> > +                             "invalid adi,fixed-mode property value:
> > %s\n",
> > +                             str_val);
> > +
> > +             if (st->fixed_mode != MOD_CONFIG)
> > +                     return dev_err_probe(dev, -EINVAL,
> > +                             "only adi,fixed-mode=\"config\" is
> > supported\n");
>
> Why not?
>
> if (strcmp(str_val, "config"))
>         return dev_err_probe();
>
> st->fixed_mode = MOD_CONFIG;
>
> Am I missing something obvious?

I made different error messages to differentiate between values not
allowed by the device tree vs. not supported by the driver. I don't
have a problem with simplifying it though.

>
> - Nuno Sá