RE: [PATCH 1/2] iio: ltc2983: add support for optional reset gpio

["Sa, Nuno" <Nuno.Sa@analog.com>]

> -----Original Message-----
> From: Alexandru Ardelean <ardeleanalex@gmail.com>
> Sent: Friday, August 20, 2021 10:21 AM
> To: Sa, Nuno <Nuno.Sa@analog.com>
> Cc: linux-iio <linux-iio@vger.kernel.org>; Jonathan Cameron
> <jic23@kernel.org>; Lars-Peter Clausen <lars@metafoo.de>; Drew
> Fustini <drew@pdp7.com>
> Subject: Re: [PATCH 1/2] iio: ltc2983: add support for optional reset
> gpio
> 
> [External]
> 
> On Fri, Aug 20, 2021 at 9:53 AM Nuno Sá <nuno.sa@analog.com>
> wrote:
> >
> > Check if an optional reset gpio is present and if so, make sure to
> reset
> > the device.
> >
> 
> Just one note/question inline.
> 
> > Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> > ---
> >  drivers/iio/temperature/ltc2983.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/iio/temperature/ltc2983.c
> b/drivers/iio/temperature/ltc2983.c
> > index 3b4a0e60e605..37903e9fb90f 100644
> > --- a/drivers/iio/temperature/ltc2983.c
> > +++ b/drivers/iio/temperature/ltc2983.c
> > @@ -1470,6 +1470,7 @@ static int ltc2983_probe(struct spi_device
> *spi)
> >  {
> >         struct ltc2983_data *st;
> >         struct iio_dev *indio_dev;
> > +       struct gpio_desc *gpio;
> >         const char *name = spi_get_device_id(spi)->name;
> >         int ret;
> >
> > @@ -1494,6 +1495,16 @@ static int ltc2983_probe(struct spi_device
> *spi)
> >         if (ret)
> >                 return ret;
> >
> > +       gpio = devm_gpiod_get_optional(&st->spi->dev, "reset",
> GPIOD_OUT_HIGH);
> > +       if (IS_ERR(gpio))
> > +               return PTR_ERR(gpio);
> > +
> > +       if (gpio) {
> > +               /* bring device out of reset */
> > +               usleep_range(1000, 1005);
> > +               gpiod_set_value_cansleep(gpio, 0);
> 
> Datasheet mentions that it takes up to 100 ms for the device to fully
> start-up.
> It also mentions that the (command) status register will be
> unavailable to the user before this point.
> Page 16, Conversion State Details section, second paragraph.
> 
> I think there should probably be a sleep here of 100 ms.
> 
> Other than that change looks good.
> 

In the setup function we do a polled read on the status register until
we get the indication we are up. This was actually a fix sent recently
[1].

[1]: https://patchwork.kernel.org/project/linux-iio/patch/20210811133220.190264-2-nuno.sa@analog.com/
- Nuno Sá

> > +       }
> > +
> >         ret = ltc2983_setup(st, true);
> >         if (ret)
> >                 return ret;
> > --
> > 2.33.0
> >