linux-kernel - Re: [PATCH v3] iio: humidity: hdc100x: Add margin to the conversion time

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Date:   Sun, 18 Jul 2021 14:31:28 -0700
From:   Matt Ranostay <matt.ranostay@...sulko.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Chris Lesiak <chris.lesiak@...or.com>,
        "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] iio: humidity: hdc100x: Add margin to the conversion time

On Sun, Jul 18, 2021 at 7:49 AM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Wed, 16 Jun 2021 13:43:35 +0100
> Jonathan Cameron <jic23@...nel.org> wrote:
>
> > On Mon, 14 Jun 2021 09:18:20 -0500
> > Chris Lesiak <chris.lesiak@...or.com> wrote:
> >
> > > The datasheets have the following note for the conversion time
> > > specification: "This parameter is specified by design and/or
> > > characterization and it is not tested in production."
> > >
> > > Parts have been seen that require more time to do 14-bit conversions for
> > > the relative humidity channel.  The result is ENXIO due to the address
> > > phase of a transfer not getting an ACK.
> > >
> > > Delay an additional 1 ms per conversion to allow for additional margin.
> > >
> > > Fixes: 4839367d99e3 ("iio: humidity: add HDC100x support")
> > > Signed-off-by: Chris Lesiak <chris.lesiak@...or.com>
> >
> > +CC Matt as this is one of his drivers.
>
> @Matt. Ping.
>
> >
> > Looks good to me.

Looks good to me as well.

Acked-by: Matt Ranostay <matt.ranostay@...sulko.com>

> >
> > > ---
> > >  drivers/iio/humidity/hdc100x.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c
> > > index 2a957f19048e..9e0fce917ce4 100644
> > > --- a/drivers/iio/humidity/hdc100x.c
> > > +++ b/drivers/iio/humidity/hdc100x.c
> > > @@ -25,6 +25,8 @@
> > >  #include <linux/iio/trigger_consumer.h>
> > >  #include <linux/iio/triggered_buffer.h>
> > >
> > > +#include <linux/time.h>
> > > +
> > >  #define HDC100X_REG_TEMP                   0x00
> > >  #define HDC100X_REG_HUMIDITY                       0x01
> > >
> > > @@ -166,7 +168,7 @@ static int hdc100x_get_measurement(struct hdc100x_data *data,
> > >                                struct iio_chan_spec const *chan)
> > >  {
> > >     struct i2c_client *client = data->client;
> > > -   int delay = data->adc_int_us[chan->address];
> > > +   int delay = data->adc_int_us[chan->address] + 1*USEC_PER_MSEC;
> > >     int ret;
> > >     __be16 val;
> > >
> > > @@ -316,7 +318,7 @@ static irqreturn_t hdc100x_trigger_handler(int irq, void *p)
> > >     struct iio_dev *indio_dev = pf->indio_dev;
> > >     struct hdc100x_data *data = iio_priv(indio_dev);
> > >     struct i2c_client *client = data->client;
> > > -   int delay = data->adc_int_us[0] + data->adc_int_us[1];
> > > +   int delay = data->adc_int_us[0] + data->adc_int_us[1] + 2*USEC_PER_MSEC;
> > >     int ret;
> > >
> > >     /* dual read starts at temp register */
> >
>