Re: [PATCH v4 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

[Eddie James]

On 8/12/22 17:13, Andy Shevchenko wrote:
> On Wed, Aug 10, 2022 at 12:12 AM Eddie James <eajames@xxxxxxxxxxxxx> wrote:
> > Corruption of the MEAS_CFG register has been observed soon after
> > system boot. In order to recover this scenario, check MEAS_CFG if
> > measurement isn't ready, and if it's incorrect, reset the DPS310
> > and execute the startup procedure.
> Looks like both patches miss the Fixes tag. Can you add them?


Well this isn't really a software fix - there's no identifiable bug in 
the driver. Just trying to recover the chip in this observed mystery 
scenario.


> ...
>
> > +/*
> > + * Called with lock held. Returns a negative value on error, a positive value
> > + * when the device is not ready, and zero when the device is ready.
> > + */
> > +static int dps310_check_reset_meas_cfg(struct dps310_data *data, int ready_bit)
> > +{
> > +       int meas_cfg;
> > +       int rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &meas_cfg);
> > +
> > +       if (rc < 0)
> > +               return rc;
> Please, split definition and assignment.


Ack.


> > +       /* Device is ready, proceed to measurement */
> > +       if (meas_cfg & ready_bit)
> > +               return 0;
> > +
> > +       /* Device is OK, just not ready */
> > +       if (meas_cfg & (DPS310_PRS_EN | DPS310_TEMP_EN | DPS310_BACKGROUND))
> > +               return 1;
> > +
> > +       /* DPS310 register state corrupt, better start from scratch */
> > +       rc = regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
> > +       if (rc < 0)
> > +               return rc;
> > +
> > +       /* Wait for device chip access: 2.5ms in specification */
> > +       usleep_range(2500, 12000);
> > +
> > +       /* Reinitialize the chip */
> > +       rc = dps310_startup(data);
> > +       if (rc)
> > +               return rc;
> > +
> > +       dev_info(&data->client->dev,
> > +                "recovered from corrupted MEAS_CFG=%02x\n", meas_cfg);
> > +       return 1;
> > +}
> > +
> >   static int dps310_read_pres_raw(struct dps310_data *data)
> >   {
> >          int rc;
> > @@ -405,16 +443,26 @@ static int dps310_read_pres_raw(struct dps310_data *data)
> >          if (mutex_lock_interruptible(&data->lock))
> >                  return -EINTR;
> >
> > -       rate = dps310_get_pres_samp_freq(data);
> > -       timeout = DPS310_POLL_TIMEOUT_US(rate);
> > -
> > -       /* Poll for sensor readiness; base the timeout upon the sample rate. */
> > -       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> > -                                     ready & DPS310_PRS_RDY,
> > -                                     DPS310_POLL_SLEEP_US(timeout), timeout);
> > -       if (rc)
> > +       rc = dps310_check_reset_meas_cfg(data, DPS310_PRS_RDY);
> > +       if (rc < 0)
> >                  goto done;
> >
> > +       if (rc > 0) {
> > +               rate = dps310_get_pres_samp_freq(data);
> > +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> > +
> > +               /*
> > +                * Poll for sensor readiness; base the timeout upon the sample
> > +                * rate.
> > +                */
> > +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> > +                                             ready, ready & DPS310_PRS_RDY,
> > +                                             DPS310_POLL_SLEEP_US(timeout),
> > +                                             timeout);
> > +               if (rc)
> > +                       goto done;
> > +       }
> If you split the condition body to a helper, it can be rewritten like
> (also note special definition for positive returned numbers):
>
>    rc = ..._reset_meas_cfg(...);
>    if (rc  == DPS310_MEAS_NOT_READY)
>      rc = ..._new_helper_func(...);
>    if (rc)
>      goto done;
>
> and looking at this it might be worth considering calling that
> conditional in the middle in the _reset_meas_cfg(), so the latter will
> return either 0 or negative error code.


To be honest that looks more complicated than the way it is now? And I 
don't think I can make it common between the temp and pressure without 
some complicated macro business.


> > +       rc = dps310_check_reset_meas_cfg(data, DPS310_TMP_RDY);
> >          if (rc < 0)
> >                  goto done;
> >
> > +       if (rc > 0) {
> > +               rate = dps310_get_temp_samp_freq(data);
> Okay, I see this function is different, but still you may realize a
> helper from below and something like above suggestion can still be
> achieved.
>
> > +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> > +
> > +               /*
> > +                * Poll for sensor readiness; base the timeout upon the sample
> > +                * rate.
> > +                */
> > +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> > +                                             ready, ready & DPS310_TMP_RDY,
> > +                                             DPS310_POLL_SLEEP_US(timeout),
> > +                                             timeout);
> > +               if (rc < 0)
> Why out of a sudden ' < 0'?


Good point, I'll fix that.


> > +                       goto done;
> > +       }
> As per above.
>
> >          rc = dps310_read_temp_ready(data);