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References: <20220524201729.39503-1-eajames@linux.ibm.com> <20220524201729.39503-3-eajames@linux.ibm.com>
In-Reply-To: <20220524201729.39503-3-eajames@linux.ibm.com>
From:   Joel Stanley <joel@jms.id.au>
Date:   Wed, 25 May 2022 00:59:54 +0000
Message-ID: <CACPK8XdBSKEnOaORrjSeZEYjV8yhgxStUZ0TdTk2H7NQHioFow@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt
To:     Eddie James <eajames@linux.ibm.com>
Cc:     linux-iio@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Jonathan Cameron <jic23@kernel.org>
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On Tue, 24 May 2022 at 20:17, Eddie James <eajames@linux.ibm.com> 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.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

Reviewed-by: Joel Stanley <joel@jms.id.au>

> ---
>  drivers/iio/pressure/dps310.c | 88 +++++++++++++++++++++++++++++------
>  1 file changed, 73 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> index f79b274bb38d..fbceaa2cd71c 100644
> --- a/drivers/iio/pressure/dps310.c
> +++ b/drivers/iio/pressure/dps310.c
> @@ -397,6 +397,44 @@ static int dps310_get_temp_k(struct dps310_data *data)
>         return scale_factors[ilog2(rc)];
>  }
>
> +/*
> + * 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;
> +
> +       /* 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;
> @@ -409,16 +447,26 @@ 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;
> +       }
> +
>         rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
>         if (rc < 0)
>                 goto done;
> @@ -458,16 +506,26 @@ static int dps310_read_temp_raw(struct dps310_data *data)
>         if (mutex_lock_interruptible(&data->lock))
>                 return -EINTR;
>
> -       rate = dps310_get_temp_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_TMP_RDY,
> -                                     DPS310_POLL_SLEEP_US(timeout), timeout);
> +       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);
> +               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)
> +                       goto done;
> +       }
> +
>         rc = dps310_read_temp_ready(data);
>
>  done:
> --
> 2.27.0
>