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Date: Sun, 22 May 2022 11:42:43 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Eddie James <eajames@...ux.ibm.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
lars@...afoo.de, joel@....id.au
Subject: Re: [PATCH] iio: pressure: dps310: Reset chip if MEAS_CFG is
corrupt
On Wed, 18 May 2022 09:07:08 -0500
Eddie James <eajames@...ux.ibm.com> wrote:
> On 5/14/22 10:02, Jonathan Cameron wrote:
> > On Wed, 11 May 2022 14:27:24 -0500
> > Eddie James <eajames@...ux.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 write all the necessary registers.
> >>
> >> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> > It's a large patch, so not an ideal 'fix' to backport, but
> > if we need to for platforms to work we should do so.
> >
> > Hence, please add a Fixes tag (which I'm guessing will be the driver
> > being added in the first place).
> >
> > Whilst tidying up might be nice, we shouldn't do refactoring that's not
> > strictly necessary in a fix patch. Hence I'd prefer this as a two patch
> > series. Refactor with no functional changes, then the actual change.
>
>
> Sure thing.
>
>
> >
> > A couple of minor queries inline,
> >
> > Thanks,
> >
> > Jonathan
> >
> >
> >
> >> ---
> >> drivers/iio/pressure/dps310.c | 280 +++++++++++++++++++++-------------
> >> 1 file changed, 173 insertions(+), 107 deletions(-)
> >>
> >> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
> >> index 36fb7ae0d0a9..39f84614f44e 100644
> >> --- a/drivers/iio/pressure/dps310.c
> >> +++ b/drivers/iio/pressure/dps310.c
> >> @@ -159,6 +159,106 @@ static int dps310_get_coefs(struct dps310_data *data)
> >> return 0;
> >> }
> >>
> >> +/*
> >> + * Some verions of chip will read temperatures in the ~60C range when
> >> + * its actually ~20C. This is the manufacturer recommended workaround
> >> + * to correct the issue. The registers used below are undocumented.
> >> + */
> >> +static int dps310_temp_workaround(struct dps310_data *data)
> >> +{
> >> + int rc;
> >> + int reg;
> >> +
> >> + rc = regmap_read(data->regmap, 0x32, ®);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /*
> >> + * If bit 1 is set then the device is okay, and the workaround does not
> >> + * need to be applied
> >> + */
> >> + if (reg & BIT(1))
> >> + return 0;
> >> +
> >> + rc = regmap_write(data->regmap, 0x0e, 0xA5);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + rc = regmap_write(data->regmap, 0x0f, 0x96);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + rc = regmap_write(data->regmap, 0x62, 0x02);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + rc = regmap_write(data->regmap, 0x0e, 0x00);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + return regmap_write(data->regmap, 0x0f, 0x00);
> >> +}
> >> +
> >> +static int dps310_startup(struct dps310_data *data)
> >> +{
> >> + int rc;
> >> + int ready;
> >> +
> >> + /*
> >> + * Set up pressure sensor in single sample, one measurement per second
> >> + * mode
> >> + */
> >> + rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /*
> >> + * Set up external (MEMS) temperature sensor in single sample, one
> >> + * measurement per second mode
> >> + */
> >> + rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /* Temp and pressure shifts are disabled when PRC <= 8 */
> >> + rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> >> + DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /* MEAS_CFG doesn't update correctly unless first written with 0 */
> >> + rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> >> + DPS310_MEAS_CTRL_BITS, 0);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /* Turn on temperature and pressure measurement in the background */
> >> + rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> >> + DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
> >> + DPS310_TEMP_EN | DPS310_BACKGROUND);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + /*
> >> + * Calibration coefficients required for reporting temperature.
> >> + * They are available 40ms after the device has started
> >> + */
> >> + rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> >> + ready & DPS310_COEF_RDY, 10000, 40000);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + rc = dps310_get_coefs(data);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + rc = dps310_temp_workaround(data);
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + return 0;
> >> +}
> >> +
> >> static int dps310_get_pres_precision(struct dps310_data *data)
> >> {
> >> int rc;
> >> @@ -297,6 +397,38 @@ static int dps310_get_temp_k(struct dps310_data *data)
> >> return scale_factors[ilog2(rc)];
> >> }
> >>
> >> +/* Called with lock held */
> >> +static int dps310_verify_meas_cfg(struct dps310_data *data, int ready_bit)
> > Hmm. I'm not immediately coming up with a better name, but it does
> > seem odd that a verify function would do a reset.
>
>
> Sure, I'll try and think of a better name.
>
>
> >
> >> +{
> >> + int en = DPS310_PRS_EN | DPS310_TEMP_EN | DPS310_BACKGROUND;
> >> + int meas_cfg;
> >> + int rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &meas_cfg);
> >> +
> >> + if (rc < 0)
> >> + return rc;
> >> +
> >> + if (meas_cfg & ready_bit)
> >> + return 0;
> >> +
> >> + if ((meas_cfg & en) != en) {
> >> + /* 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);
> >> + 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;
> >> @@ -309,15 +441,25 @@ 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)
> >> - goto done;
> >> + rc = dps310_verify_meas_cfg(data, DPS310_PRS_RDY);
> >> + if (rc) {
> > So at this point we potentially reset. Is there a race condition against
> > the device register state corrupting again? If so I guess we are relying
> > on the timeout and userspace trying again. Maybe worth adding a comment
> > if that is the case.
>
>
> Well, I don't know what causes the corruption at this point. The lock is
> held, so nothing else should touch the device, so I'm assuming it won't
> get corrupted. And assuming the reset works, then the sensor measurement
> should return valid data now, so any problem should be invisible to
> userspace (except this read will take a long time).
Fair enough - I was guessing we were looking at noise / brownout or
similar causing a loss of register value. If we think it's related
to actual traffic (or don't know :) then I'm fine with this unless
we get reports of more problems even with this 'hack' in place.
Thanks,
Jonathan
>
>
> Thanks for the review.
>
> Eddie
>
>
> >
> >> + if (rc < 0)
> >> + goto done;
> >> +
> >> + 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)
> >> @@ -358,15 +500,25 @@ 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);
> >> - if (rc < 0)
> >> - goto done;
> >> + rc = dps310_verify_meas_cfg(data, DPS310_TMP_RDY);
> >> + if (rc) {
> >> + if (rc < 0)
> >> + goto done;
> >> +
> >> + 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);
> >>
> >> @@ -677,52 +829,12 @@ static const struct iio_info dps310_info = {
> >> .write_raw = dps310_write_raw,
> >> };
> >>
> >> -/*
> >> - * Some verions of chip will read temperatures in the ~60C range when
> >> - * its actually ~20C. This is the manufacturer recommended workaround
> >> - * to correct the issue. The registers used below are undocumented.
> >> - */
> >> -static int dps310_temp_workaround(struct dps310_data *data)
> >> -{
> >> - int rc;
> >> - int reg;
> >> -
> >> - rc = regmap_read(data->regmap, 0x32, ®);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - /*
> >> - * If bit 1 is set then the device is okay, and the workaround does not
> >> - * need to be applied
> >> - */
> >> - if (reg & BIT(1))
> >> - return 0;
> >> -
> >> - rc = regmap_write(data->regmap, 0x0e, 0xA5);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - rc = regmap_write(data->regmap, 0x0f, 0x96);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - rc = regmap_write(data->regmap, 0x62, 0x02);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - rc = regmap_write(data->regmap, 0x0e, 0x00);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - return regmap_write(data->regmap, 0x0f, 0x00);
> >> -}
> >> -
> >> static int dps310_probe(struct i2c_client *client,
> >> const struct i2c_device_id *id)
> >> {
> >> struct dps310_data *data;
> >> struct iio_dev *iio;
> >> - int rc, ready;
> >> + int rc;
> >>
> >> iio = devm_iio_device_alloc(&client->dev, sizeof(*data));
> >> if (!iio)
> >> @@ -747,54 +859,8 @@ static int dps310_probe(struct i2c_client *client,
> >> if (rc)
> >> return rc;
> >>
> >> - /*
> >> - * Set up pressure sensor in single sample, one measurement per second
> >> - * mode
> >> - */
> >> - rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);
> > Lack of error checking in original code is odd. Deliberate or not is the
> > question... (probably not deliberate as rc = is there).
> >
> >> -
> >> - /*
> >> - * Set up external (MEMS) temperature sensor in single sample, one
> >> - * measurement per second mode
> >> - */
> >> - rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - /* Temp and pressure shifts are disabled when PRC <= 8 */
> >> - rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
> >> - DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - /* MEAS_CFG doesn't update correctly unless first written with 0 */
> >> - rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> >> - DPS310_MEAS_CTRL_BITS, 0);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - /* Turn on temperature and pressure measurement in the background */
> >> - rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
> >> - DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
> >> - DPS310_TEMP_EN | DPS310_BACKGROUND);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - /*
> >> - * Calibration coefficients required for reporting temperature.
> >> - * They are available 40ms after the device has started
> >> - */
> >> - rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> >> - ready & DPS310_COEF_RDY, 10000, 40000);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - rc = dps310_get_coefs(data);
> >> - if (rc < 0)
> >> - return rc;
> >> -
> >> - rc = dps310_temp_workaround(data);
> >> - if (rc < 0)
> >> + rc = dps310_startup(data);
> >> + if (rc)
> >> return rc;
> >>
> >> rc = devm_iio_device_register(&client->dev, iio);
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