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Message-ID: <a817037e-0c8f-a890-549a-6df42e2bb26d@linux.ibm.com>
Date: Tue, 24 May 2022 09:18:32 -0500
From: Eddie James <eajames@...ux.ibm.com>
To: Joel Stanley <joel@....id.au>
Cc: linux-iio@...r.kernel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH v2 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is
corrupt
On 5/23/22 21:12, Joel Stanley wrote:
> On Wed, 18 May 2022 at 14:48, 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 execute the startup procedure.
> I have some suggestions below on how to rework to make the code easier
> to understand. But before we got to that, I had some high level
> questions:
>
>
> You don't seem to be setting the en bits in the CFG register after
> doing the reset. Is that required?
It does set the enable bits in the startup procedure, called after the
reset.
>
> Are we ok to sleep for 2.5ms in the iio_info->read_raw callback?
I believe it's safe... the code already has a mutex, so its not called
in atomic context.
>
>
>> Fixes: ba6ec48e76bc ("iio: Add driver for Infineon DPS310")
>> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
>> ---
>> drivers/iio/pressure/dps310.c | 89 ++++++++++++++++++++++++++++-------
>> 1 file changed, 71 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
>> index f79b274bb38d..c6d02679ef33 100644
>> --- a/drivers/iio/pressure/dps310.c
>> +++ b/drivers/iio/pressure/dps310.c
>> @@ -397,6 +397,39 @@ static int dps310_get_temp_k(struct dps310_data *data)
>> return scale_factors[ilog2(rc)];
>> }
>>
>> +/* Called with lock held */
> Perhaps add this to your comment: Returns a negative value on error, a
> positive value when the device is not ready (and may have been reset
> due to corruption), and zero when the device is ready.
Good idea.
>
>> +static int dps310_check_reset_meas_cfg(struct dps310_data *data, int ready_bit)
>> +{
>> + 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;
> I'm confused about this case. We get there when the device doesn't
> have ready_bit set in meas_cfg and we've done a reset, but we also get
> here when the bit isn't set and we haven't done anything to resolve it
> (after re-reading the code I understand now, but perhaps reworking it
> as follows will make it clear):
>
> Could we write it like this:
>
> if (meas_cfg & ready_bit) {
> /* Device ready, must be okay */
> return 0;
> }
>
> if (meas_cfg & en) {
> /* Device okay (but not ready), no action required */
> return 1;
> }
>
> /* DPS310 register state corrupt, better start from scratch */
> ...
> return 1;
Yea it could be clearer, I can update that.
>
>
>> +}
>> +
>> static int dps310_read_pres_raw(struct dps310_data *data)
>> {
>> int rc;
>> @@ -409,15 +442,25 @@ 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_check_reset_meas_cfg(data, DPS310_PRS_RDY);
> can we do this:
>
> if (rc < 0)
> goto done;
>
> if (rc > 0) {
>
> }
>
> The rework I suggest makes it clearer that we've considered the '0'
> case, when the device is ready before this code runs.
Sure. Thanks for the review, I'll get a v3 up.
Thanks,
Eddie
>
>> + if (rc) {
>> + 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)
>> @@ -458,15 +501,25 @@ 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_check_reset_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);
>>
>> --
>> 2.27.0
>>
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