On Sun, 24 Jul 2022 19:43:15 +0300
Matti Lehtimäki <matti.lehtimaki@xxxxxxxxx> wrote:
> Some sensors do not always start fast enough to read a valid ID from
> registers at first attempt. Let's retry at most 3 times with short sleep
> in between to fix random timing issues.
>
> Signed-off-by: Matti Lehtimäki <matti.lehtimaki@xxxxxxxxx>
Hi Matti,
My gut feeling is this isn't in a fast path, so why not just wait
for whatever the documented power up time of the sensor is?
I'd expect to see a sleep in st_sensors_power_enable() if one is
required.
Jonathan
> ---
> drivers/iio/common/st_sensors/st_sensors_core.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
> index 9910ba1da085..106f7953683e 100644
> --- a/drivers/iio/common/st_sensors/st_sensors_core.c
> +++ b/drivers/iio/common/st_sensors/st_sensors_core.c
> @@ -21,6 +21,8 @@
>
> #include "st_sensors_core.h"
>
> +#define VERIFY_ID_RETRY_COUNT 3
> +
> int st_sensors_write_data_with_mask(struct iio_dev *indio_dev,
> u8 reg_addr, u8 mask, u8 data)
> {
> @@ -619,11 +621,18 @@ EXPORT_SYMBOL_NS(st_sensors_get_settings_index, IIO_ST_SENSORS);
> int st_sensors_verify_id(struct iio_dev *indio_dev)
> {
> struct st_sensor_data *sdata = iio_priv(indio_dev);
> - int wai, err;
> + int wai, err, i;
>
> if (sdata->sensor_settings->wai_addr) {
> - err = regmap_read(sdata->regmap,
> - sdata->sensor_settings->wai_addr, &wai);
> + for (i = 0; i < VERIFY_ID_RETRY_COUNT; i++) {
> + err = regmap_read(sdata->regmap,
> + sdata->sensor_settings->wai_addr, &wai);
> +
> + if (!err && sdata->sensor_settings->wai == wai)
> + return 0;
> +
> + msleep(20);
How do we know 60msecs is long enough for all sensors?
> + }
> if (err < 0) {
> dev_err(&indio_dev->dev,
> "failed to read Who-Am-I register.\n");
