Re: [PATCH 5/6] iio:common:ms_sensors:ms_sensors_i2c: add support for alternative PROM layout

Jonathan Cameron
2020-12-13T17:21:44Z

On Thu, 10 Dec 2020 00:48:56 +0100
Alexandre Belloni <alexandre.belloni@bootlin.com> wrote:

> Currently, only the 112bit PROM on 7 words is supported. However the ms58xx

PROM _with_ 7 words (perhaps?)

> family also have devices with a 128bit PROM on 8 words. See AN520:
> C-CODE EXAMPLE FOR MS56XX, MS57XX (EXCEPT ANALOG SENSOR), AND MS58XX SERIES
> PRESSURE SENSORS and the various device datasheets.
>
> The difference is that the CRC is the 4 LSBs of word7 instead of being the
> 4 MSBs of word0.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
> .../iio/common/ms_sensors/ms_sensors_i2c.c | 70 ++++++++++++++++---
> 1 file changed, 59 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
> index 872f90459e2e..d97ca3e1b1d7 100644
> --- a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
> +++ b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
> @@ -488,21 +488,18 @@ int ms_sensors_ht_read_humidity(struct ms_ht_dev *dev_data,
> EXPORT_SYMBOL(ms_sensors_ht_read_humidity);
>
> /**
> - * ms_sensors_tp_crc_valid() - CRC check function for
> + * ms_sensors_tp_crc4() - Calculate PROM CRC for
> * Temperature and pressure devices.
> * This function is only used when reading PROM coefficients
> *
> * @prom: pointer to PROM coefficients array
> *
> - * Return: True if CRC is ok.
> + * Return: CRC.
> */
> -static bool ms_sensors_tp_crc_valid(u16 *prom)
> +static u8 ms_sensors_tp_crc4(u16 *prom)
> {
> unsigned int cnt, n_bit;
> - u16 n_rem = 0x0000, crc_read = prom[0], crc = (*prom & 0xF000) >> 12;
> -
> - prom[MS_SENSORS_TP_PROM_WORDS_NB - 1] = 0;
> - prom[0] &= 0x0FFF; /* Clear the CRC computation part */
> + u16 n_rem = 0x0000;
>
> for (cnt = 0; cnt < MS_SENSORS_TP_PROM_WORDS_NB * 2; cnt++) {
> if (cnt % 2 == 1)
> @@ -517,10 +514,55 @@ static bool ms_sensors_tp_crc_valid(u16 *prom)
> n_rem <<= 1;
> }
> }
> - n_rem >>= 12;
> - prom[0] = crc_read;
>
> - return n_rem == crc;
> + return n_rem >> 12;
> +}
> +
> +/**
> + * ms_sensors_tp_crc_valid_112() - CRC check function for
> + * Temperature and pressure devices for 112bit PROM.
> + * This function is only used when reading PROM coefficients
> + *
> + * @prom: pointer to PROM coefficients array
> + *
> + * Return: CRC.

That's a bit confusing. Perhaps return if CRC correct
Sometimes CRC is used to refer to particular bits and sometimes
to the check (i.e. whether it is right).

> + */
> +static bool ms_sensors_tp_crc_valid_112(u16 *prom)
> +{
> + u16 w0 = prom[0], crc_read = (w0 & 0xF000) >> 12;
> + u8 crc;
> +
> + prom[0] &= 0x0FFF; /* Clear the CRC computation part */
> + prom[MS_SENSORS_TP_PROM_WORDS_NB - 1] = 0;
> +
> + crc = ms_sensors_tp_crc4(prom);
> +
> + prom[0] = w0;
> +
> + return crc == crc_read;
> +}
> +
> +/**
> + * ms_sensors_tp_crc_valid_128() - CRC check function for
> + * Temperature and pressure devices for 128bit PROM.
> + * This function is only used when reading PROM coefficients
> + *
> + * @prom: pointer to PROM coefficients array
> + *
> + * Return: CRC.
> + */
> +static bool ms_sensors_tp_crc_valid_128(u16 *prom)
> +{
> + u16 w7 = prom[7], crc_read = w7 & 0x000F;
> + u8 crc;
> +
> + prom[7] &= 0xFF00; /* Clear the CRC and LSB part */
> +
> + crc = ms_sensors_tp_crc4(prom);
> +
> + prom[7] = w7;
> +
> + return crc == crc_read;
> }
>
> /**
> @@ -535,6 +577,7 @@ static bool ms_sensors_tp_crc_valid(u16 *prom)
> int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
> {
> int i, ret;
> + bool valid;
>
> for (i = 0; i < dev_data->hw->prom_len; i++) {
> ret = ms_sensors_read_prom_word(
> @@ -546,7 +589,12 @@ int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
> return ret;
> }
>
> - if (!ms_sensors_tp_crc_valid(dev_data->prom)) {
> + if (dev_data->hw->prom_len == 8)
> + valid = ms_sensors_tp_crc_valid_128(dev_data->prom);
> + else
> + valid = ms_sensors_tp_crc_valid_112(dev_data->prom);
> +
> + if (!valid) {
> dev_err(&dev_data->client->dev,
> "Calibration coefficients crc check error\n");
> return -ENODEV;