On Thu, May 23, 2024 at 03:10:56PM +0300, Radu Sabau wrote:
> Add support for PEC by attaching PEC attribute to the i2c device.
> Add pec_store and pec_show function for accesing the "pec" file.
>
> Signed-off-by: Radu Sabau <radu.sabau@xxxxxxxxxx>
> ---
Change log missing.
> Documentation/hwmon/max31827.rst | 13 +++++--
> drivers/hwmon/max31827.c | 64 ++++++++++++++++++++++++++++++++
> 2 files changed, 74 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
> index 44ab9dc064cb..9c11a9518c67 100644
> --- a/Documentation/hwmon/max31827.rst
> +++ b/Documentation/hwmon/max31827.rst
> @@ -131,7 +131,14 @@ The Fault Queue bits select how many consecutive temperature faults must occur
> before overtemperature or undertemperature faults are indicated in the
> corresponding status bits.
>
> -Notes
> ------
> +PEC Support
> +-----------
> +
> +When reading a register value, the PEC byte is computed and sent by the chip.
> +
> +PEC on word data transaction respresents a signifcant increase in bandwitdh
> +usage (+33% for both write and reads) in normal conditions.
>
> -PEC is not implemented.
> +Since this operation implies there will be an extra delay to each
> +transaction, PEC can be disabled or enabled through sysfs.
> +Just write 1 to the "pec" file for enabling PEC and 0 for disabling it.
> diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
> index f8a13b30f100..e86f8890ee72 100644
> --- a/drivers/hwmon/max31827.c
> +++ b/drivers/hwmon/max31827.c
> @@ -24,6 +24,7 @@
>
> #define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0)
> #define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1)
> +#define MAX31827_CONFIGURATION_PEC_EN_MASK BIT(4)
> #define MAX31827_CONFIGURATION_TIMEOUT_MASK BIT(5)
> #define MAX31827_CONFIGURATION_RESOLUTION_MASK GENMASK(7, 6)
> #define MAX31827_CONFIGURATION_ALRM_POL_MASK BIT(8)
> @@ -475,6 +476,54 @@ static ssize_t temp1_resolution_store(struct device *dev,
>
> static DEVICE_ATTR_RW(temp1_resolution);
>
> +static ssize_t pec_show(struct device *dev, struct device_attribute *devattr,
> + char *buf)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> +
> + return scnprintf(buf, PAGE_SIZE, "%d\n", !!(client->flags & I2C_CLIENT_PEC));
> +}
> +
> +static ssize_t pec_store(struct device *dev, struct device_attribute *devattr,
> + const char *buf, size_t count)
> +{
> + struct max31827_state *st = dev_get_drvdata(dev);
> + struct i2c_client *client = to_i2c_client(dev);
> + unsigned int val;
> + int err;
> +
> + err = kstrtouint(buf, 10, &val);
> + if (err < 0)
> + return err;
> +
> + switch (val) {
> + case 0:
> + err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> + MAX31827_CONFIGURATION_PEC_EN_MASK,
> + val);
While correct, this is misleading. Should write 0.
> + if (err)
> + return err;
> +
> + client->flags &= ~I2C_CLIENT_PEC;
> + break;
> + case 1:
> + err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> + MAX31827_CONFIGURATION_PEC_EN_MASK,
> + val);
This is wrong. s/val/MAX31827_CONFIGURATION_PEC_EN_MASK/
Guenter
