Re: [PATCH v3] hwmon: (sht4x) Fix EREMOTEIO errors

[Guenter Roeck]

On Sat, Nov 20, 2021 at 09:28:56PM +0000, David Mosberger-Tang wrote:
> Per datasheet, SHT4x may need up to 8.2ms for a "high repeatability"
> measurement to complete.  Attempting to read the result too early
> triggers a NAK which then causes an EREMOTEIO error.
> 
> This behavior has been confirmed with a logic analyzer while running
> the I2C bus at only 40kHz.  The low frequency precludes any
> signal-integrity issues, which was also confirmed by the absence of
> any CRC8 errors.  In this configuration, a NAK occurred on any read
> that followed the measurement command within less than 8.2ms.
> 
> Signed-off-by: David Mosberger-Tang <davidm@xxxxxxxxxx>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/sht4x.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
> index 09c2a0b06444..3415d7a0e0fc 100644
> --- a/drivers/hwmon/sht4x.c
> +++ b/drivers/hwmon/sht4x.c
> @@ -23,7 +23,7 @@
>  /*
>   * I2C command delays (in microseconds)
>   */
> -#define SHT4X_MEAS_DELAY	1000
> +#define SHT4X_MEAS_DELAY_HPM	8200	/* see t_MEAS,h in datasheet */
>  #define SHT4X_DELAY_EXTRA	10000
>  
>  /*
> @@ -90,7 +90,7 @@ static int sht4x_read_values(struct sht4x_data *data)
>  	if (ret < 0)
>  		goto unlock;
>  
> -	usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> +	usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA);
>  
>  	ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
>  	if (ret != SHT4X_RESPONSE_LENGTH) {