diff options
| author | David Mosberger-Tang <davidm@egauge.net> | 2021-11-20 21:28:56 +0000 |
|---|---|---|
| committer | Guenter Roeck <linux@roeck-us.net> | 2021-11-20 14:44:25 -0800 |
| commit | 0e4190d762ef2609111507e1b9553a166436f556 (patch) | |
| tree | d2d522ef5f68aca3debc672842850333a492a0c5 /drivers/hwmon/sht4x.c | |
| parent | 214f525255069a55b4664842c68bc15b2ee049f0 (diff) | |
hwmon: (sht4x) Fix EREMOTEIO errors
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@egauge.net>
Link: https://lore.kernel.org/r/20211120212849.2300854-2-davidm@egauge.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Diffstat (limited to 'drivers/hwmon/sht4x.c')
| -rw-r--r-- | drivers/hwmon/sht4x.c | 4 |
1 files 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) { |