From 0e4190d762ef2609111507e1b9553a166436f556 Mon Sep 17 00:00:00 2001 From: David Mosberger-Tang Date: Sat, 20 Nov 2021 21:28:56 +0000 Subject: 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 Link: https://lore.kernel.org/r/20211120212849.2300854-2-davidm@egauge.net Signed-off-by: Guenter Roeck --- drivers/hwmon/sht4x.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/hwmon/sht4x.c') 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) { -- cgit v1.2.3