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authorDavid Mosberger-Tang <davidm@egauge.net>2021-11-20 21:28:56 +0000
committerGuenter Roeck <linux@roeck-us.net>2021-11-20 14:44:25 -0800
commit0e4190d762ef2609111507e1b9553a166436f556 (patch)
treed2d522ef5f68aca3debc672842850333a492a0c5 /drivers/hwmon
parent214f525255069a55b4664842c68bc15b2ee049f0 (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')
-rw-r--r--drivers/hwmon/sht4x.c4
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) {