From 7cd60538073e465310c94b2a2f0ea8d2f03768ef Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Fri, 30 Oct 2026 20:02:08 -0700 Subject: [PATCH] hwmon: (tmp108) Fix initial conversion delay and wait until ready MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In tmp108_common_probe(), the driver only adds the 30 ms conversion delay (TMP108_CONVERSION_TIME_MS) to ready_time if the sensor was previously in TMP108_MODE_SHUTDOWN. However, the TMP108 hardware defaults to continuous conversion mode (TMP108_MODE_CONTINUOUS) upon power-on reset, including immediately after enabling the vcc supply regulator during probe, while the temperature register retains its power-on reset value of 0x0000 (0°C) until the first conversion completes. Because the initial mode is not shutdown, the delay is bypassed and early reads via thermal zone registration or sysfs before the first conversion finishes return an uninitialized 0°C reading. In addition, returning -EAGAIN from tmp108_read() while waiting for a conversion to complete after probe or resume can trigger an unnecessary tight retry loop in callers or fail initial reads. Unconditionally set ready_time to TMP108_CONVERSION_TIME_MS ahead in tmp108_common_probe(), track ready_time as ktime_t, and wait for the remaining conversion time in tmp108_read() using usleep_range() instead of returning -EAGAIN. Reported-by: Sashiko Fixes: 66e1c9171339 ("hwmon: Add Texas Instruments TMP108 temperature sensor driver.") Cc: stable@vger.kernel.org Signed-off-by: Guenter Roeck --- drivers/hwmon/tmp108.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/drivers/hwmon/tmp108.c b/drivers/hwmon/tmp108.c index 91d20a1ce112..862b944d3e60 100644 --- a/drivers/hwmon/tmp108.c +++ b/drivers/hwmon/tmp108.c @@ -13,7 +13,7 @@ #include #include #include -#include +#include #include #include #include @@ -78,7 +78,7 @@ struct tmp108 { struct regmap *regmap; u16 orig_config; - u64 ready_time; + ktime_t ready_time; const struct tmp108_params *params; }; @@ -121,6 +121,7 @@ static int tmp108_read(struct device *dev, enum hwmon_sensor_types type, struct tmp108 *tmp108 = dev_get_drvdata(dev); unsigned int regval; int err, hyst; + s64 delay; if (type == hwmon_chip) { if (attr == hwmon_chip_update_interval) { @@ -137,12 +138,10 @@ static int tmp108_read(struct device *dev, enum hwmon_sensor_types type, switch (attr) { case hwmon_temp_input: - /* Is it too early to return a conversion ? */ - if (time_before64(get_jiffies_64(), tmp108->ready_time)) { - dev_dbg(dev, "%s: Conversion not ready yet..\n", - __func__); - return -EAGAIN; - } + /* Wait if it is too early to return a conversion */ + delay = ktime_us_delta(tmp108->ready_time, ktime_get()); + if (delay > 0) + usleep_range(delay, delay + 1000); err = regmap_read(tmp108->regmap, TMP108_REG_TEMP, ®val); if (err < 0) return err; @@ -477,11 +476,8 @@ static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char * return err; } - tmp108->ready_time = get_jiffies_64(); - if ((tmp108->orig_config & TMP108_CONF_MODE_MASK) == - TMP108_MODE_SHUTDOWN) - tmp108->ready_time += - msecs_to_jiffies(TMP108_CONVERSION_TIME_MS); + tmp108->ready_time = ktime_add_ms(ktime_get(), + TMP108_CONVERSION_TIME_MS); err = devm_add_action_or_reset(dev, tmp108_restore_config, tmp108); if (err) { @@ -528,8 +524,8 @@ static int tmp108_resume(struct device *dev) err = regmap_update_bits(tmp108->regmap, TMP108_REG_CONF, TMP108_CONF_MODE_MASK, TMP108_MODE_CONTINUOUS); - tmp108->ready_time = get_jiffies_64() + - msecs_to_jiffies(TMP108_CONVERSION_TIME_MS); + tmp108->ready_time = ktime_add_ms(ktime_get(), + TMP108_CONVERSION_TIME_MS); return err; }