Commit dca5480a authored Apr 27, 2023 by Stefan Wahren Committed by Krzysztof Kozlowski May 08, 2023

w1: w1_therm: fix locking behavior in convert_t

The commit 67b392f7 ("w1_therm: optimizing temperature read timings")
accidentially inverted the logic for lock handling of the bus mutex.

Before:
  pullup -> release lock before sleep
  no pullup -> release lock after sleep

After:
  pullup -> release lock after sleep
  no pullup -> release lock before sleep

This cause spurious measurements of 85 degree (powerup value) on the
Tarragon board with connected 1-w temperature sensor
(w1_therm.w1_strong_pull=0).

In the meantime a new feature for polling the conversion
completion has been integrated in these branches with
commit 021da53e ("w1: w1_therm: Add sysfs entries to control
conversion time and driver features"). But this feature isn't
available for parasite power mode, so handle this separately.

Link: https://lore.kernel.org/regressions/2023042645-attentive-amends-7b0b@gregkh/T/


Fixes: 67b392f7 ("w1_therm: optimizing temperature read timings")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/20230427112152.12313-1-stefan.wahren@i2se.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

parent ac9a7868

drivers/w1/slaves/w1_therm.c

+14 −17

Original line number	Diff line number	Diff line
		@@ -1159,14 +1159,6 @@ static int convert_t(struct w1_slave sl, struct therm_info info)

		w1_write_8(dev_master, W1_CONVERT_TEMP);

		if (strong_pullup) { /some device need pullup /
		sleep_rem = msleep_interruptible(t_conv);
		if (sleep_rem != 0) {
		ret = -EINTR;
		goto mt_unlock;
		}
		mutex_unlock(&dev_master->bus_mutex);
		} else { /no device need pullup /
		if (SLAVE_FEATURES(sl) & W1_THERM_POLL_COMPLETION) {
		ret = w1_poll_completion(dev_master, W1_POLL_CONVERT_TEMP);
		if (ret) {
		@@ -1174,8 +1166,14 @@ static int convert_t(struct w1_slave sl, struct therm_info info)
		goto mt_unlock;
		}
		mutex_unlock(&dev_master->bus_mutex);
		} else {
		/* Fixed delay */
		} else if (!strong_pullup) { /no device need pullup /
		sleep_rem = msleep_interruptible(t_conv);
		if (sleep_rem != 0) {
		ret = -EINTR;
		goto mt_unlock;
		}
		mutex_unlock(&dev_master->bus_mutex);
		} else { /some device need pullup /
		mutex_unlock(&dev_master->bus_mutex);
		sleep_rem = msleep_interruptible(t_conv);
		if (sleep_rem != 0) {
		@@ -1183,7 +1181,6 @@ static int convert_t(struct w1_slave sl, struct therm_info info)
		goto dec_refcnt;
		}
		}
		}
		ret = read_scratchpad(sl, info);

		/* If enabled, check for conversion success */