2023-04-27 11:24:30

by Stefan Wahren

Subject: [PATCH RFC] w1: w1_therm: fix locking behavior in convert_t

The commit 67b392f7b8ed ("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 021da53e65fd ("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: 67b392f7b8ed ("w1_therm: optimizing temperature read timings")
Signed-off-by: Stefan Wahren <[email protected]>
---
drivers/w1/slaves/w1_therm.c | 31 ++++++++++++++-----------------
1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 067692626cf0..99c58bd9d2df 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -1159,29 +1159,26 @@ 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 */
+ if (SLAVE_FEATURES(sl) & W1_THERM_POLL_COMPLETION) {
+ ret = w1_poll_completion(dev_master, W1_POLL_CONVERT_TEMP);
+ if (ret) {
+ dev_dbg(&sl->dev, "%s: Timeout\n", __func__);
+ goto mt_unlock;
+ }
+ mutex_unlock(&dev_master->bus_mutex);
+ } 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 { /*no device need pullup */
- if (SLAVE_FEATURES(sl) & W1_THERM_POLL_COMPLETION) {
- ret = w1_poll_completion(dev_master, W1_POLL_CONVERT_TEMP);
- if (ret) {
- dev_dbg(&sl->dev, "%s: Timeout\n", __func__);
- goto mt_unlock;
- }
- mutex_unlock(&dev_master->bus_mutex);
- } else {
- /* Fixed delay */
- mutex_unlock(&dev_master->bus_mutex);
- sleep_rem = msleep_interruptible(t_conv);
- if (sleep_rem != 0) {
- ret = -EINTR;
- goto dec_refcnt;
- }
+ } else { /*some device need pullup */
+ mutex_unlock(&dev_master->bus_mutex);
+ sleep_rem = msleep_interruptible(t_conv);
+ if (sleep_rem != 0) {
+ ret = -EINTR;
+ goto dec_refcnt;
}
}
ret = read_scratchpad(sl, info);
--
2.34.1

2023-05-08 09:26:59

by Krzysztof Kozlowski

Subject: Re: [PATCH RFC] w1: w1_therm: fix locking behavior in convert_t

On Thu, 27 Apr 2023 13:21:52 +0200, Stefan Wahren wrote:
> The commit 67b392f7b8ed ("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
>
> [...]

Applied, thanks!

[1/1] w1: w1_therm: fix locking behavior in convert_t
https://git.kernel.org/krzk/linux-w1/c/dca5480ab7b77a889088ab7cac81934604510ac7

Best regards,
--
Krzysztof Kozlowski <[email protected]>