On Tue, Aug 09, 2022 at 04:50:20PM PDT, Zoltán Kővágó wrote:
On 2022-08-10 00:34, Zev Weiss wrote:
On Tue, Aug 09, 2022 at 02:28:20PM PDT, Zoltán Kővágó wrote:
On 2022-08-09 22:56, Zev Weiss wrote:
On Tue, Aug 09, 2022 at 01:27:48PM PDT, Zoltán Kővágó wrote:
Hi,
[1.] One line summary of the problem:
NCT6775: suspend doesn't work after updating to Linux 5.19
[2.] Full description of the problem/report:
After updating my kernel from 5.18.11 to 5.19, I've noticed
that resuming after suspend no longer works: fans start up,
then about a second later, the computer just shuts down,
leaving the USB ports powered up (normally it turns them off
on shutdown). The screens don't turn on during this timeframe,
so I can't see any useful log messages.
Bisecting between 5.18 (where it still worked) and 5.19 lead
me to commit c3963bc0a0cf9ecb205a9d4976eb92b6df2fa3fd "hwmon:
(nct6775) Split core and platform driver" which looks like a
refactor commit, but apparently it broke something.
Hi Zoltán,
Thanks for the thorough bug report. You're right that that
commit was essentially just a refactor, though there was one
slight change to the nct6775_suspend() function introduced
during the review process that may perhaps have had some subtle
unintended side-effects.
Can you test the following patch and report if it resolves the problem?
Thanks,
Zev
Hi Zev,
Thanks for the quick reply. Yes, it looks like your patch does
solve the problem (I've applied it on top of 5.19 (after fighting
with my mail client for a while) and suspended a few times, it's
working so far).
Regards,
Zoltan
Great, thanks.
Guenter, it looks like nct6775_suspend() really does in fact need to
use nct6775_update_device() instead of dev_get_drvdata(), though
it's not immediately obvious to me why. Though given that the bulk
of of the body of nct6775_update_device() is inside an 'if' block
that might not necessarily execute every time, I also wonder if it
might be vulnerable to exhibiting the same problem depending on
timing.
Zoltán, if you could try another experiment to try to gather some
data on that -- with the patch from my previous email still applied,
could you try suspending via:
$ cat
/sys/bus/platform/drivers/nct6775/nct6775.*/hwmon/hwmon*/*_input &&
echo mem > /sys/power/state
Tried it, three times in fact, and it worked fine every time. Looking
at the dmesg, though, it looks like it needs a bit more than 1.5 sec
to suspend. Where's that 1.5 sec limit defined? I will try to increase
it tomorrow.
The 1.5 second duration comes from this line in nct6775_update_device():
if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
Each 'HZ' represents one second, so HZ + HZ / 2 = 1.5 sec; if you want
to lengthen it you could do e.g. 10 * HZ or something instead.
Though as Guenter noted, one other possibility is that with the previous
(buggy) version nct6775_update_device() might never have gotten called
at all -- do you know if that might be the case on your system? (i.e.
do you have any userspace monitoring program or the like that would have
been reading from the nct6775 device's sensors?) If something like that
never ran between the driver getting loaded and the system suspending,
that might also (partially) explain things; to test that out you could
revert to the old buggy code and see if the suspend problem still occurs
if you explicitly run
$ cat /sys/bus/platform/drivers/nct6775/nct6775.*/hwmon/hwmon*/*_input
(or just 'sensors' if you've got the lm-sensors package installed). That will
ensure that nct6775_update_device() gets called before the suspend
operation, which could help narrow things down further.
Thanks,
Zev
