On Wed, Aug 10, 2022 at 01:22:04AM PDT, Zoltán Kővágó wrote:
On 2022-08-10 03:39, Zev Weiss wrote:
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.
Tried that, this isn't the problem.
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.
Yup, this was it. It looks like I remembered it wrong and my
monitoring widget in the end only used k10temp and not nct6798, so I
could very easily suspend without any reads from nct6775 before (and
that widget itself even only ran when I had an X session).
Regards,
Zoltan
Great, glad that's confirmed. The fix is now in Linus's tree and should
presumably get picked up in the -stable tree for 5.19.1.
Thanks for the bug report & testing!
Zev
