On Wed, Aug 23, 2017 at 9:34 PM, Pavel Machek [off-list ref] wrote:

quoted

On Tue, Jun 13, 2017 at 4:39 AM, Zhang Bo [off-list ref] wrote:

quoted

This reverts commit 5ab92a7cb82c66bf30685583a38a18538e3807db.

System cannot enter suspend mode because of heartbeat led trigger.
In autosleep_wq, try_to_suspend function will try to enter suspend
mode in specific period. it will get wakeup_count then call pm_notifier
chain callback function and freeze processes.
Heartbeat_pm_notifier is called and it call led_trigger_unregister to
change the trigger of led device to none. It will send uevent message
and the wakeup source count changed. As wakeup_count changed, suspend
will abort.

Signed-off-by: Zhang Bo <redacted>

While investigating an heartbeat LED issue in v4.9.40-ltsi, I stumpled on this
revert (commit 436c4c45b5b9562b ("Revert "leds: handle suspend/resume in
heartbeat trigger"") in v4.12-rc6), which was not backported to v4.9 (yet).

Interestingly, while running v4.9.x on r8a7791/koelsch with an LED configured
for heartbeat, I can actually suspend the system using s2ram.
However, after system resume the heartbeat LED no longer flashes.
/sys/class/leds/LED6/trigger shows the trigger is still "none", and thus
wasn't restored to "heartbeat" by the notifier.
There's no "could not re-register heartbeat trigger" message printed.

Backporting the revert fixes this.

You have my Acked-by: if you want to submit this to some -stable
kernels...

Thank you!

Greg: Can you please queue 436c4c45b5b9562b ("Revert "leds: handle
suspend/resume in heartbeat trigger"") for v4.9.x or v4.9-ltsi?
Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds