linux-kernel - Re: [PATCH] ARM: OMAP2+: omap_device: drop broken RPM status update from suspend

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Message-ID: <20170725071048.GP10026@atomide.com>
Date:   Tue, 25 Jul 2017 00:10:49 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Johan Hovold <johan@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        Dave Gerlach <d-gerlach@...com>,
        Kevin Hilman <khilman@...libre.com>,
        Nishanth Menon <nm@...com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] ARM: OMAP2+: omap_device: drop broken RPM status update
 from suspend_noirq

* Grygorii Strashko <grygorii.strashko@...com> [170724 15:17]:
> My personal thought here is that removing of pm_runtime_set_active() will not fix
> root cause of the problem, but rather hide it :( and, probably, real fix will be 
> to update USB framework to ensure that all suspend devices are also PM runtime suspend
> (not sure how) or add few more pm_suspend_ignore_children() calls 
>  (for example as I've tried to do in [2], but this was unfinished).
> 
> I've found very simple steps to reproduce suspend failure on am335x-evm (should also
> work on BBB) -  do below sequence with USB device plugged:
> 
>    echo platform > /sys/power/pm_test 
>    echo 1 > /sys/power/pm_print_times 
>    [ echo 0 > /sys/module/printk/parameters/console_suspend ]
>    echo mem > /sys/power/state 
> 
> [   95.499685] calling  47400000.usb+ @ 733, parent: ocp
> [   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
> [   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0
> 
> Below I've attached possible patch which converts OMAP device to
> use pm_runtime_force_suspend/resume().

It seems to almost work for my PM test cases.. It seems that serial console
somehow won't get restored after suspend/resume cycle on omap3 though.

The system enters off mode during suspend, and wakes up properly so I can
ssh to it after resume. But the serial console no longer works after resume.
This is with 8250-omap driver.

Regards,

Tony