linux-kernel - Re: Keyboard lost after exit s2idle on ASUS UX433FN

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Date:   Thu, 16 Aug 2018 16:18:54 +0800
From:   Chris Chiu <chiu@...lessm.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>
Subject: Re: Keyboard lost after exit s2idle on ASUS UX433FN

On Thu, Aug 16, 2018 at 3:26 PM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> On Thu, Aug 16, 2018 at 4:45 AM Chris Chiu <chiu@...lessm.com> wrote:
>>
>> Hi,
>>     We recently hit a weird problem on the ASUS laptop UX433FN with
>> latest Intel Core i7-8565U CPU on kernel 4.18. The keyboard stops
>> functioning after exit s2idle. It stops firing interrupts after resume
>> on any keypress. We thought it should be something wrong with i8042
>> driver or even atkbd driver, so we tried to skip the suspend/resume
>> path of i8042 and input devices but no luck.
>>
>>     Then we tried to hack the s2idle code to fail right before it goes
>> into the idle state to find out which code really cause the keyboard
>> broken. It comes with an interesting finding that if it aborts s2idle
>> before cpuidle_resume() in s2idle_enter(), the keyboard is fine. If it
>> aborts after cpuidle_resume, then the keyboard down. At least it
>> proves that even with dpm_noirq_begin() and
>> dpm_noirq_suspend_devices() executed, the keyboard is still alive.
>> There should be something wrong with the cpuidle.
>>
>>     Going deeper into intel_idle_s2idle() which is invoked by
>> cpuidle_enter_s2idle(), we found that the keyboard interrupt will no
>> longer function after mwait_idle_with_hints() which just simply
>> executing intel monitor and mwait instructions. So I don't know what
>> should be the next step I can take. Can anyone give some pieces of
>> advice?
>
> It may indicate that the deepest C-states used by s2idle simply don't
> work correctly on the affected system.
>
> To verify this, you can try to disable the deepest C-states via sysfs
> using the "disable" attribute under
> /sys/devices/system/cpu/cpuX/cpuidle/stateX/
>
Thanks for the great help. I can have the keyboard work after s2idle with
the following command

echo 1 > /sys/devices/system/cpu/cpuX/cpuidle/state8/disable

cpuX, X can be 0 to 7 on this CPU.
And only state8 disable would work, it fails on state 0~7 disabled.

There're 9 (0-8) states on the cpuidle of this machine. However, I have another
laptop with the same CPU Intel Core i7-8565U which only have 4(0-3) states
under the same '/sys/devices/system/cpu/cpuX/cpuidle/' entry. Sorry that I
don't have enough background knowledge about cpuidle. I thought the #C
state should be depend on CPU, but why the same i7-8565 has different
number of C-states?  And for this case, should I just disable C-8 state or there
should be a generic fix with it?

> Is s2idle the default suspend method on that system?  If so, have you
> checked whether or not suspend-to-RAM works too?
>

Yes, it's default s2idle. If I do 'echo mem > /sys/power/state', the keyboard
would still fail.

> Thanks,
> Rafael