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Date:   Wed, 29 Jun 2022 12:05:23 -0700
From:   Kalesh Singh <kaleshsingh@google.com>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        Christian Brauner <brauner@kernel.org>,
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        Jakub Kicinski <kuba@kernel.org>,
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Subject: Re: [PATCH] remove CONFIG_ANDROID
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On Wed, Jun 29, 2022 at 07:34:58PM +0200, Jason A. Donenfeld wrote:
> On Wed, Jun 29, 2022 at 06:38:09PM +0200, Jason A. Donenfeld wrote:
> > On the technical topic, an Android developer friend following this
> > thread just pointed out to me that Android doesn't use PM_AUTOSLEEP and
> > just has userspace causing suspend frequently. So by his rough
> > estimation your patch actually *will* break Android devices. Zoinks.
> > Maybe he's right, maybe he's not -- I don't know -- but you should
> > probably look into this if you want this patch to land without breakage.
> 
> More details: https://cs.android.com/android/platform/superproject/+/master:system/core/libsuspend/autosuspend_wakeup_count.cpp;bpv=1;bpt=1;l=52?q=%22%2Fsys%2Fpower%2Fstate%22&start=51&gsn=sys_power_state&gs=kythe%3A%2F%2Fandroid.googlesource.com%2Fplatform%2Fsuperproject%3Flang%3Dc%252B%252B%3Fpath%3Dsystem%2Fcore%2Flibsuspend%2Fautosuspend_wakeup_count.cpp%23ftWlDJuOhS_2fn3Ri7rClxA30blj_idGgT12aoUHd1o
> 
> So indeed it looks like it's userspace controlled. If you want this to
> be a runtime, rather than a compiletime, switch, maybe
> autosuspend_init() of that file could write to a sysctl.
> 
> Who at Google "owns" that code? Can somebody CC them in?

Hi Jason,

Thanks for raising this.

Android no longer uses PM_AUTOSLEEP, is correct. libsuspend is
also now deprecated. Android autosuspend is initiatiated from the
userspace system suspend service [1].

A runtime config sounds more reasonable since in the !PM_AUTOSLEEP
case, it is userspace which decides the suspend policy.

[1] https://cs.android.com/android/platform/superproject/+/bf3906ecb33c98ff8edd96c852b884dbccb73295:system/hardware/interfaces/suspend/1.0/default/SystemSuspend.cpp;l=265

--Kalesh

> 
> Jason
>