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Date:   Tue, 10 Aug 2021 17:06:05 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Prasad Sodagudi <psodagud@codeaurora.org>
Cc:     rjw@rjwysocki.net, len.brown@intel.com,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        pavel@ucw.cz
Subject: Re: [PATCH v2] PM: sleep: core: Avoid setting power.must_resume to
 false
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On Tue, Aug 10, 2021 at 06:42:11AM -0700, Prasad Sodagudi wrote:
> This is regarding suspend/resume(s2idle) scenario of devices and difference
> between the LTS kernels 5.4 and 5.10 with respect to devices suspend and
> resume. Observing that devices suspended in suspend_late stage are not
> getting resumed in resume_early stage.
> 1) LTS kernel 5.4 kernel do not have this problem but 5.10 kernel
> shows this problem.
> 2) 'commit 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase")'
> is skipping the driver early_resume callbacks.
> 
> In device_resume_early function dev->power.must_resume is used to skip the
> resume call back. It looks this function is expecting that,
> __device_suspend_noirq() would set dev->power.must_resume = true for the
> devices which does not have DPM_FLAG_MAY_SKIP_RESUME flag set.
> 
> 3) Problematic scenario is as follows -  During the device suspend/resume
> scenario all the devices in  the suspend_late stage are successful and some
> device can fail to suspend in suspend_noirq(device_suspend_noirq->
> __device_suspend_noirq) phase.
> As a device failed in dpm_noirq_suspend_devices phase, dpm_resume_noirq is
> getting called to resume devices in dpm_late_early_list in the noirq phase.
> 
> 4) During the Devices_early_resume stage
> dpm_resume_early()-->device_resume_early() functions skipping the devices
> early resume callbacks.
> 799         if (dev_pm_skip_resume(dev))
> 800                  goto Skip;
> 
> 5) Devices suspended in suspend_late stage are not getting resumed in
> Devices_early_resume stage because of
> 'commit 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase")'
> is skipping the driver early_resume callbacks when dev->power.must_resume is false.
> 
> 
> Changelog:
> v1 -> v2:
>  - Fixed indentation comments.
>  - Commit text updated to include scenario.
> 
> Prasad Sodagudi (1):
>   PM: sleep: core: Avoid setting power.must_resume to false
> 
>  drivers/base/power/main.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

I do not see a patch here, what happened?

:(