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Date: Tue, 10 Aug 2021 17:06:05 +0200 From: Greg KH <gregkh@...uxfoundation.org> To: Prasad Sodagudi <psodagud@...eaurora.org> Cc: rjw@...ysocki.net, len.brown@...el.com, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, pavel@....cz Subject: Re: [PATCH v2] PM: sleep: core: Avoid setting power.must_resume to false 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? :(
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