On Wed, Apr 19, 2017 at 8:59 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote:
> On Thu, Mar 30, 2017 at 03:04:44PM +0300, Jarkko Nikula wrote:
>> There is possibility to enter dw_i2c_plat_suspend() callback twice
>> during system suspend under certain cases which is causing here warnings
>> from clk_core_disable() and clk_core_unprepare() as well as accessing the
>> registers that can be power gated.
>>
>> Commit 8503ff166504 ("i2c: designware: Avoid unnecessary resuming during
>> system suspend") implemented a prepare callback that checks for runtime
>> suspended device which allow PM core to set direct_complete flag and
>> skip system suspend and resume callbacks.
>>
>> However it can still happen if nothing resumes the device prior system
>> syspend (e.g. acpi_subsys_suspend()) and there is a slave device which
>> unsets the direct_complete flag of the parent in __device_suspend() thus
>> causing PM code to not skip the system suspend/resume callbacks.
>>
>> Avoid this by checking runtime status in suspend and resume callbacks
>> and return directly if device is runtime suspended. This affects only
>> system suspend/resume since during runtime suspend/resume runtime status
>> is suspending (not suspended) or resuming.
>>
>> Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
>> ---
>> I'm able to trigger system suspend callback while device is runtime
>> suspended by removing the pm_runtime_resume() call from
>> drivers/mfd/intel-lpss.c: resume_lpss_device() and having unbound I2C
>> slave (ACPI enumerated but doesn't bind due an error in probe function).
>> In that case __device_suspend() for that unbound device has NULL suspend
>> callback, and thus doesn't cause any runtime resume chain but still unsets
>> the parent's direct_complete flag.
>> John Stult <john.stultz@xxxxxxxxxx> has reported he can trigger this on
>> HiKey board too.
>>
>> I'm not sure is this the right thing to do. It feels something the PM core
>> should do but I'm not sure that either. One alternative could be to resume
>> runtime suspended parent in in __device_suspend() right after where
>> parent's direct_complete flag is unset.
>
> Because of the last paragraph, I'd like a positive comment or tag from
> one of the PM people before I apply this one.
No, sorry.
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