linux-kernel - Re: [PATCH] i2c: designware: Fix unbalanced suspended flag

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Date:   Fri, 9 Dec 2022 14:22:14 +0000
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     Hans de Goede <hdegoede@...hat.com>, <wsa@...nel.org>,
        <jarkko.nikula@...ux.intel.com>,
        <andriy.shevchenko@...ux.intel.com>,
        <mika.westerberg@...ux.intel.com>, <jsd@...ihalf.com>
CC:     <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>
Subject: Re: [PATCH] i2c: designware: Fix unbalanced suspended flag

On 9/12/22 13:36, Richard Fitzgerald wrote:
> On 9/12/22 12:15, Hans de Goede wrote:
>> Hi Richard,
>>
>> On 12/9/22 12:40, Richard Fitzgerald wrote:
>>> Ensure that i2c_mark_adapter_suspended() is always balanced by a call to
>>> i2c_mark_adapter_resumed().
> 
> <snip>
> 
>>
>> It is not entirely clear to me where the unbalance you claim to see comes
>> from? When runtime-suspended SMART_SUSPEND should keep it suspended at 
>> which point
>> the system suspend callback will never run ?
>>
>> Are you sure that you are not maybe seeing a suspend/resume ordering 
>> issue?
>>
>> Did you add printk messages to the suspend/resume callbacks of
>> i2c-designware-platdrv.c which show the system suspend callback
>> being called but not the system resume one ?
>>
> 
> With messages in strategic places.
> 
> [  169.607358] i2c_designware i2c_designware.2: PM: dev_pm_skip_suspend: 
> SMART_SUSPEND=0 pm_runtime_status_suspended=1
> [  169.607361] i2c_designware i2c_designware.2: PM: 
> __device_suspend_late: dev_pm_skip_suspend:false
> [  169.607364] i2c_designware i2c_designware.2: dw_i2c_plat_suspend
> ...
> [  169.702511] i2c_designware i2c_designware.2: PM: dev_pm_skip_resume: 
> 1 because !power.must_resume
> [  169.706241] i2c_designware i2c_designware.2: PM: dev_pm_skip_resume: 
> 1 because !power.must_resume
> [  169.706244] i2c_designware i2c_designware.2: PM: device_resume_early: 
> dev_pm_skip_resume:true
> ...
> [  175.254832] i2c i2c-2: Transfer while suspended
> 
> (Just to prove my logging isn't lying, for i2c3 it reports
> SMART_SUSPEND=1)
> 

Oh, that's embarrassing. After confidently telling you my logging
is perfect, actually there was a bug in it...

New log summary:

[  162.253431] i2c_designware i2c_designware.2: PM: dev_pm_skip_suspend: 
SMART_SUSPEND=1 pm_runtime_status_suspended=0
[  162.253438] i2c_designware i2c_designware.2: PM: 
__device_suspend_late: dev_pm_skip_suspend:false
[  162.253445] i2c_designware i2c_designware.2: dw_i2c_plat_suspend
[  162.273115] i2c_designware i2c_designware.2: PM: dev_pm_skip_suspend: 
SMART_SUSPEND=1 pm_runtime_status_suspended=0
[  162.362547] i2c_designware i2c_designware.2: PM: dev_pm_skip_resume: 
1 because !power.must_resume
[  162.369216] i2c_designware i2c_designware.2: PM: dev_pm_skip_resume: 
1 because !power.must_resume
[  162.369220] i2c_designware i2c_designware.2: PM: device_resume_early: 
dev_pm_skip_resume:true
[  167.901269] i2c i2c-2: Transfer while suspended

Same result that it doesn't skip suspend but does skip resume.