On 10/20/2014 06:07 PM, Kevin Hilman wrote:
> Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> writes:
>
>> The _noirq were previously chosen to make sure all the users of the
>> adapter were suspended by the time the adapter itself enters the
>> suspended state.
>>
>> The {suspend,resume}_noirq usage was converted from an earlier
>> implementation based on suspend_late and resume_early on this commit:
>>
>> commit 57f4d4f1b72983f8c76e2f232e064730aeffe599
>> Author: Magnus Damm <damm@xxxxxxxxxx>
>> Date: Wed Jul 8 13:22:39 2009 +0200
>>
>> I2C: Rework i2c-pxa suspend_late()/resume_early()
>>
>> However, all the I2C devices are probed as children of its I2C adapter,
>> and hence the device model guarantees they are suspended before its parent, and
>> resumed after it.
>>
>> In other words, there's no need to use the _noirq hooks to get a suspend/resume
>> device/adapter order.
>
> Are you sure *really* about this?
>
Hm, now you made me doubt.
> It's usally not the children that are the problem here. It's usually
> some other driver trying to use an I2C device e.g. MMC changing voltage
> using an I2C-based PMIC during its suspend process.
>
So we can't know for sure if using suspend/resume is going to work OK for
a I2C adapter?
There might be some use of it that can't be accurately modeled in the
device model.
I.e., the above example is a dependency of MMC on the I2C being suspended
after him, but right now there's no way to model such relationship.
--
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar
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