Re: [RESEND/PATCH] i2c: pxa: Use suspend() and resume() instead of the _noirq hooks
> suspend/resume order depends on probe ordering, so with deferred probe, > the probe ordering might be right, but it should be thoroughly tested. Thanks a lot for the input here, Kevin! signature.asc Description: Digital signature
Re: [RESEND/PATCH] i2c: pxa: Use suspend() and resume() instead of the _noirq hooks
Ezequiel Garcia writes:
> On 10/20/2014 06:07 PM, Kevin Hilman wrote:
>> Ezequiel Garcia 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
>>> 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.
Good. :)
>> 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.
Correct.
> 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.
That's right. That's why many i2c drivers are using the late/early
callbacks for suspend/resume.
suspend/resume order depends on probe ordering, so with deferred probe,
the probe ordering might be right, but it should be thoroughly tested.
Kevin
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Re: [RESEND/PATCH] i2c: pxa: Use suspend() and resume() instead of the _noirq hooks
On 10/20/2014 06:07 PM, Kevin Hilman wrote:
> Ezequiel Garcia 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
>> 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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Description: OpenPGP digital signature
Re: [RESEND/PATCH] i2c: pxa: Use suspend() and resume() instead of the _noirq hooks
Ezequiel Garcia 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
> 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?
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.
Kevin
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