[PATCH v2] ath10k: add SoC power save option to PCI features map

[Michal Kazior]

On 5 August 2013 18:40, Kalle Valo <kvalo at qca.qualcomm.com> wrote:
> Michal Kazior <michal.kazior at tieto.com> writes:
>
>> On 2 August 2013 09:58, Bartosz Markowski <bartosz.markowski at tieto.com> wrote:
>>> Unify the PCI options location.
>>>
>>> By default the SoC PS option is disabled to boost the
>>> performance and due to poor stability on early HW revisions.
>>> In future we can remove the module parameter and turn on/off
>>> the PS for given hardware.
>>>
>>> This change also makes the pci module parameter for SoC PS static.
>>>
>>> Signed-off-by: Bartosz Markowski <bartosz.markowski at tieto.com>
>>
>> Hmm.. I'm worried about pci wake/sleep locking:
>>
>>  (a) pci_wake() (awake count =1)
>>  (a) do something
>>  Now, if pci_sleep() and pci_wake() happen simultaneously/are
>> preempted splitting primitive operations to:
>>  (a) pci_sleep(): decrease awake count (=0)
>>  (b) pci_wake(): increase awake count (=1), iowrite, wait for awake, return
>>  (a) pci_sleep(): iowrite(). return
>>  The flow in (b) now thinks the device is awake, but it's not
>> guaranteed to be anymore because it has been put to sleep by (a).
>
> Yeah, there's a race alright. I wonder if I have ever seen a proper use
> of a atomic variable in a wireless driver :)
>
> But this doesn't prevent taking this patch as the race has existed since
> the beginning, right?

I don't have anything against it. I just noticed the race and thought
it's good to point out the issue.


Pozdrawiam / Best regards,
Michał Kazior.