Re: SDIO driver return -ENOSYS behaviour change?

[Aaron Lu <aaron.lu@intel.com>]

On 02/28/2014 04:30 PM, Ulf Hansson wrote:
> On 28 February 2014 03:37, Aaron Lu <aaron.lu@intel.com> wrote:
>> On 02/27/2014 09:05 PM, Ulf Hansson wrote:
>>> I think it's more a matter of having a controlled suspend sequence.
>>> The mmc core are not able to serve any new SDIO requests while it is
>>> suspended, therefore it tells the sdio func driver about when it safe
>>> to send request - using it's PM callbacks.
>>
>> Does this mean after the function device is suspended from PM core's
>> pespective, the mmc core will still send some requests to the function
>> device? I did see one such request, disable_width, get sent after the
>> function driver's suspend callback is invoked, don't know if there are
>> others.
> 
> Nope. The mmc core will send request to the "card device" during
> suspend. Those are part's of a sequence to put the card in a proper
> "suspend mode".

I suppose this request is sent after calling function driver's suspend
callback? BTW, what request is it?

> 
>>
>> From the mmc_sdio_suspend function I can see two things are done:
>> 1 function device driver's suspend callback is called;
>> 2 optionally disable_width and power off the card according to some flags.
>>
>> So once we fixed the -ENOSYS problem, can we have the function device
>> run its own suspend callback and have the mmc_sdio_suspend just did the
>> disable_width and power off thing?
> 
> That requires that all sdio func devices get suspended before the card
> devices. (And resumed after, but that will of course be implicit.)

Yes, and this is guaranteed by PM core as the function device is the
child of the card device.

> 
> I guess the guarantee for that is already present, since we have added
> the func device to the driver model after we have added the card
> device at mmc_sdio_attach(). So, I suppose this could work.

Exactly.

> 
> Do you want me to create a patch that you can test?

That would be good. I do not have any SDIO card at hand, but I would be
glad to review the patch.

Thanks,
Aaron