SDIO driver return -ENOSYS behaviour change?

SDIO driver return -ENOSYS behaviour change?

[Aaron Lu]

Hi Ulf,

I was tracking some SDIO suspend problem and came across this. As Neil
mentioned here:
http://lkml.org/lkml/2012/3/25/20
Quote:
"
SDIO (and possible MMC in general) has a protocol where the suspend
 method can return -ENOSYS and this means "There is no point in suspending,
 just turn me off".
"

It seems that the following commit:

commit 810caddba42a54fe5db4e2664757a9a334ba359c
Author: Ulf Hansson <ulf.hansson@linaro.org>
Date:   Mon Jun 10 17:03:37 2013 +0200

    mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE

Changed this behaviour?

For example, the libertas SDIO driver's suspend callback still returns
-ENOSYS and before this commit, that error code will result in the SDIO
device being removed; after this commit, that would result in an error
code returned to PM core and a failure in system suspend.

I'm not sure if I understand this correctly as I do not have any SDIO
card to test. Can you please take a look at this? If this is indeed the
case, do we need to maintain this behaviour? I need to know this answer
as that would affect the way I'm going to solve my problem. Thanks.

Re: SDIO driver return -ENOSYS behaviour change?

[Ulf Hansson]

On 27 February 2014 10:10, Aaron Lu <aaron.lu@intel.com> wrote:
> Hi Ulf,
>
> I was tracking some SDIO suspend problem and came across this. As Neil
> mentioned here:
> http://lkml.org/lkml/2012/3/25/20
> Quote:
> "
> SDIO (and possible MMC in general) has a protocol where the suspend
>  method can return -ENOSYS and this means "There is no point in suspending,
>  just turn me off".
> "
>
> It seems that the following commit:
>
> commit 810caddba42a54fe5db4e2664757a9a334ba359c
> Author: Ulf Hansson <ulf.hansson@linaro.org>
> Date:   Mon Jun 10 17:03:37 2013 +0200
>
>     mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE
>
> Changed this behaviour?

I realized I changed the behaviour to not cover for sdio func drivers,
that actually implements the pm callbacks - but do return -ENOSYS in
them. That wasn't obvious when looking at the code back then, sorry!

There are no solution to this problem in the mmc core right now, since
we can't remove the card while we have reach the state when the
suspend callback is being invoked.

Instead, the sdio func driver shall not implement the PM callbacks at
all. That behaviour means the mmc core will remove the card, but now
it's done a in an earlier phase of the system suspend when we are
still able to remove it.

Kind regards
Uffe

>
> For example, the libertas SDIO driver's suspend callback still returns
> -ENOSYS and before this commit, that error code will result in the SDIO
> device being removed; after this commit, that would result in an error
> code returned to PM core and a failure in system suspend.
>
> I'm not sure if I understand this correctly as I do not have any SDIO
> card to test. Can you please take a look at this? If this is indeed the
> case, do we need to maintain this behaviour? I need to know this answer
> as that would affect the way I'm going to solve my problem. Thanks.

Re: SDIO driver return -ENOSYS behaviour change?

[Aaron Lu]

On 02/27/2014 06:18 PM, Ulf Hansson wrote:
> On 27 February 2014 10:10, Aaron Lu <aaron.lu@intel.com> wrote:
>> Hi Ulf,
>>
>> I was tracking some SDIO suspend problem and came across this. As Neil
>> mentioned here:
>> http://lkml.org/lkml/2012/3/25/20
>> Quote:
>> "
>> SDIO (and possible MMC in general) has a protocol where the suspend
>>  method can return -ENOSYS and this means "There is no point in suspending,
>>  just turn me off".
>> "
>>
>> It seems that the following commit:
>>
>> commit 810caddba42a54fe5db4e2664757a9a334ba359c
>> Author: Ulf Hansson <ulf.hansson@linaro.org>
>> Date:   Mon Jun 10 17:03:37 2013 +0200
>>
>>     mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE
>>
>> Changed this behaviour?
> 
> I realized I changed the behaviour to not cover for sdio func drivers,
> that actually implements the pm callbacks - but do return -ENOSYS in
> them. That wasn't obvious when looking at the code back then, sorry!

Never mind, this behaviour change doesn't cause my problems but knowing
whether this behaviour should be kept affects how I'm going to solve my
problem.

My problem is that, after the following commit:

commit eed222aca8d077af3600b651176f6fd04d95cce1
Author: Aaron Lu <aaron.lu@intel.com>
Date:   Tue Mar 5 11:24:52 2013 +0800

    mmc: sdio: bind acpi with sdio function device

The SDIO function that has an ACPI node associated with will have the
pm_domain assigned, which breaks the intention that during SDIO function
device suspend phase nothing should be done by having a dummy BUS layer
callback. The existence of the pm_domain for the SDIO function device
will make its function driver's suspend callback gets called now. The
end result is the function driver's suspend callback is called twice.

To solve this problem, I was wondering why SDIO function device has this
'special' requirement that nothing should be done at its own device
suspend phase but instead, relies on its suspend callback gets called in
its parent device's suspend callback. And then I realized the reason is
for the special handling of -ENOSYS.

So if we could get rid of the -ENOSYS, my problem could be easily solved
by deleting some lines in current code(the calling of function driver's
suspend callback in mmc_sdio_suspend and the dummy system suspend/resume
callback for SDIO bus). Buf if the behaviour has to be kept, I'll
probably need to remove the pm_domain for the device and do some
additional ACPI handing in mmc_sdio_suspend/resume for the function
device.

> 
> There are no solution to this problem in the mmc core right now, since
> we can't remove the card while we have reach the state when the
> suspend callback is being invoked.
> 
> Instead, the sdio func driver shall not implement the PM callbacks at
> all. That behaviour means the mmc core will remove the card, but now
> it's done a in an earlier phase of the system suspend when we are
> still able to remove it.

The libertas suspend callback is doing different things depending on
different conditions - sometime it will enable wakeup capability and
sometime it will want the mmc core to remove the device entirely by
retuning -ENOSYS, so it may not be that easy by just deleting the
callback, but I don't know for sure.

Thanks,
Aaron

Re: SDIO driver return -ENOSYS behaviour change?

[Ulf Hansson]

On 27 February 2014 12:26, Aaron Lu <aaron.lu@intel.com> wrote:
> On 02/27/2014 06:18 PM, Ulf Hansson wrote:
>> On 27 February 2014 10:10, Aaron Lu <aaron.lu@intel.com> wrote:
>>> Hi Ulf,
>>>
>>> I was tracking some SDIO suspend problem and came across this. As Neil
>>> mentioned here:
>>> http://lkml.org/lkml/2012/3/25/20
>>> Quote:
>>> "
>>> SDIO (and possible MMC in general) has a protocol where the suspend
>>>  method can return -ENOSYS and this means "There is no point in suspending,
>>>  just turn me off".
>>> "
>>>
>>> It seems that the following commit:
>>>
>>> commit 810caddba42a54fe5db4e2664757a9a334ba359c
>>> Author: Ulf Hansson <ulf.hansson@linaro.org>
>>> Date:   Mon Jun 10 17:03:37 2013 +0200
>>>
>>>     mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE
>>>
>>> Changed this behaviour?
>>
>> I realized I changed the behaviour to not cover for sdio func drivers,
>> that actually implements the pm callbacks - but do return -ENOSYS in
>> them. That wasn't obvious when looking at the code back then, sorry!
>
> Never mind, this behaviour change doesn't cause my problems but knowing
> whether this behaviour should be kept affects how I'm going to solve my
> problem.

So let's aim for the a proper solution instead of a quick hack.

Although apparently mwifiex, libertas and btmrvl_sdio (bluetooth) may
return -ENOSYS from the respective system supend callbacks, thus
expecting the card to be removed. Currently this won't happen, but
instead the suspend will be aborted, which is really bad.

I believe those driver's suspend callback should be fixed to not
return -ENOSYS. Returning 0 will, when MMC_PM_KEEP_POWER is not set,
power off the card similar what's done when removing the card - that
should be perfectly fine. Do note that the sdio func driver then
should expect the resume callback to invoked, instead of being
_probed_ at the next system resume.

>
> My problem is that, after the following commit:
>
> commit eed222aca8d077af3600b651176f6fd04d95cce1
> Author: Aaron Lu <aaron.lu@intel.com>
> Date:   Tue Mar 5 11:24:52 2013 +0800
>
>     mmc: sdio: bind acpi with sdio function device
>
> The SDIO function that has an ACPI node associated with will have the
> pm_domain assigned, which breaks the intention that during SDIO function
> device suspend phase nothing should be done by having a dummy BUS layer
> callback. The existence of the pm_domain for the SDIO function device
> will make its function driver's suspend callback gets called now. The
> end result is the function driver's suspend callback is called twice.

Why is the sdio bus ignored?

Are you saying the power domain is using the pm_generic_suspend for or
from it's ->suspend callback? If so, that could be the problem!?

>
> To solve this problem, I was wondering why SDIO function device has this
> 'special' requirement that nothing should be done at its own device
> suspend phase but instead, relies on its suspend callback gets called in
> its parent device's suspend callback. And then I realized the reason is
> for the special handling of -ENOSYS.

That's to my understanding not the only reason.

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.

You could debate whether that actually should be done though the PM
callbacks, or by some other SDIO specific callbacks. Haven't thought
it through completely yet.

>
> So if we could get rid of the -ENOSYS, my problem could be easily solved
> by deleting some lines in current code(the calling of function driver's
> suspend callback in mmc_sdio_suspend and the dummy system suspend/resume
> callback for SDIO bus). Buf if the behaviour has to be kept, I'll
> probably need to remove the pm_domain for the device and do some
> additional ACPI handing in mmc_sdio_suspend/resume for the function
> device.
>

So we have two different issues to address here.

Removing the option for sdio func drivers to return -ENOSYS from their
suspend callback - has already be done, though by my mistake. Anyway,
this won't solve your problem.

Additionally, I don't like putting this option back, since it's not
possible to remove the card in that path. Still we could handle
-ENOSYS and OK error and decide to power off the card. On the other
hand, we could instead fix the sdio func drivers, that should be quite
easy I think.

>>
>> There are no solution to this problem in the mmc core right now, since
>> we can't remove the card while we have reach the state when the
>> suspend callback is being invoked.
>>
>> Instead, the sdio func driver shall not implement the PM callbacks at
>> all. That behaviour means the mmc core will remove the card, but now
>> it's done a in an earlier phase of the system suspend when we are
>> still able to remove it.
>
> The libertas suspend callback is doing different things depending on
> different conditions - sometime it will enable wakeup capability and
> sometime it will want the mmc core to remove the device entirely by
> retuning -ENOSYS, so it may not be that easy by just deleting the
> callback, but I don't know for sure.

I had a look, the callback must remains.

As, stated - fix the suspend callback to not return -ENOSYS.

Kind regards
Uffe


>
> Thanks,
> Aaron

Re: SDIO driver return -ENOSYS behaviour change?

[Aaron Lu]

On 02/27/2014 09:05 PM, Ulf Hansson wrote:
> On 27 February 2014 12:26, Aaron Lu <aaron.lu@intel.com> wrote:
>> On 02/27/2014 06:18 PM, Ulf Hansson wrote:
>>> On 27 February 2014 10:10, Aaron Lu <aaron.lu@intel.com> wrote:
>>>> Hi Ulf,
>>>>
>>>> I was tracking some SDIO suspend problem and came across this. As Neil
>>>> mentioned here:
>>>> http://lkml.org/lkml/2012/3/25/20
>>>> Quote:
>>>> "
>>>> SDIO (and possible MMC in general) has a protocol where the suspend
>>>>  method can return -ENOSYS and this means "There is no point in suspending,
>>>>  just turn me off".
>>>> "
>>>>
>>>> It seems that the following commit:
>>>>
>>>> commit 810caddba42a54fe5db4e2664757a9a334ba359c
>>>> Author: Ulf Hansson <ulf.hansson@linaro.org>
>>>> Date:   Mon Jun 10 17:03:37 2013 +0200
>>>>
>>>>     mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE
>>>>
>>>> Changed this behaviour?
>>>
>>> I realized I changed the behaviour to not cover for sdio func drivers,
>>> that actually implements the pm callbacks - but do return -ENOSYS in
>>> them. That wasn't obvious when looking at the code back then, sorry!
>>
>> Never mind, this behaviour change doesn't cause my problems but knowing
>> whether this behaviour should be kept affects how I'm going to solve my
>> problem.
> 
> So let's aim for the a proper solution instead of a quick hack.

OK.

> 
> Although apparently mwifiex, libertas and btmrvl_sdio (bluetooth) may
> return -ENOSYS from the respective system supend callbacks, thus
> expecting the card to be removed. Currently this won't happen, but
> instead the suspend will be aborted, which is really bad.
> 
> I believe those driver's suspend callback should be fixed to not
> return -ENOSYS. Returning 0 will, when MMC_PM_KEEP_POWER is not set,
> power off the card similar what's done when removing the card - that
> should be perfectly fine. Do note that the sdio func driver then
> should expect the resume callback to invoked, instead of being
> _probed_ at the next system resume.

Good to know this.

> 
>>
>> My problem is that, after the following commit:
>>
>> commit eed222aca8d077af3600b651176f6fd04d95cce1
>> Author: Aaron Lu <aaron.lu@intel.com>
>> Date:   Tue Mar 5 11:24:52 2013 +0800
>>
>>     mmc: sdio: bind acpi with sdio function device
>>
>> The SDIO function that has an ACPI node associated with will have the
>> pm_domain assigned, which breaks the intention that during SDIO function
>> device suspend phase nothing should be done by having a dummy BUS layer
>> callback. The existence of the pm_domain for the SDIO function device
>> will make its function driver's suspend callback gets called now. The
>> end result is the function driver's suspend callback is called twice.
> 
> Why is the sdio bus ignored?

In __device_suspend, if pm_domain is set, the suspend callback is
fetched there, no matter if there is a suspend callback defined in the
pm_domain or not. In ACPI PM domain's case, the suspend callback is
NULL, so the driver's suspend callback is used then.

I consulted Rafael whether adding a NULL check before goto Run is OK
like the following shows:

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 1b41fca3d65a..506583d84ed4 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1160,7 +1160,8 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	if (dev->pm_domain) {
 		info = "power domain ";
 		callback = pm_op(&dev->pm_domain->ops, state);
-		goto Run;
+		if (callback)
+			goto Run;
 	}
 
 	if (dev->type && dev->type->pm) {

And Rafael said that would introduce regressions elsewhere, so it's a no
go.

> 
> Are you saying the power domain is using the pm_generic_suspend for or
> from it's ->suspend callback? If so, that could be the problem!?
> 
>>
>> To solve this problem, I was wondering why SDIO function device has this
>> 'special' requirement that nothing should be done at its own device
>> suspend phase but instead, relies on its suspend callback gets called in
>> its parent device's suspend callback. And then I realized the reason is
>> for the special handling of -ENOSYS.
> 
> That's to my understanding not the only reason.
> 
> 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.

>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?

> 
> You could debate whether that actually should be done though the PM
> callbacks, or by some other SDIO specific callbacks. Haven't thought
> it through completely yet.
> 
>>
>> So if we could get rid of the -ENOSYS, my problem could be easily solved
>> by deleting some lines in current code(the calling of function driver's
>> suspend callback in mmc_sdio_suspend and the dummy system suspend/resume
>> callback for SDIO bus). Buf if the behaviour has to be kept, I'll
>> probably need to remove the pm_domain for the device and do some
>> additional ACPI handing in mmc_sdio_suspend/resume for the function
>> device.
>>
> 
> So we have two different issues to address here.
> 
> Removing the option for sdio func drivers to return -ENOSYS from their
> suspend callback - has already be done, though by my mistake. Anyway,
> this won't solve your problem.
> 
> Additionally, I don't like putting this option back, since it's not
> possible to remove the card in that path. Still we could handle
> -ENOSYS and OK error and decide to power off the card. On the other
> hand, we could instead fix the sdio func drivers, that should be quite
> easy I think.
> 
>>>
>>> There are no solution to this problem in the mmc core right now, since
>>> we can't remove the card while we have reach the state when the
>>> suspend callback is being invoked.
>>>
>>> Instead, the sdio func driver shall not implement the PM callbacks at
>>> all. That behaviour means the mmc core will remove the card, but now
>>> it's done a in an earlier phase of the system suspend when we are
>>> still able to remove it.
>>
>> The libertas suspend callback is doing different things depending on
>> different conditions - sometime it will enable wakeup capability and
>> sometime it will want the mmc core to remove the device entirely by
>> retuning -ENOSYS, so it may not be that easy by just deleting the
>> callback, but I don't know for sure.
> 
> I had a look, the callback must remains.
> 
> As, stated - fix the suspend callback to not return -ENOSYS.

OK, I see, I'll try to come up with a patch for this, thanks for the
suggestion!

-Aaron

> 
> Kind regards
> Uffe
> 
> 
>>
>> Thanks,
>> Aaron

Re: SDIO driver return -ENOSYS behaviour change?

[Ulf Hansson]

On 28 February 2014 03:37, Aaron Lu <aaron.lu@intel.com> wrote:
> On 02/27/2014 09:05 PM, Ulf Hansson wrote:
>> On 27 February 2014 12:26, Aaron Lu <aaron.lu@intel.com> wrote:
>>> On 02/27/2014 06:18 PM, Ulf Hansson wrote:
>>>> On 27 February 2014 10:10, Aaron Lu <aaron.lu@intel.com> wrote:
>>>>> Hi Ulf,
>>>>>
>>>>> I was tracking some SDIO suspend problem and came across this. As Neil
>>>>> mentioned here:
>>>>> http://lkml.org/lkml/2012/3/25/20
>>>>> Quote:
>>>>> "
>>>>> SDIO (and possible MMC in general) has a protocol where the suspend
>>>>>  method can return -ENOSYS and this means "There is no point in suspending,
>>>>>  just turn me off".
>>>>> "
>>>>>
>>>>> It seems that the following commit:
>>>>>
>>>>> commit 810caddba42a54fe5db4e2664757a9a334ba359c
>>>>> Author: Ulf Hansson <ulf.hansson@linaro.org>
>>>>> Date:   Mon Jun 10 17:03:37 2013 +0200
>>>>>
>>>>>     mmc: core: Validate suspend prerequisites for SDIO at SUSPEND_PREPARE
>>>>>
>>>>> Changed this behaviour?
>>>>
>>>> I realized I changed the behaviour to not cover for sdio func drivers,
>>>> that actually implements the pm callbacks - but do return -ENOSYS in
>>>> them. That wasn't obvious when looking at the code back then, sorry!
>>>
>>> Never mind, this behaviour change doesn't cause my problems but knowing
>>> whether this behaviour should be kept affects how I'm going to solve my
>>> problem.
>>
>> So let's aim for the a proper solution instead of a quick hack.
>
> OK.
>
>>
>> Although apparently mwifiex, libertas and btmrvl_sdio (bluetooth) may
>> return -ENOSYS from the respective system supend callbacks, thus
>> expecting the card to be removed. Currently this won't happen, but
>> instead the suspend will be aborted, which is really bad.
>>
>> I believe those driver's suspend callback should be fixed to not
>> return -ENOSYS. Returning 0 will, when MMC_PM_KEEP_POWER is not set,
>> power off the card similar what's done when removing the card - that
>> should be perfectly fine. Do note that the sdio func driver then
>> should expect the resume callback to invoked, instead of being
>> _probed_ at the next system resume.
>
> Good to know this.
>
>>
>>>
>>> My problem is that, after the following commit:
>>>
>>> commit eed222aca8d077af3600b651176f6fd04d95cce1
>>> Author: Aaron Lu <aaron.lu@intel.com>
>>> Date:   Tue Mar 5 11:24:52 2013 +0800
>>>
>>>     mmc: sdio: bind acpi with sdio function device
>>>
>>> The SDIO function that has an ACPI node associated with will have the
>>> pm_domain assigned, which breaks the intention that during SDIO function
>>> device suspend phase nothing should be done by having a dummy BUS layer
>>> callback. The existence of the pm_domain for the SDIO function device
>>> will make its function driver's suspend callback gets called now. The
>>> end result is the function driver's suspend callback is called twice.
>>
>> Why is the sdio bus ignored?
>
> In __device_suspend, if pm_domain is set, the suspend callback is
> fetched there, no matter if there is a suspend callback defined in the
> pm_domain or not. In ACPI PM domain's case, the suspend callback is
> NULL, so the driver's suspend callback is used then.

Will it be possible to add a suspend callback in the ACPI PM domain,
which then respects susbystems callbacks before it uses
pm_generic_suspend?

>
> I consulted Rafael whether adding a NULL check before goto Run is OK
> like the following shows:
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 1b41fca3d65a..506583d84ed4 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1160,7 +1160,8 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>         if (dev->pm_domain) {
>                 info = "power domain ";
>                 callback = pm_op(&dev->pm_domain->ops, state);
> -               goto Run;
> +               if (callback)
> +                       goto Run;
>         }
>
>         if (dev->type && dev->type->pm) {
>
> And Rafael said that would introduce regressions elsewhere, so it's a no
> go.
>
>>
>> Are you saying the power domain is using the pm_generic_suspend for or
>> from it's ->suspend callback? If so, that could be the problem!?
>>
>>>
>>> To solve this problem, I was wondering why SDIO function device has this
>>> 'special' requirement that nothing should be done at its own device
>>> suspend phase but instead, relies on its suspend callback gets called in
>>> its parent device's suspend callback. And then I realized the reason is
>>> for the special handling of -ENOSYS.
>>
>> That's to my understanding not the only reason.
>>
>> 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".

>
> 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.)

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.

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

Kind regards
Ulf Hansson

>
>>
>> You could debate whether that actually should be done though the PM
>> callbacks, or by some other SDIO specific callbacks. Haven't thought
>> it through completely yet.
>>
>>>
>>> So if we could get rid of the -ENOSYS, my problem could be easily solved
>>> by deleting some lines in current code(the calling of function driver's
>>> suspend callback in mmc_sdio_suspend and the dummy system suspend/resume
>>> callback for SDIO bus). Buf if the behaviour has to be kept, I'll
>>> probably need to remove the pm_domain for the device and do some
>>> additional ACPI handing in mmc_sdio_suspend/resume for the function
>>> device.
>>>
>>
>> So we have two different issues to address here.
>>
>> Removing the option for sdio func drivers to return -ENOSYS from their
>> suspend callback - has already be done, though by my mistake. Anyway,
>> this won't solve your problem.
>>
>> Additionally, I don't like putting this option back, since it's not
>> possible to remove the card in that path. Still we could handle
>> -ENOSYS and OK error and decide to power off the card. On the other
>> hand, we could instead fix the sdio func drivers, that should be quite
>> easy I think.
>>
>>>>
>>>> There are no solution to this problem in the mmc core right now, since
>>>> we can't remove the card while we have reach the state when the
>>>> suspend callback is being invoked.
>>>>
>>>> Instead, the sdio func driver shall not implement the PM callbacks at
>>>> all. That behaviour means the mmc core will remove the card, but now
>>>> it's done a in an earlier phase of the system suspend when we are
>>>> still able to remove it.
>>>
>>> The libertas suspend callback is doing different things depending on
>>> different conditions - sometime it will enable wakeup capability and
>>> sometime it will want the mmc core to remove the device entirely by
>>> retuning -ENOSYS, so it may not be that easy by just deleting the
>>> callback, but I don't know for sure.
>>
>> I had a look, the callback must remains.
>>
>> As, stated - fix the suspend callback to not return -ENOSYS.
>
> OK, I see, I'll try to come up with a patch for this, thanks for the
> suggestion!
>
> -Aaron
>
>>
>> Kind regards
>> Uffe
>>
>>
>>>
>>> Thanks,
>>> Aaron
>

Re: SDIO driver return -ENOSYS behaviour change?

[Aaron Lu]

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