On 28 February 2014 03:37, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > On 02/27/2014 09:05 PM, Ulf Hansson wrote: >> On 27 February 2014 12:26, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: >>> On 02/27/2014 06:18 PM, Ulf Hansson wrote: >>>> On 27 February 2014 10:10, Aaron Lu <aaron.lu@xxxxxxxxx> 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@xxxxxxxxxx> >>>>> 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@xxxxxxxxx> >>> 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
