On Monday, November 26, 2012 09:05:58 AM Aaron Lu wrote: > On 11/26/2012 09:03 AM, Rafael J. Wysocki wrote: > > On Monday, November 26, 2012 08:48:51 AM Aaron Lu wrote: > >> On 11/26/2012 08:50 AM, Rafael J. Wysocki wrote: > >>> On Tuesday, November 20, 2012 04:59:57 PM Aaron Lu wrote: > >>>> On 11/20/2012 02:00 PM, Aaron Lu wrote: > >>>>> On 11/19/2012 10:56 PM, Tejun Heo wrote: > >>>>>> I really think we need a way for (auto)pm and event polling to talk to > >>>>>> each other so that autopm can tell event poll to sod off while pm is > >>>>>> in effect. Trying to solve this from inside libata doesn't seem > >>>>>> right. The problem, again, seems to be figuring out which hardware > >>>>>> device maps to which block device. Hmmm... Any good ideas? > >>>>> > >>>>> A possible way of doing this is using pm qos. > >>>>> > >>>>> We currently have 2 pm qos flags, NO_POWER_OFF and REMOTE_WAKEUP, and we > >>>>> can add another one: NO_POLL, use it like the following: > >>>>> 1 Set the NO_POLL pm qos flag when the underlying driver thinks it is no > >>>>> longer necessary. In the ZPODD's case, it should be set when the > >>>>> device is to be powered off; > >>>>> 2 Clear it when poll is necessary again. In the ZPODD's case, when power > >>>>> is re-gained, this flag will be cleared. > >>>> > >>>> > >>>>> 3 In the disk_events_workfn, check if this flag is set, if so, simply > >>>>> return. > >>>> > >>>> It should be, skip calling disk->fops->check_events, but still queue the > >>>> work for next time's poll. > >>>> > >>>> -Aaron > >>>> > >>>>> > >>>>> The disk->driverfs_dev can be used to host the pm qos flag, ATA layer > >>>>> can access it through ata_device->sdev->sdev_gendev. > >>>>> > >>>>> Is this OK? > >>> > >>> No, I don't think so. PM QoS is about telling the layer that will put the > >>> device into low-power states what states are to be taken into consideration. > >>> In this case, however, we need to tell someone else that the device has been > >>> turned off. Clearly, we need a way to do that, but not through PM QoS. > >>> > >>> Did you consider using pm_runtime_suspended() to check the device status? > >> > >> The problem is, a device can be in runtime suspended state while still > >> needs to be polled... > > > > Well, maybe this is the problem, then? Why does it need to be polled when > > suspended? > > For ODDs, poll is not necessary only when ZP capable ODD is powered off. > For other ODDs, poll still needs to go on. > > ZP capable ODDs: > - runtime suspended, power remained(due to NO_POWER_OFF qos flag) > poll is needed > -- runtime suspended, power removed > poll is not needed > > Non ZP capable ODDs: > -- runtime suspended, power remained (power will never be removed) > poll is needed > > If we do not poll for the powered on case, we will lose media change > event. But the media change event should change the status from suspended to active, shouldn't it? Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
