On 11/26/2012 09:11 AM, Rafael J. Wysocki wrote: > 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? We need a way PM code can tell block layer that it is not necessary to poll the device now, and runtime suspended is not enough, so we need another way. Thanks, Aaron > > Rafael > > -- 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
