On Wed, Sep 26, 2012 at 7:18 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > On Wednesday, September 26, 2012, Aaron Lu wrote: >> On Tue, Sep 25, 2012 at 11:45:34PM +0200, Rafael J. Wysocki wrote: >> > On Tuesday, September 25, 2012, Aaron Lu wrote: >> > > On 09/25/2012 10:23 PM, Oliver Neukum wrote: >> > > > On Tuesday 25 September 2012 22:20:21 Aaron Lu wrote: >> > > >> On Tue, Sep 25, 2012 at 01:47:52PM +0200, Rafael J. Wysocki wrote: >> > > >>> On Tuesday, September 25, 2012, Aaron Lu wrote: >> > > >>>> I'm thinking of enabling this GPE in sr_suspend once we decided that it >> > > >>>> is ready to be powered off, so the time frame between sr_suspend and >> > > >>>> when the power is actually removed in libata should be taken care of by >> > > >>>> the GPE. If GPE fires, the notification function will request a runtime >> > > >>>> resume of the device. Does this sound OK? >> > > >>> >> > > >>> Well, depending on the implementation. sr_suspend() should be rather >> > > >>> generic, but the ACPI association (including the GPE thing) is specific to ATA. >> > > >> >> > > >> Sorry, but don't quite understand this. >> > > >> >> > > >> We have ACPI bindings for scsi devices, isn't that for us to use ACPI >> > > >> when needed in scsi? >> > > > >> > > > We don't have ACPI bindings for generic SCSI devices. We have such >> > > > bindings for SATA drives. You can put such things only in sr if it applies >> > > > to all (maybe most) types of drives. >> > > >> > > OK. Then these scsi bindings for sata drives will be pretty much of >> > > no use I think. >> > > >> > > > >> > > >> BTW, if sr_suspend should be generic, that would suggest I shouldn't >> > > >> write any ZPODD related code there, right? Any suggestion where these >> > > >> code should go then? >> > > > >> > > > libata. Maybe some generic hooks can be called in sr_suspend(). >> > > >> > > Thanks for the suggestion. >> > > The problem is, I need to know whether the door is closed and if there >> > > is a medium inside. I've no way of getting such information in libata. >> > >> > How does sr get to know it in the libata case? >> >> By executing a test_unit_ready command. >> >> Libata does/should not have any routine to do this, it is one of the >> transport of SCSI devices and it relies on SCSI driver to manage the >> device(both disk and ODD). >> >> > >> > > > PS: Are you sure sr_suspend() handles DVD-RAMs correctly? >> > > >> > > No. Is there a spec for it? >> > > Considering there are many different drives sr handle, is it possible to >> > > write a generic sr_suspend? >> > > Maybe your suggestion of callback is the way to go. >> > > What about this idea, if we find this is a ZPODD capable drive, we >> > > enable runtime suspend for it and write a suspend callback according to >> > > ZPODD spec. For other drives that does not have a suspend callback, we >> > > do not enable runtime suspend. >> > >> > You can enable runtime PM for all kinds of drives, but make the suspend >> > and resume callbacks only do something for ZPODD ones. This may allow their >> > parents to use runtime PM (as Alan said earlier in this thread), even if the >> > drives themseleves are not really physically suspended. >> >> Sounds good. >> >> > >> > > Does this sound reasonable? >> > >> > First, we need to know when the drive is not in use. That information >> > we can get from the sr's runtime PM and it looks like we need to notify >> > libata about that somehow. I'm not sure what mechanism is the best for >> > that at the moment. >> >> The current mechanism to notify libata is by rumtime suspend. When scsi >> device is runtime suspended, its parent device will be suspended. And >> ata_port is one of the ancestor devices of scsi device, and we will >> remove its power in ata_port's runtime suspend callback. > > The problem, then, is that the ata_port's runtime suspend callback would > have to know whether or not power can be removed from the drive. > > I'm going to post patches introducing a "no power off" flag for PM QoS, > among other things, today or tomorrow. I suppose this flag might be used to > tell the ata_port's suspend not to remove power from the attached device. Cool, thanks. > >> > Second, when the device is resumed by remote wakeup, we need to notify >> > sr about that. A "resume" alone is not sufficient, though, because it may >> > be necessary to open the tray. Perhaps in that case we can use the same >> > mechanism by which user events are processed by libata and delivered to sr? >> >> Thanks for the suggestion. >> I'm not aware of any user events processed by libata. Do you mean the >> events_checking poll? > > Yes, basically. In the remote wakeup case libata might report the same > status as in the "user pressed the eject button" situation happening > normally with power on. Maybe I didn't explain it clearly. The "user pressed the eject button" is reported by ACPI through GPE, while the events_checking poll sends a command to the device to let it report events like media_change, etc. And the events is reported to user space, that doesn't seem can help us in this case. Thanks, Aaron -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
