On Tue, Aug 23, 2016 at 04:02:48PM +0530, Vaibhav Hiremath wrote: > > > On Monday 15 August 2016 02:43 PM, Peter Chen wrote: > >Hi all, > > > >This is a follow-up for my last power sequence framework patch set [1]. > >According to Rob Herring and Ulf Hansson's comments[2], I use a generic > >power sequence library for parsing the power sequence elements on DT, > >and implement generic power sequence on library. The host driver > >can allocate power sequence instance, and calls pwrseq APIs accordingly. > > > >In future, if there are special power sequence requirements, the special > >power sequence library can be created. > > > >This patch set is tested on i.mx6 sabresx evk using a dts change, I use > >two hot-plug devices to simulate this use case, the related binding > >change is updated at patch [1/6], The udoo board changes were tested > >using my last power sequence patch set.[3] > > > >Except for hard-wired MMC and USB devices, I find the USB ULPI PHY also > >need to power on itself before it can be found by ULPI bus. > > > >[1] http://www.spinics.net/lists/linux-usb/msg142755.html > >[2] http://www.spinics.net/lists/linux-usb/msg143106.html > >[3] http://www.spinics.net/lists/linux-usb/msg142815.html > (Please ignore my response on V2) > > Sorry being so late in the discussion... > > If I am not missing anything, then I am afraid to say that the > generic library > implementation in this patch series is not going to solve many of > the custom > requirement of power on, off, etc... > I know you mentioned about adding another library when we come > across such platforms, but should we not keep provision (or easy > hooks/path) > to enable that ? > > Let me bring in the use case I am dealing with, > > > Host > | > V > USB port > ------------------------------------------------------------ > | > V > USB HUB device (May need custom on/off seq) > | > V > ============================= > | | > V V > Device-1 Device-2 > (Needs special power (Needs special power > on/off sequence. on/off sequence. > Also may need custom Also, may need custom > sequence for sequence for > suspend/resume) suspend/resume) > > > Note: Both Devices are connected to HUB via HSIC and may differ > in terms of functionality, features they support. > > In the above case, both Device-1 and Device-2, need separate > power on/off sequence. So generic library currently we have in this > patch series is not going to satisfy the need here. > > I looked at all 6 revisions of this patch-series, went through the > review comments, and looked at MMC power sequence code; > what I can say here is, we need something similar to > MMC power sequence here, where every device can have its own > power sequence (if needed). > > I know Rob is not in favor of creating platform device for > this, and I understand his comment. > If not platform device, but atleast we need mechanism to > connect each device back to its of_node and its respective > driver/library fns. For example, the Devices may support different > boot modes, and platform driver needs to make sure that > the right sequence is followed for booting. > > Peter, My apologies for taking you back again on this series. > I am OK, if you wish to address this in incremental addition, > but my point is, we know that the current generic way is not > enough for us, so I think we should try to fix it in initial phase only. > Rob, it seems generic power sequence can't cover all cases. Without information from DT, we can't know which power sequence for which device. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
