On Tue, Apr 23, 2013 at 11:42 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 23 Apr 2013, Vivek Gautam wrote: > >> Hi, >> >> >> On Tue, Apr 23, 2013 at 10:23 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Tue, 23 Apr 2013, Vivek Gautam wrote: >> > >> >> >> Alright, so here's my understanding: >> >> >> >> >> >> I suggested letting e.g. DWC3 enable the PHY's runtime_pm; Alan said >> >> >> that it could be done before that so that DWC3 sees an enabled PHY >> >> >> during probe. >> >> > >> >> > Basically right. Help me to understand the overall situation a little >> >> > better: >> >> > >> >> > What code registers the PHY initially? >> >> PHY is added to global list by PHY drivers (like >> >> phy-samsung-usb2.c/phy-omap-usb2.c) >> >> by usb_add_phy() API >> > >> > Then this routine should initialize the PHY. The initialized state >> > could be either active or suspended, your choice. Suspended would be >> > best, in case the PHY never gets used. >> >> Fair enough. >> >> > >> >> > What routine does the DWC3 driver call to register itself >> >> > as a consumer of the PHY? >> >> I think DWC3 doesn't registers itself as consumer of PHY, >> >> rather it gets that PHY from >> >> the list using devm_usb_get_phy()/devm_usb_get_phy_by_phandle() API. >> >> DWC3 can now call PHY's initialization sequence using usb_phy_init(). >> >> So, before DWC3 initializes the PHY, PHYs should be in active state. >> > >> > Then usb_phy_init should make sure the PHY is in the active state. If >> > usb_add_phy() left the PHY suspended, then this routine should call >> > pm_runtime_get_sync(). >> >> Right >> >> > >> > After DWC3 (or any other driver) has acquired the PHY, it can call >> > pm_runtime_put/get() however it likes, so long as the calls balance >> > properly. If the driver isn't runtime-PM aware then it won't use any >> > of these calls, and the PHY will remain active the entire time. >> >> Alright, so DWC3 (or any other consumer of PHY) should do minimal to >> handle runtime state of PHYs; get() when accessing PHY and put() when it's done >> with it. > > Yes. The first operation will generally be a put, because > usb_phy_init() will leave the PHY in an active state. Alright. > >> >> > Likewise, what routine does it call to unregister itself? >> >> Once DWC3's remove() is called PHYs are put. >> > >> > Is there a routine analogous to usb_phy_init() that gets called when >> > PHY is released? That routine would do the opposite of usb_phy_init(), >> > putting the PHY back into its initialized state. >> >> Yes, ofcourse there's a routine usb_phy_shutdown(). So this will be >> calling put_sync() >> to put PHYs back to its initialized state. Right ? > > Correct. Hmm. Thanks for explaining things here and keeping patience to my queries :-) Felipe, thanks to you too for the discussion :-) I shall update the patchset asap. -- Best Regards Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
