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. > >> > 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. Alan Stern -- 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
