On Fri, 14 Jun 2013, Roger Quadros wrote: > >> hi > >> The following is my understanding. > >> I think for PHY initialization and shutdown part, it is generic for > >> other parts. > >> PHY initialization need to be called before hc_driver->reset is called. > >> I think it can be added at usb_add_hcd. > >> For PHY shutdown, it can be added at usb_remove_hcd. > > > > Yes, that should work. > > I don't think this will work with OMAP USB host controller when used in > Transceiver-less mode (e.g. HSIC). In this mode we need to release the HSIC > reset (mapped to PHY init), after the EHCI controller is up and running. > > On the other hand, in the PHY mode, the PHY needs to be initialized (brought out > of reset) before the EHCI controller starts. In other words, transceiver-less mode effectively works without using a software-controlled PHY? > This behavior might be different on other controllers. Generalization is good > as long as there is an override available for the controllers to handle the > PHY init/shutdown themselves. To avoid PHY init/shutdown, the platform driver should simply leave the generic PHY pointer (which has not yet been added to struct hcd) set to NULL. > >> For suspend/resume, i do not know how to add it. For our EHCI driver, > >> when system goes to deep idle states, we just directly shutdown the > >> hcd and initialize it again when the system goes back. > > > > You shut down the host controller? Then how does it detect wakeup > > events? And how does it know if a device was disconnected while the > > power was off? > > > > On OMAP as well we are aiming to cut clocks to the host controller (state saved) > during bus/system suspend. PHY is in low power mode capable of detecting wakeup events. > The SoC is configured to wake up on any I/O activity on the PHY pins. Upon > detection of PHY related I/O event, SoC wakes up, we restore the host controller state > and proceed as normal. Maybe it's just me, but turning off USB Vbus power during suspend seems like a bad idea. Except for the case where all the root-hub ports are disabled (such as when no devices are plugged in) -- in that case it's fine. But turning off power to an enabled device should be avoided, even though the kernel does a decent job of recovering when this happens. Not all devices respond well to this sort of treatment. Alan Stern -- 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
