On Wed, 2 Oct 2013, yoma sophian wrote: > hi alan: > > 2013/10/2 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > > On Wed, 2 Oct 2013, yoma sophian wrote: > > > >> 1. in susped, we will gate our ehci clk > >> in resumt, we need to release clk gating to let ehci control work. > >> and above are platform specific behavior need to do > >> there seems no such place to do above 2 things. > > > > You don't do these things in the USB suspend routine; you do them in > > the controller suspend routine. For example, take a look at > > s5p_ehci_suspend() and s5p_ehci_resume() in ehci-s5p.c. > I found what you mentioned. > 1. When will platform register dev_pm_ops be called? Is it called > before or after usb_device_pm_ops ? The platform suspend routine is called after the USB suspend routine. The platform resume routine is called before the USB resume routine. > 2. in ehci-s5p.c, it create a ".of_match_table". > Under what circumstance, the match will happen? > That mean how could I make sure the .pm I register in > platform_driver will be matched and activated in the feature? The of_match_table entry is used during probe. It matters only for drivers that use Open Firmware (i.e., Device Tree). > >> 2. in ehci_bus_resume, which handle ehci go back from both suspend/hibernate. > >> This function handle ehci basic register default setting, such as > >> re-init operational registers and restore CMD_RUN, framelist size, and > >> irq threshold > > Why don't we put "handle basic register default setting, such as > re-init operational registers and restore CMD_RUN, framelist size, and > irq threshold" as pci_suspend and pci_resume like xhci does? Some of those things could indeed be moved from ehci_bus_resume to ehci_resume. Not CMD_RUN, though. However, xHCI is fundamentally different from EHCI. A single xHCI controller manages two physically independent buses: a SuperSpeed bus and a full/low/high-speed bus. An EHCI controller, on the other hand, manages only one bus. Therefore the drivers need to be somewhat different. > That mean ehci_bus_resume will handle both "usb port resume" and > "system hibernate" jobs. But xhci_bus_resume only handle "usb port > resume", right? No. ehci_bus_resume and xhci_bus_resume both handle bus resume jobs, whereas ehci_resume and xhci_resume both handle controller resume jobs. Bus suspend means putting an entire USB bus into low-power mode. In particular, it means the controller should stop sending packets (even SOF packets). Controller suspend means putting the controller itself into low-power mode. System sleep (which includes system suspend and system hibernate) involves both sorts of job: bus suspend/resume _and_ controller suspend/resume. 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
