On Wed, Nov 19, 2014 at 1:47 AM, 李云志 <lyz@xxxxxxxxxxxxxx> wrote: > hi Julius & Alan > > Shall we use dwc2's private status "hsotg->lx_state" here instesd of > "hcd->state" for checking root hub is in suspend state ? > I see the EHCI driver do something like this(ehci->rh_state == > EHCI_RH_SUSPENDED) before resume the root hub. It's not this simple, because lx_state only relates to the status of the one port on the DWC2. That may be suspended even though the root hub is not. The USB core differentiates between suspending individual ports, and suspending the whole root hub (which should automatically suspend all ports in a host-controller-specific manner). This distinction may seem silly on DWC2 because there is only one port to suspend, but you still need to make it so that the USB core doesn't get confused. So the different things you need to keep track of are: * is the one port individually suspended (through the hub_control(SetPortFeature(PORT_SUSPEND)) method) * is the root hub suspended (through calling bus_suspend()) * if the root hub gets suspended (through bus_suspend()), had the port already been suspended before that (through a earlier hub_control())... this is the thing I mentioned in your other patch You can decide whether you want to bake that all into one variable somehow or make it three, but we need to be able to tell all of these things apart. The third bullet point will also require you to prevent races of hub_control() with bus_suspend() (not sure if the kernel already guarantees that or not), so I think we may have to rethink the way the spinlock works (because it currently doesn't cover that). -- 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
