On Thu, 3 Jul 2014, Lu, Baolu wrote:
> Hi,
>
> I am using an ASUS T100TA with dock attached. I installed Ubuntu Linux
> on eMMC and customized the kernel.
>
> I started from "echo mem > /sys/power/state". Kernel starts its
> processes to put the system into suspend mode. Before kernel executes to
> xhci_bus_suspend(), xHC USB 2 root hub port (where keyboard on dock
> connected) reports a port resume event. In response of this event, xHCI
> roothub driver sets the corresponding bit in bus_state->resuming_ports
> and intent to clear it when hcd->rh_timer expires 20ms later.
>
> handle_port_status():
>
> xhci_dbg(xhci, "resume HS port %d\n", port_id);
> bus_state->resume_done[faked_port_index] =
> jiffies +
> msecs_to_jiffies(20);
> set_bit(faked_port_index,
> &bus_state->resuming_ports);
> mod_timer(&hcd->rh_timer,
> bus_state->resume_done[faked_port_index]);
>
> When system executes to xhci_bus_suspend(), it checks
> bus_state->resuming_ports. It stops here since bus_state->resuming_ports
> has been set.
>
> xhci_bus_suspend():
>
> if (hcd->self.root_hub->do_remote_wakeup) {
> if (bus_state->resuming_ports) {
> spin_unlock_irqrestore(&xhci->lock, flags);
> xhci_dbg(xhci, "%s: suspend failed because "
> "a port is resuming\n",
> __func__);
> return -EBUSY;
> }
> }
>
> This failure can always be reproduced when I use the keyboard on T100TA
> dock. But it doesn't show up with an external USB keyboard. Does anybody
> have any hints for me?
It's possible that commit d6236f6d1d88 in the usb-linus branch of Greg
KH's USB git tree may be relevant here. It's a long shot, though.
Basically, it sounds like a bug in the dock hardware.
Alan Stern
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