Messages in this thread | | | From | Mathias Nyman <> | Subject | Re: [PATCH v2] xhci: fix runtime PM imbalance in USB2 resume | Date | Mon, 28 Feb 2022 12:56:39 +0200 |
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On 25.2.2022 9.15, Henry Lin wrote: > USB2 resume starts with usb_hcd_start_port_resume() in port status > change handling for RESUME link state. usb_hcd_end_port_resume() call is > needed to keep runtime PM balance.
For normal usb2 port resume the usb_hcd_end_port_resume() is called when resume has been signaled for long enough in xhci_handle_usb2_port_link_resume().
This is also where driver directs the port to go from Resume state to U0. Port can't do this without driver directing it.
If there's a failure during resume signaling (disconnect, reset, error) then stale resume variables are detected in xhci_get_port_status() and usb_hcd_end_port_resume() is called.
I do now see a231ec41e6f6 ("xhci: refactor U0 link state handling in get_port_status") does change order of checking and clearing stale resume variables, but this should only happen if the first port state we read is a fully enabled functional U0 state after a failed resume.
Could you expand a bit how this was detected?
> > Fixes: a231ec41e6f6 ("xhci: refactor U0 link state handling in get_port_status") > Signed-off-by: Henry Lin <henryl@nvidia.com> > --- > drivers/usb/host/xhci-hub.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c > index df3522dab31b..4a8b07b8ee01 100644 > --- a/drivers/usb/host/xhci-hub.c > +++ b/drivers/usb/host/xhci-hub.c > @@ -1090,6 +1090,8 @@ static void xhci_get_usb2_port_status(struct xhci_port *port, u32 *status, > if (link_state == XDEV_U0) { > bus_state->resume_done[portnum] = 0; > clear_bit(portnum, &bus_state->resuming_ports); > + usb_hcd_end_port_resume(&port->rhub->hcd->self, > + portnum);
This will call usb_hcd_end_port_resume() every time port is in normal enabled U0 state even if resume was never signaled, or port suspended.
-Mathias
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