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From:   Henry Lin <henryl@nvidia.com>
To:     Mathias Nyman <mathias.nyman@linux.intel.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     Mathias Nyman <mathias.nyman@intel.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] xhci: fix runtime PM imbalance in USB2 resume
Thread-Topic: [PATCH v2] xhci: fix runtime PM imbalance in USB2 resume
Thread-Index: AQHYKhd7AopZ8pn1EUiip/DzNcJli6yoz4qAgAF/L3WAAGTvgIAAOaxB
Date:   Tue, 1 Mar 2022 19:18:38 +0000
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References: <20220225055311.92447-1-henryl@nvidia.com>
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> Maybe only call usb_hcd_end_port_resume() if xhci_irq() detected the devi=
ce-initiated=0A=
> resume. i.e. set a value to resume_done[portnum] and called usb_hcd_start=
_port_resume()=0A=
> something like:=0A=
>=0A=
> @@ -1088,6 +1088,8 @@ static void xhci_get_usb2_port_status(struct xhci_p=
ort *port, u32 *status,=0A=
>                 if (link_state =3D=3D XDEV_U2)=0A=
>                         *status |=3D USB_PORT_STAT_L1;=0A=
>                 if (link_state =3D=3D XDEV_U0) {=0A=
> +                       if (bus_state->resume_done[portnum])=0A=
> +                               usb_hcd_end_port_resume(&port->rhub->hcd-=
>self, portnum);=0A=
>                         bus_state->resume_done[portnum] =3D 0;=0A=
>                         clear_bit(portnum, &bus_state->resuming_ports);=
=0A=
This looks good. I can submit a new version based on this.=0A=
=0A=
> Also xhci_bus_resume() only resumes ports that were forcefully suspended =
to U3 in xhci_bus_suspend().=0A=
> Could be worth checking why that device wasn't already in U3 when suspend=
 reached xhci_bus_suspend().=0A=
It happens when we trigger USB device-initiated resume to bring system out =
of system suspend state.=0A=
For example, we can connect an USB2 external hub on root port and put syste=
m into suspend state. The USB2=0A=
external hub (the port it connects to) is in U3 after xhci_bus_suspend(). O=
nce we connect a USB device=0A=
to downstream port of the USB2 external hub, the hub will trigger device in=
itiated resume to wake up the=0A=
system. During system resume, XHCI controller will report the USB2 external=
 hub is in RESUME state.=0A=
=0A=
Thanks,=0A=
Henry=0A=