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SubjectRe: [PATCH v2] xhci: Set port link to RxDetect if port is not enabled after resume
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Hi Mathias,

> On Mar 11, 2020, at 12:04, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
>
> On Dell TB16, Realtek USB ethernet (r8152) connects to an SMSC hub which
> then connects to ASMedia xHCI's root hub:
>
> /: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
> |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/7p, 5000M
> |__ Port 2: Dev 3, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M
>
> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 004 Device 002: ID 0424:5537 Standard Microsystems Corp. USB5537B
> Bus 004 Device 003: ID 0bda:8153 Realtek Semiconductor Corp. RTL8153 Gigabit Ethernet Adapter
>
> The port is disabled after resume:
> xhci_hcd 0000:3f:00.0: Get port status 4-1 read: 0x280, return 0x280
>
> According to xHCI 4.19.1.2.1, we should set link to RxDetect to transit
> it from disabled state to disconnected state, which allows the port to
> be set to U0 and completes the resume process.
>
> My own test shows port can still resume when it's not enabled, as long
> as its link is in U states. So constrain the new logic only when link is
> not in any U state.
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

Do you think this is a proper fix?

Kai-Heng

> ---
> drivers/usb/host/xhci-hub.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index a9c87eb8951e..263f9a9237a1 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -1776,6 +1776,14 @@ int xhci_bus_resume(struct usb_hcd *hcd)
> clear_bit(port_index, &bus_state->bus_suspended);
> continue;
> }
> +
> + /* 4.19.1.2.1 */
> + if (!(portsc & PORT_PE) && (portsc & PORT_PLS_MASK) > XDEV_U3) {
> + portsc = xhci_port_state_to_neutral(portsc);
> + portsc &= ~PORT_PLS_MASK;
> + portsc |= PORT_LINK_STROBE | XDEV_RXDETECT;
> + }
> +
> /* resume if we suspended the link, and it is still suspended */
> if (test_bit(port_index, &bus_state->bus_suspended))
> switch (portsc & PORT_PLS_MASK) {
> --
> 2.17.1
>

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