Re: [PATCH v2 3/4] usb: xhci: Allow custom op for usb_link_tunnel_mode reporting

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Wed, Jul 15, 2026, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> 
> The Thunderbolt framework relies on the USB core to create device links
> for tunneled ports, so that the USB3 controller is only kept
> runtime-resumed for the duration of the tunneling.
> 
> Currently, retrieving that information is only possibe on Intel XHCI
> hosts, through a vendor-specific capability. Extend xhci-plat to allow
> plumbing a custom one.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
>  drivers/usb/host/xhci-hub.c  | 13 +++++++++----
>  drivers/usb/host/xhci-plat.c |  2 ++
>  drivers/usb/host/xhci-plat.h |  1 +
>  drivers/usb/host/xhci.c      |  3 ++-
>  drivers/usb/host/xhci.h      |  5 ++++-
>  5 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 402e98ab95ee..9964cbd154ab 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -749,7 +749,7 @@ static int xhci_exit_test_mode(struct xhci_hcd *xhci)
>  }
>  
>  /**
> - * xhci_port_is_tunneled() - Check if USB3 connection is tunneled over USB4
> + * xhci_port_tunnel_mode() - Check if USB3 connection is tunneled over USB4
>   * @xhci: xhci host controller
>   * @port: USB3 port to be checked.
>   *
> @@ -763,7 +763,7 @@ static int xhci_exit_test_mode(struct xhci_hcd *xhci)
>   * detecting USB3 over USB4 tunnels. USB_LINK_NATIVE or USB_LINK_TUNNELED
>   * otherwise.
>   */
> -enum usb_link_tunnel_mode xhci_port_is_tunneled(struct xhci_hcd *xhci,
> +enum usb_link_tunnel_mode xhci_port_tunnel_mode(struct xhci_hcd *xhci,
>  						struct xhci_port *port)
>  {
>  	void __iomem *base = &xhci->cap_regs->hc_capbase;
> @@ -787,8 +787,13 @@ enum usb_link_tunnel_mode xhci_port_is_tunneled(struct xhci_hcd *xhci,
>  	/* Fall back to the legacy Intel-specific ext_cap */
>  	hcd = xhci_to_hcd(xhci);
>  	if (!dev_is_pci(hcd->self.controller) ||
> -	    to_pci_dev(hcd->self.controller)->vendor != PCI_VENDOR_ID_INTEL)
> -		return USB_LINK_UNKNOWN;
> +	    to_pci_dev(hcd->self.controller)->vendor != PCI_VENDOR_ID_INTEL) {
> +		/* Last chance - if the controller has a custom tunnel_mode op, try that */
> +		if (xhci->tunnel_mode)
> +			return xhci->tunnel_mode(xhci_to_hcd(xhci), port->hcd_portnum);
> +		else
> +			return USB_LINK_UNKNOWN;
> +	}
>  
>  	offset = xhci_find_next_ext_cap(base, 0, XHCI_EXT_CAPS_INTEL_SPR_SHADOW);
>  
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 074d9c731639..dbaca694baa2 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -244,6 +244,8 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
>  		priv = hcd_to_xhci_priv(hcd);
>  		/* Just copy data for now */
>  		*priv = *priv_match;
> +
> +		xhci->tunnel_mode = priv->tunnel_mode;
>  	}
>  
>  	device_set_wakeup_capable(&pdev->dev, true);
> diff --git a/drivers/usb/host/xhci-plat.h b/drivers/usb/host/xhci-plat.h
> index 00751d851831..c5042766a486 100644
> --- a/drivers/usb/host/xhci-plat.h
> +++ b/drivers/usb/host/xhci-plat.h
> @@ -22,6 +22,7 @@ struct xhci_plat_priv {
>  	int (*suspend_quirk)(struct usb_hcd *);
>  	int (*resume_quirk)(struct usb_hcd *);
>  	int (*post_resume_quirk)(struct usb_hcd *);
> +	enum usb_link_tunnel_mode (*tunnel_mode)(struct usb_hcd *hcd, int portnum);

We should add a boolean tunnel_mode_override. When set, ->tunnel_mode()
is called before the standard xhci v1.2 ext_cap check. If the
->tunnel_mode() returns USB_LINK_UNKNOWN, go to the standard path. This
allows the quirk to selectively bypass or override it.

BR,
Thinh

>  };
>  
>  #define hcd_to_xhci_priv(h) ((struct xhci_plat_priv *)hcd_to_xhci(h)->priv)
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 091c82ca8ee2..118401a74244 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -4760,7 +4760,8 @@ static int xhci_update_device(struct usb_hcd *hcd, struct usb_device *udev)
>  	if (hcd->speed >= HCD_USB3 && !udev->parent->parent) {
>  		port = xhci->usb3_rhub.ports[udev->portnum - 1];
>  
> -		udev->tunnel_mode = xhci_port_is_tunneled(xhci, port);
> +		udev->tunnel_mode = xhci_port_tunnel_mode(xhci, port);
> +
>  		if (udev->tunnel_mode == USB_LINK_UNKNOWN)
>  			dev_dbg(&udev->dev, "link tunnel state unknown\n");
>  		else if (udev->tunnel_mode == USB_LINK_TUNNELED)
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 2d3941b5e1e3..a85968008a94 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1675,6 +1675,9 @@ struct xhci_hcd {
>  	struct list_head	regset_list;
>  
>  	void			*dbc;
> +
> +	enum usb_link_tunnel_mode (*tunnel_mode)(struct usb_hcd *hcd, int portnum);
> +
>  	/* platform-specific data -- must come last */
>  	unsigned long		priv[] __aligned(sizeof(s64));
>  };
> @@ -1981,7 +1984,7 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue, u16 wIndex,
>  int xhci_hub_status_data(struct usb_hcd *hcd, char *buf);
>  int xhci_find_raw_port_number(struct usb_hcd *hcd, int port1);
>  struct xhci_hub *xhci_get_rhub(struct usb_hcd *hcd);
> -enum usb_link_tunnel_mode xhci_port_is_tunneled(struct xhci_hcd *xhci,
> +enum usb_link_tunnel_mode xhci_port_tunnel_mode(struct xhci_hcd *xhci,
>  						struct xhci_port *port);
>  void xhci_hc_died(struct xhci_hcd *xhci);
>  
> 
> -- 
> 2.55.0
>