Re: [PATCH v3 2/4] usb: xhci: Honor PORTSC.TM if valid

[Thinh Nguyen]

On Tue, Sep 01, 2026, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
> 
> Currently, the only way for the USB core to determine whether the link
> is native or tunneled is via an Intel vendor-specific Extended
> Capability.
> 
> The XHCI specification v1.2 and newer expose a common ext_cap,
> indicating whether BIT(2) of PORTSC can be interpreted as the tunneling
> status.
> 
> Make use of that and fall back to the existing Intel-specific path if
> the ext_cap is absent.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
> ---
>  drivers/usb/host/xhci-ext-caps.h |  3 +++
>  drivers/usb/host/xhci-hub.c      | 11 ++++++++++-
>  drivers/usb/host/xhci-port.h     |  3 ++-
>  drivers/usb/host/xhci.c          |  8 ++++++++
>  drivers/usb/host/xhci.h          |  1 +
>  5 files changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-ext-caps.h b/drivers/usb/host/xhci-ext-caps.h
> index 22e53a750e2a..af7d624cd38e 100644
> --- a/drivers/usb/host/xhci-ext-caps.h
> +++ b/drivers/usb/host/xhci-ext-caps.h
> @@ -66,6 +66,9 @@
>  #define XHCI_HLC               (1 << 19)
>  #define XHCI_BLC               (1 << 20)
>  
> +/* USB3 tunneling support capability - section 7.11 */
> +#define XHCI_USB3_TUNNELING_SUPPORTED	BIT(16)
> +
>  /* Intel SPR shadow capability */
>  #define XHCI_INTEL_SPR_ESS_PORT_OFFSET  0x8ac4	/* SuperSpeed port control */
>  #define XHCI_INTEL_SPR_TUNEN	BIT(4)		/* Tunnel mode enabled */
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 470bafe1802b..80f07bd5081d 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -769,8 +769,17 @@ enum usb_link_tunnel_mode xhci_port_is_tunneled(struct xhci_hcd *xhci,
>  	struct usb_hcd *hcd;
>  	void __iomem *base;
>  	u32 offset;
> +	u32 val;
>  
> -	/* Don't try and probe this capability for non-Intel hosts */
> +	if (xhci->portsc_tunnel_reporting) {
> +		val = xhci_portsc_readl(port);
> +		if (val & PORT_TM)
> +			return USB_LINK_TUNNELED;
> +
> +		return USB_LINK_NATIVE;
> +	}
> +
> +	/* 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)
> diff --git a/drivers/usb/host/xhci-port.h b/drivers/usb/host/xhci-port.h
> index 889b5fb0fcd8..215c9cadbc34 100644
> --- a/drivers/usb/host/xhci-port.h
> +++ b/drivers/usb/host/xhci-port.h
> @@ -5,7 +5,8 @@
>  #define PORT_CONNECT	(1 << 0)
>  /* true: port enabled */
>  #define PORT_PE		(1 << 1)
> -/* bit 2 reserved and zeroed */
> +/* true: port is tunneling traffic over USB4 */
> +#define PORT_TM		(1 << 2)
>  /* true: port has an over-current condition */
>  #define PORT_OC		(1 << 3)
>  /* true: port reset signaling asserted */
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index a9e47e178c28..5fb78613a993 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -5433,9 +5433,11 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
>  	 * quirks
>  	 */
>  	struct device		*dev = hcd->self.sysdev;
> +	void __iomem		*base;
>  	int			retval;
>  	u32			hcs_params1;
>  	u32			hc_capbase;
> +	u32			tunnel_cap;
>  
>  	/* Accept arbitrarily long scatter-gather lists */
>  	hcd->self.sg_tablesize = ~0;
> @@ -5456,6 +5458,7 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
>  	mutex_init(&xhci->mutex);
>  	xhci->main_hcd = hcd;
>  	xhci->cap_regs = hcd->regs;
> +	base = &xhci->cap_regs->hc_capbase;
>  	hc_capbase = readl(&xhci->cap_regs->hc_capbase);
>  	if (hc_capbase == U32_MAX) {
>  		xhci_warn(xhci, "Host controller not accessible, removed?\n");
> @@ -5473,6 +5476,11 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
>  	xhci->hcc_params = readl(&xhci->cap_regs->hcc_params);
>  	if (xhci->hci_version > 0x100)
>  		xhci->hcc_params2 = readl(&xhci->cap_regs->hcc_params2);
> +	tunnel_cap = xhci_find_next_ext_cap(base, 0, XHCI_EXT_CAPS_USB3_TUNNELING);
> +	if (tunnel_cap) {
> +		xhci->portsc_tunnel_reporting =
> +			!!(readl(base + tunnel_cap) & XHCI_USB3_TUNNELING_SUPPORTED);
> +	}
>  
>  	xhci->dma_mask_bits = 64;
>  	xhci->max_slots = min(FIELD_GET(HCS_SLOTS_MASK, hcs_params1), MAX_HC_SLOTS);
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index c7bfa7f028d3..480fcbac4525 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1662,6 +1662,7 @@ struct xhci_hcd {
>  	/* cached extended protocol port capabilities */
>  	struct xhci_port_cap	*port_caps;
>  	unsigned int		num_port_caps;
> +	bool			portsc_tunnel_reporting;
>  	/* Compliance Mode Recovery Data */
>  	struct timer_list	comp_mode_recovery_timer;
>  	u32			port_status_u0;
> 
> -- 
> 2.55.0
> 

Reviewed-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>

Thanks,
Thinh