Re: [PATCH 2/5] thunderbolt: Verify PCIe adapters in detect state before setup PCIe tunnel

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Jan 27, 2026 at 12:06:03AM +0200, Gil Fine wrote:
> USB4 Connection Manager guide suggests making sure PCIe downstream and PCIe
> upstream adapter is in Detect state, before set up a PCIe tunnel.
> 
> Add this step by checking LTSSM field in ADP_PCIE_CS_0 to follow the CM
> guide more closely.
> 
> Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
> ---
>  drivers/thunderbolt/tb.h      |  2 ++
>  drivers/thunderbolt/tb_regs.h | 15 +++++++++++++++
>  drivers/thunderbolt/tunnel.c  | 17 +++++++++++++++++
>  drivers/thunderbolt/usb4.c    | 23 +++++++++++++++++++++++
>  4 files changed, 57 insertions(+)
> 
> diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
> index c2ff2069eb20..dbbbd2bd63f3 100644
> --- a/drivers/thunderbolt/tb.h
> +++ b/drivers/thunderbolt/tb.h
> @@ -1480,6 +1480,8 @@ int usb4_dp_port_allocate_bandwidth(struct tb_port *port, int bw);
>  int usb4_dp_port_requested_bandwidth(struct tb_port *port);
>  
>  int usb4_pci_port_set_ext_encapsulation(struct tb_port *port, bool enable);
> +int usb4_pci_port_check_ltssm_state(struct tb_port *port,
> +				    enum tb_pcie_ltssm_state ltssm);
>  
>  static inline bool tb_is_usb4_port_device(const struct device *dev)
>  {
> diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
> index c0bf136236e6..71bed02a6974 100644
> --- a/drivers/thunderbolt/tb_regs.h
> +++ b/drivers/thunderbolt/tb_regs.h
> @@ -473,10 +473,25 @@ struct tb_regs_port_header {
>  
>  /* PCIe adapter registers */
>  #define ADP_PCIE_CS_0				0x00
> +#define ADP_PCIE_CS_0_LTSSM_MASK		GENMASK(28, 25)
>  #define ADP_PCIE_CS_0_PE			BIT(31)
>  #define ADP_PCIE_CS_1				0x01
>  #define ADP_PCIE_CS_1_EE			BIT(0)
>  
> +enum tb_pcie_ltssm_state {
> +	TB_PCIE_LTSSM_DETECT		= 0x0,
> +	TB_PCIE_LTSSM_POLLING		= 0x1,
> +	TB_PCIE_LTSSM_CONFIG		= 0x2,
> +	TB_PCIE_LTSSM_CONFIG_IDLE	= 0x3,
> +	TB_PCIE_LTSSM_RECOVERY		= 0x4,
> +	TB_PCIE_LTSSM_RECOVERY_IDLE	= 0x5,
> +	TB_PCIE_LTSSM_L0		= 0x6,
> +	TB_PCIE_LTSSM_L1		= 0x7,
> +	TB_PCIE_LTSSM_L2		= 0x8,
> +	TB_PCIE_LTSSM_DISABLED		= 0x9,
> +	TB_PCIE_LTSSM_HOT_RESET		= 0xa,
> +};
> +
>  /* USB adapter registers */
>  #define ADP_USB3_CS_0				0x00
>  #define ADP_USB3_CS_0_V				BIT(30)
> diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
> index 28c1e5c062f3..72beaf99765f 100644
> --- a/drivers/thunderbolt/tunnel.c
> +++ b/drivers/thunderbolt/tunnel.c
> @@ -296,6 +296,22 @@ static inline void tb_tunnel_changed(struct tb_tunnel *tunnel)
>  			tunnel->src_port, tunnel->dst_port);
>  }
>  
> +static int tb_pci_pre_activate(struct tb_tunnel *tunnel)
> +{
> +	struct tb_port *down = tunnel->src_port;
> +	struct tb_port *up = tunnel->dst_port;
> +	int ret;
> +
> +	if (!tb_switch_is_usb4(down->sw) || !tb_switch_is_usb4(up->sw))

What if

 USB4 <-> TB3

I think we should do the same still, no?

> +		return 0;
> +
> +	ret = usb4_pci_port_check_ltssm_state(down, TB_PCIE_LTSSM_DETECT);
> +	if (ret)
> +		return ret;
> +
> +	return usb4_pci_port_check_ltssm_state(up, TB_PCIE_LTSSM_DETECT);
> +}
> +
>  static int tb_pci_set_ext_encapsulation(struct tb_tunnel *tunnel, bool enable)
>  {
>  	struct tb_port *port = tb_upstream_port(tunnel->dst_port->sw);
> @@ -511,6 +527,7 @@ struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
>  	if (!tunnel)
>  		return NULL;
>  
> +	tunnel->pre_activate = tb_pci_pre_activate;
>  	tunnel->activate = tb_pci_activate;
>  	tunnel->src_port = down;
>  	tunnel->dst_port = up;
> diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
> index 403a46aa35e5..706c9bc796e2 100644
> --- a/drivers/thunderbolt/usb4.c
> +++ b/drivers/thunderbolt/usb4.c
> @@ -3145,3 +3145,26 @@ int usb4_pci_port_set_ext_encapsulation(struct tb_port *port, bool enable)
>  	return tb_port_write(port, &val, TB_CFG_PORT,
>  			     port->cap_adap + ADP_PCIE_CS_1, 1);
>  }
> +
> +/**
> + * usb4_pci_port_check_ltssm_state() - Checks the LTSSM state of PCIe adapter
> + * @port: PCIe adapter
> + * @ltssm: PCIe adapter LTSSM state as encoded in &enum tb_pcie_ltssm_state
> + *
> + * Return:
> + * * %0 - If LTSSM state of @port is as expected @state.
> + * * %-ETIMEDOUT - The @ltssm state was not reached within the given timeout.
> + * * Negative errno - Other failure occurred.
> + */
> +int usb4_pci_port_check_ltssm_state(struct tb_port *port,
> +				    enum tb_pcie_ltssm_state ltssm)
> +{
> +	u32 val = FIELD_PREP(ADP_PCIE_CS_0_LTSSM_MASK, ltssm);
> +
> +	if (!tb_port_is_pcie_down(port) && !tb_port_is_pcie_up(port))
> +		return -EINVAL;
> +
> +	return usb4_port_wait_for_bit(port, port->cap_adap + ADP_PCIE_CS_0,
> +				      ADP_PCIE_CS_0_LTSSM_MASK, val, 500,
> +				      USB4_PORT_DELAY);
> +}
> -- 
> 2.43.0