Re: [PATCH v7 2/5] PCI/TPH: Add requester/completer type helpers

[Alex Williamson <alex@shazbot.org>]

On Thu, 11 Jun 2026 09:11:17 -0700
Zhiping Zhang <zhipingz@meta.com> wrote:

> Add pcie_tph_enabled_req_type() so drivers can query the enabled TPH
> requester mode without reaching into pci_dev internals.
> 
> Add pcie_tph_completer_type() so drivers that publish TPH metadata for
> a device acting as a completer can gate on the "TPH Completer
> Supported" field of Device Capabilities 2 (bits 13:12,
> PCI_EXP_DEVCAP2_TPH_COMP_MASK) rather than reusing requester-side
> state. Fold the reserved 0b10 encoding into NONE so callers only see
> the defined values.
> 
> This keeps pci_dev::tph_req_type and the completer-capability decode
> inside the PCI/TPH code and provides !CONFIG_PCIE_TPH stubs for
> callers.
> 
> Signed-off-by: Zhiping Zhang <zhipingz@meta.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>

This is carrying forward an ack for v6, where half the interface here
was dropped and changed shape.  Thanks,

Alex

> ---
>  drivers/pci/tph.c       | 43 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci-tph.h |  8 ++++++++
>  2 files changed, 51 insertions(+)
> 
> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
> index 91145e8d9d95..4fe076bba953 100644
> --- a/drivers/pci/tph.c
> +++ b/drivers/pci/tph.c
> @@ -174,6 +174,49 @@ u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)
>  }
>  EXPORT_SYMBOL(pcie_tph_get_st_table_loc);
>  
> +/**
> + * pcie_tph_enabled_req_type - Return the device's enabled TPH requester type
> + * @pdev: PCI device to query
> + *
> + * Return: PCI_TPH_REQ_DISABLE, PCI_TPH_REQ_TPH_ONLY or PCI_TPH_REQ_EXT_TPH.
> + */
> +u8 pcie_tph_enabled_req_type(struct pci_dev *pdev)
> +{
> +	return pdev->tph_req_type;
> +}
> +EXPORT_SYMBOL(pcie_tph_enabled_req_type);
> +
> +/**
> + * pcie_tph_completer_type - Return the device's TPH Completer support
> + * @pdev: PCI device to query
> + *
> + * Reads the "TPH Completer Supported" field (bits 13:12) of Device
> + * Capabilities 2. The reserved 0b10 encoding is folded into
> + * "not supported" so callers only need to compare against the three
> + * defined values.
> + *
> + * Return: one of %PCI_EXP_DEVCAP2_TPH_COMP_NONE,
> + *         %PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY or
> + *         %PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH.
> + */
> +u8 pcie_tph_completer_type(struct pci_dev *pdev)
> +{
> +	u32 reg;
> +
> +	if (pcie_capability_read_dword(pdev, PCI_EXP_DEVCAP2, &reg))
> +		return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
> +
> +	switch (FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg)) {
> +	case PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY:
> +		return PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY;
> +	case PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH:
> +		return PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH;
> +	default:
> +		return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
> +	}
> +}
> +EXPORT_SYMBOL(pcie_tph_completer_type);
> +
>  /*
>   * Return the size of ST table. If ST table is not in TPH Requester Extended
>   * Capability space, return 0. Otherwise return the ST Table Size + 1.
> diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
> index be68cd17f2f8..7743af6fe432 100644
> --- a/include/linux/pci-tph.h
> +++ b/include/linux/pci-tph.h
> @@ -9,6 +9,8 @@
>  #ifndef LINUX_PCI_TPH_H
>  #define LINUX_PCI_TPH_H
>  
> +#include <linux/pci_regs.h>
> +
>  /*
>   * According to the ECN for PCI Firmware Spec, Steering Tag can be different
>   * depending on the memory type: Volatile Memory or Persistent Memory. When a
> @@ -30,6 +32,8 @@ void pcie_disable_tph(struct pci_dev *pdev);
>  int pcie_enable_tph(struct pci_dev *pdev, int mode);
>  u16 pcie_tph_get_st_table_size(struct pci_dev *pdev);
>  u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev);
> +u8 pcie_tph_enabled_req_type(struct pci_dev *pdev);
> +u8 pcie_tph_completer_type(struct pci_dev *pdev);
>  #else
>  static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
>  					unsigned int index, u16 tag)
> @@ -41,6 +45,10 @@ static inline int pcie_tph_get_cpu_st(struct pci_dev *dev,
>  static inline void pcie_disable_tph(struct pci_dev *pdev) { }
>  static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
>  { return -EINVAL; }
> +static inline u8 pcie_tph_enabled_req_type(struct pci_dev *pdev)
> +{ return PCI_TPH_REQ_DISABLE; }
> +static inline u8 pcie_tph_completer_type(struct pci_dev *pdev)
> +{ return PCI_EXP_DEVCAP2_TPH_COMP_NONE; }
>  #endif
>  
>  #endif /* LINUX_PCI_TPH_H */