On Thu, Jul 17, 2025 at 11:33:54AM -0700, Dan Williams wrote:
> PCIe 6.2 Section 7.7.9 Device 3 Extended Capability Structure,
> enumerates new link capabilities and status added for Gen 6 devices. One
> of the link details enumerated in that register block is the "Segment
> Captured" status in the Device Status 3 register. That status is
> relevant for enabling IDE (Integrity & Data Encryption) whereby
> Selective IDE streams can be limited to a given Requester ID range
> within a given segment.
>
> If a device has captured its Segment value then it knows that PCIe Flit
> Mode is enabled via all links in the path that a configuration write
> traversed. IDE establishment requires that "Segment Base" in
> IDE RID Association Register 2 (PCIe 6.2 Section 7.9.26.5.4.2) be
> programmed if the RID association mechanism is in effect.
>
> When / if IDE + Flit Mode capable devices arrive, the PCI core needs to
> setup the segment base when using the RID association facility, but no
> known deployments today depend on this.
>
> Cc: Lukas Wunner <lukas@xxxxxxxxx>
> Cc: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Samuel Ortiz <sameo@xxxxxxxxxxxx>
> Cc: Alexey Kardashevskiy <aik@xxxxxxx>
> Cc: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> ---
> drivers/pci/probe.c | 12 ++++++++++++
> include/linux/pci.h | 1 +
> include/uapi/linux/pci_regs.h | 7 +++++++
> 3 files changed, 20 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index e19e7a926423..9ed25035a06d 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2271,6 +2271,17 @@ int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
> return 0;
> }
>
> +static void pci_dev3_init(struct pci_dev *pdev)
> +{
> + u16 cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DEV3);
> + u32 val = 0;
> +
> + if (!cap)
> + return;
> + pci_read_config_dword(pdev, cap + PCI_DEV3_STA, &val);
> + pdev->fm_enabled = !!(val & PCI_DEV3_STA_SEGMENT);
> +}
> +
> /**
> * pcie_relaxed_ordering_enabled - Probe for PCIe relaxed ordering enable
> * @dev: PCI device to query
> @@ -2625,6 +2636,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
> pci_doe_init(dev); /* Data Object Exchange */
> pci_tph_init(dev); /* TLP Processing Hints */
> pci_rebar_init(dev); /* Resizable BAR */
> + pci_dev3_init(dev); /* Device 3 capabilities */
> pci_ide_init(dev); /* Link Integrity and Data Encryption */
>
> pcie_report_downtraining(dev);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 0e5703fad0f6..a7353df51fea 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -444,6 +444,7 @@ struct pci_dev {
> unsigned int pasid_enabled:1; /* Process Address Space ID */
> unsigned int pri_enabled:1; /* Page Request Interface */
> unsigned int tph_enabled:1; /* TLP Processing Hints */
> + unsigned int fm_enabled:1; /* Flit Mode (segment captured) */
> unsigned int is_managed:1; /* Managed via devres */
> unsigned int is_msi_managed:1; /* MSI release via devres installed */
> unsigned int needs_freset:1; /* Requires fundamental reset */
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 1b991a88c19c..2d49a4786a9f 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -751,6 +751,7 @@
> #define PCI_EXT_CAP_ID_NPEM 0x29 /* Native PCIe Enclosure Management */
> #define PCI_EXT_CAP_ID_PL_32GT 0x2A /* Physical Layer 32.0 GT/s */
> #define PCI_EXT_CAP_ID_DOE 0x2E /* Data Object Exchange */
> +#define PCI_EXT_CAP_ID_DEV3 0x2F /* Device 3 Capability/Control/Status */
> #define PCI_EXT_CAP_ID_IDE 0x30 /* Integrity and Data Encryption */
> #define PCI_EXT_CAP_ID_PL_64GT 0x31 /* Physical Layer 64.0 GT/s */
> #define PCI_EXT_CAP_ID_MAX PCI_EXT_CAP_ID_PL_64GT
> @@ -1227,6 +1228,12 @@
> /* Deprecated old name, replaced with PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE */
> #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE
>
> +/* Device 3 Extended Capability */
> +#define PCI_DEV3_CAP 0x4 /* Device 3 Capabilities Register */
> +#define PCI_DEV3_CTL 0x8 /* Device 3 Control Register */
> +#define PCI_DEV3_STA 0xc /* Device 3 Status Register */
> +#define PCI_DEV3_STA_SEGMENT 0x8 /* Segment Captured (end-to-end flit-mode detected) */
> +
> /* Compute Express Link (CXL r3.1, sec 8.1.5) */
> #define PCI_DVSEC_CXL_PORT 3
> #define PCI_DVSEC_CXL_PORT_CTL 0x0c
> --
> 2.50.1
>
