Re: [RESEND v13 01/25] CXL/PCI: Move CXL DVSEC definitions into uapi/linux/pci_regs.h

Jonathan Cameron
2025-11-04T17:50:35Z

On Tue, 4 Nov 2025 11:02:41 -0600
Terry Bowman <terry.bowman@amd.com> wrote:

> The CXL DVSECs are currently defined in cxl/core/cxlpci.h. These are not
> accessible to other subsystems. Move these to uapi/linux/pci_regs.h.
>
> Change DVSEC name formatting to follow the existing PCI format in
> pci_regs.h. The current format uses CXL_DVSEC_XYZ and the CXL defines must
> be changed to be PCI_DVSEC_CXL_XYZ to match existing pci_regs.h. Leave
> PCI_DVSEC_CXL_PORT* defines as-is because they are already defined and may
> be in use by userspace application(s).
>
> Update existing usage to match the name change.
>
> Update the inline documentation to refer to latest CXL spec version.
>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>
Hi Terry,

A few minor things inline.

I'll assume you'll resolve those for next version and as they are
really minor
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b14dd064006c..53a49bb32514 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5002,7 +5002,9 @@ static bool cxl_sbr_masked(struct pci_dev *dev)
> if (!dvsec)
> return false;
>
> - rc = pci_read_config_word(dev, dvsec + PCI_DVSEC_CXL_PORT_CTL, &reg);
> + rc = pci_read_config_word(dev,
> + dvsec + PCI_DVSEC_CXL_PORT_CTL,
> + &reg);
Looks like left over from before where that define got longer?
Shouldn't still be here given the two lines are (I think?) identical other
than some premature line wrapping.
> if (rc || PCI_POSSIBLE_ERROR(reg))
> return false;
>
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 07e06aafec50..279b92f01d08 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1244,9 +1244,64 @@
> /* 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
>
> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
> -#define PCI_DVSEC_CXL_PORT 3
> -#define PCI_DVSEC_CXL_PORT_CTL 0x0c
> -#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR 0x00000001
> +/* Compute Express Link (CXL r3.2, sec 8.1)
Follow local comment style.
/*
* Compute Express Link (CXL r3.2, sec 8.1)
*...

> + *
> + * Note that CXL DVSEC id 3 and 7 to be ignored when the CXL link state
> + * is "disconnected" (CXL r3.2, sec 9.12.3). Re-enumerate these
> + * registers on downstream link-up events.
> + */

> +/* CXL 3.2 8.1.8: PCIe DVSEC for Flex Bus Port */
> +#define PCI_DVSEC_CXL_FLEXBUS_PORT 7
> +#define PCI_DVSEC_CXL_FLEXBUS_STATUS_OFFSET 0xE

I wonder if you should keep the _PORT in the naming for consistency.
These are also new defines rather than moves / renames. I wonder if it
makes sense to bury them in this patch. Instead bring them in where they
are used? That will also make it more obvious why only a fairly random
looking subset of this structure is used.

> +#define PCI_DVSEC_CXL_FLEXBUS_STATUS_CACHE_MASK _BITUL(0)
> +#define PCI_DVSEC_CXL_FLEXBUS_STATUS_MEM_MASK _BITUL(2)
> +
> +/* CXL 3.2 8.1.9: Register Locator DVSEC */
> +#define PCI_DVSEC_CXL_REG_LOCATOR 8
> +#define PCI_DVSEC_CXL_REG_LOCATOR_BLOCK1_OFFSET 0xC
> +#define PCI_DVSEC_CXL_REG_LOCATOR_BIR_MASK __GENMASK(2, 0)
> +#define PCI_DVSEC_CXL_REG_LOCATOR_BLOCK_ID_MASK __GENMASK(15, 8)
> +#define PCI_DVSEC_CXL_REG_LOCATOR_BLOCK_OFF_LOW_MASK __GENMASK(31, 16)
>
> #endif /* LINUX_PCI_REGS_H */