linux-kernel - Re: [PATCH V4 02/12] PCI: Add TPH related register definition

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Message-ID: <20240904195254.GA344807@bhelgaas>
Date: Wed, 4 Sep 2024 14:52:54 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Wei Huang <wei.huang2@....com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, netdev@...r.kernel.org,
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Subject: Re: [PATCH V4 02/12] PCI: Add TPH related register definition

On Thu, Aug 22, 2024 at 03:41:10PM -0500, Wei Huang wrote:
> Linux has some basic, but incomplete, definition for the TPH Requester
> capability registers. Also the definitions of TPH Requester control
> register and TPH Completer capability, as well as the ST fields of
> MSI-X entry, are missing. Add all required definitions to support TPH
> without changing the existing Linux UAPI.

>  /* TPH Requester */
>  #define PCI_TPH_CAP		4	/* capability register */
> -#define  PCI_TPH_CAP_LOC_MASK	0x600	/* location mask */
> -#define   PCI_TPH_LOC_NONE	0x000	/* no location */
> -#define   PCI_TPH_LOC_CAP	0x200	/* in capability */
> -#define   PCI_TPH_LOC_MSIX	0x400	/* in MSI-X */
> -#define PCI_TPH_CAP_ST_MASK	0x07FF0000	/* ST table mask */
> -#define PCI_TPH_CAP_ST_SHIFT	16	/* ST table shift */
> -#define PCI_TPH_BASE_SIZEOF	0xc	/* size with no ST table */
> +#define  PCI_TPH_CAP_NO_ST	0x00000001 /* No ST Mode Supported */
> +#define  PCI_TPH_CAP_INT_VEC	0x00000002 /* Interrupt Vector Mode Supported */
> +#define  PCI_TPH_CAP_DEV_SPEC	0x00000004 /* Device Specific Mode Supported */

I think these modes should all include "ST" to clearly delineate
Steering Tags from the Processing Hints.  E.g.,

  PCI_TPH_CAP_ST_NO_ST       or maybe PCI_TPH_CAP_ST_NONE
  PCI_TPH_CAP_ST_INT_VEC
  PCI_TPH_CAP_ST_DEV_SPEC

> +#define  PCI_TPH_CAP_EXT_TPH	0x00000100 /* Ext TPH Requester Supported */
> +#define  PCI_TPH_CAP_LOC_MASK	0x00000600 /* ST Table Location */
> +#define   PCI_TPH_LOC_NONE	0x00000000 /* Not present */
> +#define   PCI_TPH_LOC_CAP	0x00000200 /* In capability */
> +#define   PCI_TPH_LOC_MSIX	0x00000400 /* In MSI-X */

These are existing symbols just being tidied, so can't really add "ST"
here unless we just add aliases.  Since they're just used internally,
not by drivers, I think they're fine as-is.

> +#define  PCI_TPH_CAP_ST_MASK	0x07FF0000 /* ST Table Size */
> +#define  PCI_TPH_CAP_ST_SHIFT	16	/* ST Table Size shift */
> +#define PCI_TPH_BASE_SIZEOF	0xc	/* Size with no ST table */
> +
> +#define PCI_TPH_CTRL		8	/* control register */
> +#define  PCI_TPH_CTRL_MODE_SEL_MASK	0x00000007 /* ST Mode Select */
> +#define   PCI_TPH_NO_ST_MODE		0x0 /* No ST Mode */
> +#define   PCI_TPH_INT_VEC_MODE		0x1 /* Interrupt Vector Mode */
> +#define   PCI_TPH_DEV_SPEC_MODE		0x2 /* Device Specific Mode */

These are also internal, but they're new and I think they should also
include "ST" to match the CAP #defines.

Even better, maybe we only add these and use them for both CAP and
CTRL since they're defined with identical values.