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

Bjorn Helgaas
2024-09-05T16:41:30Z

On Thu, Sep 05, 2024 at 10:08:33AM -0500, Wei Huang wrote:
> On 9/4/24 14:52, Bjorn Helgaas wrote:
> >> -#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
>
> Can I keep "NO_ST" instead of switching over to "ST_NONE"? First, it
> matches with PCIe spec. Secondly, IMO "ST_NONE" implies no ST support at
> all.

Sure. Does PCI_TPH_CAP_ST_NO_ST work for you? That follows the same
PCI_TPH_CAP_ST_* pattern as below.

> > PCI_TPH_CAP_ST_INT_VEC
> > PCI_TPH_CAP_ST_DEV_SPEC
>
> Will change

> >> +#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.
>
> Can you elaborate here? In CTRL register, "ST Mode Select" is defined as
> a 2-bit field. The possible values are 0, 1, 2. But in CAP register, the
> modes are individual bit masked. So I cannot use CTRL definitions in CAP
> register directly unless I do shifting.

Oops, sorry, I thought they were the same values, but they're not, so
ignore this comment.