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

Wei Huang
2024-09-05T15:08:45Z

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.

> PCI_TPH_CAP_ST_INT_VEC
> PCI_TPH_CAP_ST_DEV_SPEC

Will change

>
>> +#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.
>

Yes. In V1 review, Alex Williamson and Jonathan Cameron asked not to
change these definitions as they might be used by existing software.

>> +#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.