Re: [PATCH V3 3/6] platform/x86/intel: Move intel_pmt from MFD to Auxiliary Bus

Andy Shevchenko
2021-12-13T18:29:00Z

On Mon, Dec 13, 2021 at 09:59:18AM -0800, David E. Box wrote:
> Intel Platform Monitoring Technology (PMT) support is indicated by presence
> of an Intel defined PCIe Designated Vendor Specific Extended Capabilities
> (DVSEC) structure with a PMT specific ID. The current MFD implementation
> creates child devices for each PMT feature, currently telemetry, watcher,
> and crashlog. However DVSEC structures may also be used by Intel to
> indicate support for other features. The Out Of Band Management Services
> Module (OOBMSM) uses DVSEC to enumerate several features, including PMT.
> In order to support them it is necessary to modify the intel_pmt driver to
> handle the creation of the child devices more generically. To that end,
> modify the driver to create child devices for any VSEC/DVSEC features on
> supported devices (indicated by PCI ID). Additionally, move the
> implementation from MFD to the Auxiliary bus. VSEC/DVSEC features are
> really multifunctional PCI devices, not platform devices as MFD was
> designed for. Auxiliary bus gives more flexibility by allowing the
> definition of custom structures that can be shared between associated
> auxiliary devices and the parent device. Also, rename the driver from
> intel_pmt to intel_vsec to better reflect the purpose.
>
> This series also removes the current runtime pm support which was not
> complete to begin with. None of the current devices require runtime pm.
> However the support will be replaced when a device is added that requires
> it.

...

> +static bool intel_vsec_walk_dvsec(struct pci_dev *pdev, unsigned long quirks)
> +{
> + bool have_devices = false;
> + int pos = 0;
> +
> + do {
> + struct intel_vsec_header header;
> + u32 table, hdr;
> + u16 vid;
> + int ret;
> +
> + pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_DVSEC);
> + if (!pos)
> + break;
> +
> + pci_read_config_dword(pdev, pos + PCI_DVSEC_HEADER1, &hdr);
> + vid = PCI_DVSEC_HEADER1_VID(hdr);
> + if (vid != PCI_VENDOR_ID_INTEL)
> + continue;
> +
> + /* Support only revision 1 */
> + header.rev = PCI_DVSEC_HEADER1_REV(hdr);
> + if (header.rev != 1) {
> + dev_info(&pdev->dev, "Unsupported DVSEC revision %d\n", header.rev);
> + continue;
> + }
> +
> + header.length = PCI_DVSEC_HEADER1_LEN(hdr);
> +
> + pci_read_config_byte(pdev, pos + INTEL_DVSEC_ENTRIES, &header.num_entries);
> + pci_read_config_byte(pdev, pos + INTEL_DVSEC_SIZE, &header.entry_size);
> + pci_read_config_dword(pdev, pos + INTEL_DVSEC_TABLE, &table);
> +
> + header.tbir = INTEL_DVSEC_TABLE_BAR(table);
> + header.offset = INTEL_DVSEC_TABLE_OFFSET(table);
> +
> + pci_read_config_dword(pdev, pos + PCI_DVSEC_HEADER2, &hdr);
> + header.id = PCI_DVSEC_HEADER2_ID(hdr);
> +
> + ret = intel_vsec_add_dev(pdev, &header, quirks);
> + if (ret)
> + continue;
> +
> + have_devices = true;
> + } while (true);
> +
> + return have_devices;
> +}
> +
> +static bool intel_vsec_walk_vsec(struct pci_dev *pdev, unsigned long quirks)
> +{
> + bool have_devices = false;
> + int pos = 0;
> +
> + do {
> + struct intel_vsec_header header;
> + u32 table, hdr;
> + int ret;
> +
> + pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_VNDR);
> + if (!pos)
> + break;
> +
> + pci_read_config_dword(pdev, pos + PCI_VNDR_HEADER, &hdr);
> +
> + /* Support only revision 1 */
> + header.rev = PCI_VNDR_HEADER_REV(hdr);
> + if (header.rev != 1) {
> + dev_info(&pdev->dev, "Unsupported VSEC revision %d\n", header.rev);
> + continue;
> + }
> +
> + header.id = PCI_VNDR_HEADER_ID(hdr);
> + header.length = PCI_VNDR_HEADER_LEN(hdr);
> +
> + /* entry, size, and table offset are the same as DVSEC */
> + pci_read_config_byte(pdev, pos + INTEL_DVSEC_ENTRIES, &header.num_entries);
> + pci_read_config_byte(pdev, pos + INTEL_DVSEC_SIZE, &header.entry_size);
> + pci_read_config_dword(pdev, pos + INTEL_DVSEC_TABLE, &table);
> +
> + header.tbir = INTEL_DVSEC_TABLE_BAR(table);
> + header.offset = INTEL_DVSEC_TABLE_OFFSET(table);
> +
> + ret = intel_vsec_add_dev(pdev, &header, quirks);
> + if (ret)
> + continue;
> +
> + have_devices = true;
> + } while (true);
> +
> + return have_devices;
> +}

I'm wondering if it makes sense to refactor each of the above to something like

int intel_vsec_extract_vsec(...)
{
...
}

static bool intel_vsec_walk_dvsec(struct pci_dev *pdev, unsigned long quirks)
{
bool have_devices = false;
int pos;

while ((pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_DVSEC))) {
if (intel_vsec_extract_vsec())
continue;

have_devices = true;
}

return have_devices;
}

Either way, it may be worth to convert infinite loops to ones with the clear
exit condition.

...

> + /*
> + * Driver cleanup handled by intel_vsec_remove_aux() which is added
> + * to the pci device as a devm action

PCI

Grammatical period at the end.

> + */

--
With Best Regards,
Andy Shevchenko