Re: [RFC PATCH 1/3] pci, acpi: Match PCI config space accessors against platfrom specific ECAM quirks.

Arnd Bergmann
2016-06-02T12:32:54Z

On Thursday, June 2, 2016 2:07:43 PM CEST Tomasz Nowicki wrote:
> On 02.06.2016 13:42, Arnd Bergmann wrote:
> > On Thursday, June 2, 2016 10:41:01 AM CEST Tomasz Nowicki wrote:
> >> +struct pci_ecam_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> >> +{
> >> + int bus_num = root->secondary.start;
> >> + int domain = root->segment;
> >> + struct pci_cfg_fixup *f;
> >> +
> >> + if (!mcfg_table)
> >> + return &pci_generic_ecam_ops;
> >> +
> >> + /*
> >> + * Match against platform specific quirks and return corresponding
> >> + * CAM ops.
> >> + *
> >> + * First match against PCI topology <domain:bus> then use OEM ID and
> >> + * OEM revision from MCFG table standard header.
> >> + */
> >> + for (f = __start_acpi_mcfg_fixups; f < __end_acpi_mcfg_fixups; f++) {
> >> + if ((f->domain == domain || f->domain == PCI_MCFG_DOMAIN_ANY) &&
> >> + (f->bus_num == bus_num || f->bus_num == PCI_MCFG_BUS_ANY) &&
> >> + (!strncmp(f->oem_id, mcfg_table->header.oem_id,
> >> + ACPI_OEM_ID_SIZE)) &&
> >> + (f->oem_revision == mcfg_table->header.oem_revision))
> >> + return f->ops;
> >> + }
> >> + /* No quirks, use ECAM */
> >> + return &pci_generic_ecam_ops;
> >> +}
> >> +
> >> int pci_mcfg_lookup(struct acpi_pci_root *root)
> >
> > Can you explain the use of pci_ecam_ops instead of pci_ops here?
> >
>
> I wanted to get associated bus_shift and use it to setup configuration
> region properly before calling pci_ecam_create. Please see next patch.
>

I see. It feels really odd to do it this way though, since having a
nonstandard bus_shift essentially means not using anything resembling
ECAM to start with.

I realize that a lot of the host bridges are not ECAM, but because
of this, it would be more logical to have their own pci_ops instead
of pci_ecam_ops.

Arnd