Re: [PATCH V8 9/9] pci, acpi: ARM64 support for ACPI based generic PCI host controller

[Arnd Bergmann]

On Monday, May 30, 2016 5:14:22 PM CEST Tomasz Nowicki wrote:
> +       bsz = 1 << pci_generic_ecam_ops.bus_shift;
> +       cfgres.start = root->mcfg_addr + bus_res->start * bsz;
> +       cfgres.end = cfgres.start + resource_size(bus_res) * bsz - 1;
> +       cfgres.flags = IORESOURCE_MEM;
> +       cfg = pci_ecam_create(&root->device->dev, &cfgres, bus_res,
> +                             &pci_generic_ecam_ops);
> +       if (IS_ERR(cfg)) {
> +               pr_err("%04x:%pR error %ld mapping CAM\n", seg, bus_res,
> +                      PTR_ERR(cfg));
> +               return PTR_ERR(cfg);
> +       }
> +
> +       ri->cfg = cfg;
> +       return 0;
> +}

I wonder if we could do this a little simpler and just put a pointer
to the mmconfig space into struct pci_host_bridge, and then have a trivial
map_bus function alongside pci_generic_config_read/pci_generic_config_write.

As this code is specific to arch/arm64, we don't need any of the complexity
of drivers/pci/ecam.c, which basically only exists to work around the
limited virtual address space of 32-bit machines.

	Arnd