Re: [PATCH V7 07/11] pci, acpi: Handle ACPI companion assignment.

["Rafael J. Wysocki" <rafael@kernel.org>]

On Tue, May 10, 2016 at 5:19 PM, Tomasz Nowicki <tn@semihalf.com> wrote:
> This patch provides a way to set the ACPI companion in PCI code.
> We define acpi_pci_set_companion() to set the ACPI companion pointer and
> call it from PCI core code. The function is stub for now.
>
> Signed-off-by: Jayachandran C <jchandra@broadcom.com>
> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> ---
>  drivers/pci/probe.c      | 2 ++
>  include/linux/pci-acpi.h | 4 ++++
>  2 files changed, 6 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 8004f67..fb0b752 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -12,6 +12,7 @@
>  #include <linux/slab.h>
>  #include <linux/module.h>
>  #include <linux/cpumask.h>
> +#include <linux/pci-acpi.h>
>  #include <linux/pci-aspm.h>
>  #include <linux/aer.h>
>  #include <linux/acpi.h>
> @@ -2141,6 +2142,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>         bridge->dev.parent = parent;
>         bridge->dev.release = pci_release_host_bridge_dev;
>         dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
> +       acpi_pci_set_companion(bridge);

Yes, we'll probably add something similar here.

Do I think now is the right time to do that?  No.

>         error = pcibios_root_bridge_prepare(bridge);
>         if (error) {
>                 kfree(bridge);
> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> index 09f9f02..1baa515 100644
> --- a/include/linux/pci-acpi.h
> +++ b/include/linux/pci-acpi.h
> @@ -111,6 +111,10 @@ static inline void acpi_pci_add_bus(struct pci_bus *bus) { }
>  static inline void acpi_pci_remove_bus(struct pci_bus *bus) { }
>  #endif /* CONFIG_ACPI */
>
> +static inline void acpi_pci_set_companion(struct pci_host_bridge *bridge)
> +{
> +}
> +
>  static inline int acpi_pci_bus_domain_nr(struct pci_bus *bus)
>  {
>         return 0;
> --

Honestly, to me it looks like this series is trying very hard to avoid
doing any PCI host bridge configuration stuff from arch/arm64/
although (a) that might be simpler and (b) it would allow us to
identify the code that's common between *all* architectures using ACPI
support for host bridge configuration and to move *that* to a common
place later.  As done here it seems to be following the "ARM64 is
generic and the rest of the world is special" line which isn't really
helpful.