Hi Bjorn,

On Fri, Feb 5, 2016 at 5:49 AM, Bjorn Helgaas [off-list ref] wrote:

Hi Jayachandran,

On Fri, Jan 29, 2016 at 02:35:40PM +0530, Jayachandran C wrote:

quoted

Add a simple ACPI based PCI host controller under config option
ACPI_PCI_HOST_GENERIC. This is done by providing an implementation
of pci_acpi_scan_root().

The pci_mmcfg_list handling is done by the ACPI code, so we keep a
reference to the pci_mmcfg_region in sysdata. The ECAM region will
be already mapped, so map_bus can be implemented by using the
virt pointer for the pci_mmcfg_region. pci_generic_config_read
and pci_generic_config_write are used for config space read/write.

Also, we provide implementations of raw_pci_read and raw_pci_write
hat are needed by ACPI based on the pci_mmcfg_list.

pci_acpi_set_companion() and acpi_pci_get_segment() are defined
using sysdata of generic ACPI host controller so that PCI domain
and ACPI companion are set in PCI code rather than platform code.

This code is currently enabled only for ARM64.

Signed-off-by: Jayachandran C <redacted>
---
 drivers/acpi/Kconfig         |   8 ++
 drivers/acpi/Makefile        |   1 +
 drivers/acpi/pci_host_acpi.c | 186 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-acpi.h     |  17 ++++
 4 files changed, 212 insertions(+)
 create mode 100644 drivers/acpi/pci_host_acpi.c

I'm speaking a little bit out of turn here, because this is ACPI code,
but I'm confused about pci_host_acpi.c.  We already have pci_root.c,
which is *supposed* to be arch-independent.  I know pci_root.c is
crufty and could be improved, but it does work today on x86 and ia64,
and it handles some generic things that pci_host_acpi.c does not,
e.g., _OSC, NUMA, host bridge hotplug, etc.

I'd really like to see pci_root.c improved so it could work on x86,
ia64, and arm64.  I'm sure that was probably the first thing you
tried, so likely there are issues there.  Are they insurmountable?

pci_root.c leaves the implementation of pci_acpi_scan_root() to the
architecture. Implementing pci_acpi_scan_root needs a
pci_acpi_root_ops instance and a pci_ops instance and related functions.
The architecture is also expected to implement raw_pci_read and
raw_pci_write.

pci_host_acpi.c is a generic implementation of these using a sysdata
pointing to acpi_pci_root_info, and using a pointer to the pci_mmcfg_region
to access ECAM area, Maybe I can rename this file to
pci_acpi_host_generic.c to reflect this better.

arm64 is the only user of this generic implementation now. The config
option CONFIG_ACPI_PCI_HOST_GENERIC has to be set on the
architecture that chooses to use this generic code instead of its own
implementation.

JC.
{Sorry if the formatting is wrong, using webmail due to internal IT changes]