Re: [PATCH v3] PCI: Unify ECAM constants in native PCI Express drivers

[Rob Herring <robh@kernel.org>]

On Thu, Oct 1, 2020 at 5:02 PM Krzysztof Wilczyński <kw@linux.com> wrote:
>
> Unify ECAM-related constants into a single set of standard constants
> defining memory address shift values for the byte-level address that can
> be used when accessing the PCI Express Configuration Space, and then
> move native PCI Express controller drivers to use newly introduced
> definitions retiring any driver-specific ones.
>
> The ECAM ("Enhanced Configuration Access Mechanism") is defined by the
> PCI Express specification (see PCI Express Base Specification, Revision
> 5.0, Version 1.0, Section 7.2.2, p. 676), thus most hardware should
> implement it the same way.  Most of the native PCI Express controller
> drivers define their ECAM-related constants, many of these could be
> shared, or use open-coded values when setting the .bus_shift field of
> the struct pci_ecam_ops.
>
> All of the newly added constants should remove ambiguity and reduce the
> number of open-coded values, and also correlate more strongly with the
> descriptions in the aforementioned specification (see Table 7-1
> "Enhanced Configuration Address Mapping", p. 677).
>
> There is no change to functionality.
>
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
> ---
> Changes in v3:
>   Updated commit message wording.
>   Updated regarding custom ECAM bus shift values and concerning PCI base
>   configuration space access for Type 1 access.
>   Refactored rockchip_pcie_rd_other_conf() and rockchip_pcie_wr_other_conf()
>   and removed the "busdev" variable.
>   Removed surplus "relbus" variable from nwl_pcie_map_bus() and
>   xilinx_pcie_map_bus().
>   Renamed the PCIE_ECAM_ADDR() macro to PCIE_ECAM_OFFSET().
>
> Changes in v2:
>   Use PCIE_ECAM_ADDR macro when computing ECAM address offset, but drop
>   PCI_SLOT and PCI_FUNC macros from the PCIE_ECAM_ADDR macro in favour
>   of using a single value for the device/function.
>
>  drivers/pci/controller/dwc/pcie-al.c        |  8 ++----
>  drivers/pci/controller/dwc/pcie-hisi.c      |  4 +--
>  drivers/pci/controller/pci-host-generic.c   |  4 +--
>  drivers/pci/controller/pci-thunder-ecam.c   |  2 +-
>  drivers/pci/controller/pci-thunder-pem.c    | 13 +++++++--
>  drivers/pci/controller/pci-xgene.c          | 13 +++++++--
>  drivers/pci/controller/pcie-rockchip-host.c | 27 +++++++++--------
>  drivers/pci/controller/pcie-rockchip.h      |  8 +-----
>  drivers/pci/controller/pcie-tango.c         |  2 +-
>  drivers/pci/controller/pcie-xilinx-nwl.c    |  9 ++----
>  drivers/pci/controller/pcie-xilinx.c        | 11 ++-----
>  drivers/pci/ecam.c                          |  4 +--
>  include/linux/pci-ecam.h                    | 32 +++++++++++++++++++++

What about vmd which I mentioned? I also found iproc and brcmstb are
ECAM (well, same shifts, but indirect addressing).

[...]

> +/*
> + * Enhanced Configuration Access Mechanism (ECAM)
> + *
> + * N.B. This is a non-standard platform-specific ECAM bus shift value.  For
> + * standard values defined in the PCI Express Base Specification see
> + * include/linux/pci-ecam.h.
> + */
> +#define XGENE_PCIE_ECAM_BUS_SHIFT      16

Isn't this just CAM? Though perhaps CAM on PCIe is not standard...

For CAM, there's also tegra, ftpci100, mvebu, and versatile. I think
I'd drop CAM from this patch and do all of those in a separate patch.

Rob

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