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

Rob Herring
2020-10-02T15:21:14Z

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