linux-kernel - Re: [PATCH] PCI: generic: Add support for Cavium ThunderX PCIe root complexes.

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Date:	Tue, 15 Sep 2015 19:40:03 +0100
From:	Will Deacon <will.deacon@....com>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH] PCI: generic: Add support for Cavium ThunderX PCIe root
 complexes.

On Sat, Sep 12, 2015 at 01:07:19AM +0100, David Daney wrote:
> From: David Daney <david.daney@...ium.com>
> 
> The config space for external PCIe root complexes on some Cavium
> ThunderX SoCs is very similar to CAM and ECAM, but differs in the
> shift values that have to be applied to the bus and devfn numbers to
> compose that address window offset.  These root complexes also have
> the interesting property that there is no root bridge, so the standard
> manner of limiting scanning to only the first device doesn't work.  We
> can use the standard pci-host-generic driver if we make a minor
> addition to handle these differences, so we...
> 
> Add a mapping function for ThunderX PCIe root complexes with a bus
> shift of 24 and devfn shift of 16.  Ignore accesses for devices other
> than the first device on the primary bus.
> 
> Document the whole thing in devicetree/bindings/pci/host-generic-pci.txt
> 
> Signed-off-by: David Daney <david.daney@...ium.com>
> ---
> 
> This patch depends on the set I recently sent:
> https://lkml.org/lkml/2015/9/11/764
> 
>  .../devicetree/bindings/pci/host-generic-pci.txt   |  5 +++-
>  drivers/pci/host/pci-host-generic.c                | 29 ++++++++++++++++++++++
>  2 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.txt b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
> index daa6942..51cc1d1 100644
> --- a/Documentation/devicetree/bindings/pci/host-generic-pci.txt
> +++ b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
> @@ -16,7 +16,10 @@ Properties of the host controller node:
>  
>  - compatible     : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
>                     depending on the layout of configuration space (CAM vs
> -                   ECAM respectively).
> +                   ECAM respectively). Also supported is
> +                   "cavium,pci-host-thunder-pem" which has bus:devfn:reg in
> +                   bits 24:16:0 respectively of the PCI config space address
> +                   window.

It's probably easier to read and maintain if we reword this as a list of
property + comment rather than continue the freeform text.

Other than that, I'm fine with special-casing your accessors if need-be.

Will
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