linux-kernel - Re: [RFC PATCH RESEND v2] of/pci: Provide support for parsing PCI DT ranges property

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Date:	Fri, 01 Mar 2013 09:13:34 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Andrew Murray <Andrew.Murray@....com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Liviu Dudau <Liviu.Dudau@....com>
Subject: Re: [RFC PATCH RESEND v2] of/pci: Provide support for parsing PCI
 DT ranges property

On 03/01/2013 06:23 AM, Andrew Murray wrote:
> This patch factors out common implementations patterns to reduce overall kernel
> code and provide a means for host bridge drivers to directly obtain struct
> resources from the DT's ranges property without relying on architecture specific
> DT handling. This will make it easier to write archiecture independent host bridge
> drivers and mitigate against further duplication of DT parsing code.
> 
> This patch can be used in the following way:
> 
> 	struct of_pci_range_iter iter;
> 	for_each_of_pci_range(&iter, np) {
> 
> 		//directly access properties of the address range, e.g.:
> 		//iter.pci_space, iter.pci_addr, iter.cpu_addr, iter.size or
> 		//iter.flags
> 
> 		//alternatively obtain a struct resource, e.g.:
> 		//struct resource res;
> 		//range_iter_fill_resource(iter, np, res);
> 	}
> 
> Additionally the implementation takes care of adjacent ranges and merges them
> into a single range (as was the case with powerpc and microblaze).
> 
> The modifications to microblaze, mips and powerpc have not been tested.
> 
> v2:
>   This follows on from suggestions made by Grant Likely
>   (marc.info/?l=linux-kernel&m=136079602806328)
> 
> Signed-off-by: Andrew Murray <Andrew.Murray@....com>
> Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> ---
>  arch/microblaze/pci/pci-common.c |  100 +++++++++++--------------------------
>  arch/mips/pci/pci.c              |   44 ++++-------------
>  arch/powerpc/kernel/pci-common.c |   93 ++++++++++-------------------------
>  drivers/of/address.c             |   54 ++++++++++++++++++++
>  include/linux/of_address.h       |   30 +++++++++++
>  5 files changed, 151 insertions(+), 170 deletions(-)

The thing is that this still leaves pci_process_bridge_OF_ranges
basically identical for microblaze and powerpc which is really what
needs to be moved out to common code. Obviously, struct pci_controller
vs. struct pci_sys_data on ARM is an issue, but they all have
fundamentally the same data.

All these common fields should be in a common PCI controller struct.
Perhaps introducing this with just what you need would work. Depending
how invasive moving those fields to a new struct is, you could have a
wrapper that just copies/translates the fields to the arch specific struct.

There's also things like ioremap of the i/o range. ARM uses a fixed
virtual address, so we need to do something different. Just returning
the i/o cpu_addr and moving the ioremap out of this function would solve
that.

Rob

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