linux-kernel - Re: [PATCH] of: When constructing the bus id consider assigned-addresses as well

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Message-ID: <20121201004948.GA3185@obsidianresearch.com>
Date:	Fri, 30 Nov 2012 17:49:48 -0700
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [PATCH] of: When constructing the bus id consider
 assigned-addresses as well

On Fri, Nov 30, 2012 at 09:48:05AM +0000, Grant Likely wrote:

> > If you attempt to stick a 'reg' in a block nested below a
> > 'device_type="pci"' the kernel throws lots of error messsages and
> > generates bad address mappings.
> 
> Have you added the appropriate #address-cells and #size-cells to the pci
> device node to go back to a non-pci addressing mode?
> assigned-addresses

Switching away from the 5 dword address format is not ideal
because then there is no way to specify the resource region (prefetch,
io, mmio) and mmio would have to be assumed.

> only makes sense in the pci-device node itself. reg should work for all
> nodes below that, and if it doesn't then it is a bug that we need to
> fix.

Okay.. but how should the DTS be constructed?

pcie_bus { // The PCI-E bus
   device_type = "pci";
   ranges = <5dw ranges>;
   #address-cells = <3>;
   #size-cells = <2>;
   soc_bridge { // The PCI-E device
      device_type = "pci";
      ranges = <5dw ranges>;

      soc_device { // Internal device
          assigned-address = <5dw regs>
      };
   };
};

This is what I have now, the soc_bridge PCI-E device is DTS modeled as
a PCI bridge - it has a ranges with its memory location, and the
children nodes are relative to those ranges. This would not be typical
for a non-bridge PCI-E device.

The reason for the 'assigned-address' requirement with the current
kernel code is the device_type=pci on soc_bridge. This makes
of_match_bus(parent) for soc_device return the PCI structure, which
has '.addresses = "assigned-addresses",'

So.. how would you like this to look?

Jason
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