linux-kernel - Re: tracking of PCI address space

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Date:	Wed, 8 Apr 2009 16:53:52 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Ira Snyder <iws@...o.caltech.edu>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, linux-pci@...r.kernel.org,
	Benjamin Herrenschmidt <benh@....ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux/PPC Development <linuxppc-dev@...abs.org>
Subject: Re: tracking of PCI address space


On Apr 8, 2009, at 4:49 PM, Ira Snyder wrote:

> On Wed, Apr 08, 2009 at 03:53:55PM -0500, Kumar Gala wrote:
>> I was wondering if we have anything that tracks regions associated  
>> with
>> the "inbound" side of a pci_bus.
>>
>> What I mean is on embedded PPC we have window/mapping registers for  
>> both
>> inbound (accessing memory on the SoC) and outbound (access PCI device
>> MMIO, IO etc).  The combination of the inbound & outbound convey what
>> exists in the PCI address space vs CPU physical address space (and  
>> how to
>> map from one to the other).  Today in the PPC land we only attach
>> outbound windows to the pci_bus.  So technically the inbound side
>> information (like what subset of physical memory is visible on the  
>> PCI
>> bus) seems to be lost.
>>
>
> To the best of my knowledge there is no API to set inbound windows in
> Linux. I've been implementing a virtio-over-PCI driver which needs the
> inbound windows. I set them up myself during driver probe, using
> get_immrbase() to get the IMMR registers. This board is a PCI Slave /
> Agent, it doesn't even have PCI support compiled into the kernel.

I'm not concerned explicitly about setting up inbound windows, its  
more about have a consistent view of the PCI address space which may  
be different from the CPU physical address space.

I'm working on code to actually setup the inbound windows on 85xx/86xx  
class devices (based on dma-ranges property in the device tree).  As I  
was thinking about this I realized that the send of ranges/dma-ranges  
in the .dts and what we map to outbound vs inbound changes if we an  
agent or host.

- k
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