[PATCH 24/32] pci: PCIe driver for Marvell Armada 370/XP systems

[Thierry Reding]

On Thu, Mar 07, 2013 at 06:05:33PM -0600, Rob Herring wrote:
> On 03/07/2013 02:47 PM, Thierry Reding wrote:
[...]
> > In a nutshell (since some of the context isn't quoted anymore) the
> > problem that we're trying to solve is that some of the embedded SoCs
> > require per-root-port registers for configuration. The PCI DT
> > specification doesn't make any provisions for this. A few alternatives
> > have been discussed so far:
> 
> I'm not sure I follow. This is different than the host controller
> registers? Why would this not just be multiple entries in the reg property?

Well the register regions are per root-port. On Tegra20 there's 2 of
them, Tegra30 has 3 and if I understand correctly Marvell can have up to
10 (!). Adding all of them to the reg property of the host controller
could work but it needs some way to match the reg entry to the root port
similar to option 1 below.

Adding a property in the root port nodes seems like a cleaner and more
accurate representation of the hardware to me, but if that's not
acceptable perhaps we need to bite the bullet and add the code to look
the registers up from the parent's reg property.

Thierry

> > 	1) Use a "regs" property outside of the root port nodes with
> > 	   some mechanism to index into them from within the root port
> > 	   nodes. Conceptually somewhat like this:
> > 
> > 		pcie-controller {
> > 			...
> > 			regs = <0x80000000 0x00001000
> > 			        0x80001000 0x00001000>;
> > 
> > 			pci at 0,1 {
> > 				...
> > 				port-index = <0>;
> > 			};
> > 
> > 			pci at 0,2 {
> > 				...
> > 				port-index = <1>;
> > 			};
> > 		};
> > 
> > 	2) Use a "regs" property inside of the root part nodes, along
> > 	   the following lines:
> > 
> > 		pcie-controller {
> > 			...
> > 			pci at 0,1 {
> > 				...
> > 				reg = <0x00000800 0 0 0 0>;
> > 
> > 				regs = <0x80000000 0x00001000>;
> > 			};
> > 
> > 			pci at 0,2 {
> > 				...
> > 				reg = <0x00001000 0 0 0 0>;
> > 
> > 				regs = <0x80001000 0x00001000>;
> > 			};
> > 		};
> > 
> > 	3) Repurpose the "assigned-addresses" property to achieve the
> > 	   same. This should work out-of-the-box but isn't a good fit
> > 	   because it conflicts with the OF PCI specification which
> > 	   defines this property to contain the addresses assigned to
> > 	   the base address registers.
> > 
> > Options 1 and 2 above require changes to the OF core to allow proper
> > address translation, but the changes shouldn't be very big.
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