Re: [PATCH v2 07/10] ARM: tegra: pcie: Add device tree support

[Mitch Bradley <wmb@firmworks.com>]

On 6/12/2012 9:46 AM, Stephen Warren wrote:
> On 06/12/2012 01:10 PM, Mitch Bradley wrote:
>> On 6/12/2012 7:20 AM, Thierry Reding wrote:
> ...
>>> I came up with the following alternative:
>>>
>>> 	pci {
>>> 		compatible = "nvidia,tegra20-pcie";
>>> 		reg =<0x80003000 0x00000800   /* PADS registers */
>>> 		       0x80003800 0x00000200   /* AFI registers */
>>> 		       0x80004000 0x00100000   /* configuration space */
>>> 		       0x80104000 0x00100000   /* extended configuration space */
>>> 		       0x80400000 0x00010000   /* downstream I/O */
>>> 		       0x90000000 0x10000000   /* non-prefetchable memory */
>>> 		       0xa0000000 0x10000000>; /* prefetchable memory */
>>> 		interrupts =<0 98 0x04   /* controller interrupt */
>>> 		              0 99 0x04>; /* MSI interrupt */
>>> 		status = "disabled";
>>>
>>> 		ranges =<0x80000000 0x80000000 0x00002000   /* 2 root ports */
>>> 			  0x80004000 0x80004000 0x00100000   /* configuration space */
>>> 			  0x80104000 0x80104000 0x00100000   /* extended configuration space */
>>> 			  0x80400000 0x80400000 0x00010000   /* downstream I/O */
>>> 			  0x90000000 0x90000000 0x10000000   /* non-prefetchable memory */
>>> 			  0xa0000000 0xa0000000 0x10000000>; /* prefetchable memory */
>>>
>>> 		#address-cells =<1>;
>>> 		#size-cells =<1>;
>>>
>>> 		port@80000000 {
>>> 			reg =<0x80000000 0x00001000>;
>>> 			status = "disabled";
>>> 		};
>>>
>>> 		port@80001000 {
>>> 			reg =<0x80001000 0x00001000>;
>>> 			status = "disabled";
>>> 		};
>>> 	};
>>>
>>> The "ranges" property can probably be cleaned up a bit, but the most
>>> interesting part is the port@ children, which can simply be enabled in board
>>> DTS files by setting the status property to "okay". I find that somewhat more
>>> intuitive to the variant with an "enable-ports" property.
>>>
>>> What do you think of this?
>>
>> The problem is that children of a PCI-ish bus have specific expectations
>> about the parent address format - the standard 3-address-cell PCI
>> addressing.  So making a PCI bus node - even if it is PCIe - with 1
>> address cell is a problem.
>
> Couldn't you put the #address-cells=<3>  underneath each port node, and
> put any PCIe devices there rather than under the main PCIe controller
> node? I'm not sure how the interrupt mapping table etc. would work in
> that case, but that seems to solve the addressing issue.

Yes, that would work just fine, and in fact would be preferable, if a 
"root port" is essentially an independent PCI bus.  The parent of those 
root ports should not be named "pci", though, as it is not in itself a 
PCI bus.  It could be called "pcis".

>
>