On Thursday 11 September 2014 14:11:05 Phil Edworthy wrote:

On 10 September 2014 19:20, Arnd wrote:

quoted

On Tuesday 09 September 2014 12:20:54 Catalin Marinas wrote:

quoted

We can assume that if a domain is not specified and there is a single
top level PCIe node, the domain defaults to 0. Are there any arm32
platforms that require multiple domains (and do not specify a number in
the DT)?

In theory, I think all of them could work with a single domain, but then
you need to partition the bus number space between the host controllers,
so you have the exact same situation that you either need to make up
random bus numbers or put them in DT.

Using multiple domains is way cleaner for this, even if we have to
make up the numbers.

Maybe this is a stupid question, but why would you want to specify the domain
in the DT at all? Doesn't every instance of a driver imply a separate domain?

See Jason Gunthorpe's latest reply on the topic. In short, the domain is
visible to user space and we want it to be stable across boots when
user configuration refers to devices by domain:bus:device:function
numbers.

	Arnd