[PATCH 03/14] bus: mvebu-mbus: Introduce device tree binding

Ezequiel Garcia
2013-06-08T17:29:21Z

On Fri, Jun 07, 2013 at 01:44:30PM -0600, Jason Gunthorpe wrote:
> On Fri, Jun 07, 2013 at 09:10:35PM +0200, Arnd Bergmann wrote:
> > On Friday 07 June 2013, Ezequiel Garcia wrote:
> > > + np = of_find_matching_node(NULL, of_mvebu_mbus_ids);
> > > + if (!np) {
> > > + pr_err("could not find a matching SoC family\n");
> > > + return -ENODEV;
> > > + }
> > > +
> > > + of_id = of_match_node(of_mvebu_mbus_ids, np);
> > > + mbus_state.soc = of_id->data;
> > > +
> > > + if (of_address_to_resource(np, 0, &mbuswins_res)) {
> > > + pr_err("cannot get MBUS register address\n");
> > > + return -EINVAL;
> > > + }
> > > +
> > > + if (of_address_to_resource(np, 1, &sdramwins_res)) {
> > > + pr_err("cannot get SDRAM register address\n");
> > > + return -EINVAL;
> > > + }
> >
> > Just an idea to make this more regular: Since the internal-regs can no longer
> > be regarded as a fixed location, we might want to use the same "ranges" property
> > mechanism for resolving the internal regs as we use for everything else.
> >
> > This would imply that the device node this driver binds to would actually
> > end up being a child of the bus itself, which then goes on to modify the
> > ranges property of its parent node. Does that make sense?
>
> We have a minimum requirement that the bootloader setup internal regs,
> so the minimum required DT bindings is going to be this:
>
> mbus {
> compatible = ...
> ranges = <INTERNAL_REGS_MAP_ID 0xf1000000 0x100000>;
> reg = <0xf1000xxx ...>; // MBUS regs block
> #address/size-cells...
>
> internal-regs {
> ranges = <0 INTERNAL_REGS_MAP_ID 0x100000>;
> }
> }
>

... and the above is the way its done in my proposal,
with INTERNAL_REGS_MAP_ID = 0x0.

> ie the ranges should never be empty.
>
> Discovery of the address of the mbus control registers is via the reg
> property on its own node (which is untranslated), and all other
> internal regs blocks will automatically translate as they are supposed
> to (Thomas's work to make internal regs 0xd/0xf1 relies on this, AFAIK)
>
> INTERNAL_REGS_MAP_ID is an invalid target ID value, defined to mean
> the internal registers target. 0xFFFFFFFF is a better choice for this
> than 0, because 0xFFFFFFFF is never going to be a valid target id, it
> is too large.
>

I agree, using 0x0 was not a good choice. I'll change that.

Thanks both for the feedback!
--
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering