Re: [PATCH v3 06/13] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors

Rob Herring
2025-05-14T15:42:50Z

On Tue, May 13, 2025 at 03:14:56PM -0700, Ricardo Neri wrote:
> On Mon, May 12, 2025 at 10:32:24AM -0500, Rob Herring wrote:
> > On Tue, May 06, 2025 at 08:23:39PM -0700, Ricardo Neri wrote:
> > > On Tue, May 06, 2025 at 09:10:22AM +0200, Krzysztof Kozlowski wrote:
> > > > On Mon, May 05, 2025 at 10:16:10PM GMT, Ricardo Neri wrote:
> > > > > > If this is a device, then compatibles specific to devices. You do not
> > > > > > get different rules than all other bindings... or this does not have to
> > > > > > be binding at all. Why standard reserved-memory does not work for here?
> > > > > >
> > > > > > Why do you need compatible in the first place?
> > > > >
> > > > > Are you suggesting something like this?
> > > > >
> > > > > reserved-memory {
> > > > > # address-cells = <2>;
> > > > > # size-cells = <1>;
> > > > >
> > > > > wakeup_mailbox: wakeupmb@fff000 {
> > > > > reg = < 0x0 0xfff000 0x1000>
> > > > > }
> > > > >
> > > > > and then reference to the reserved memory using the wakeup_mailbox
> > > > > phandle?
> > > >
> > > > Yes just like every other, typical reserved memory block.
> > >
> > > Thanks! I will take this approach and drop this patch.
> >
> > If there is nothing else to this other than the reserved region, then
> > don't do this. Keep it like you had. There's no need for 2 nodes.
>
> Thank you for your feedback!
>
> I was planning to use one reserved-memory node and inside of it a child
> node to with a `reg` property to specify the location and size of the
> mailbox. I would reference to that subnode from the kernel code.
>
> IIUC, the reserved-memory node is only the container and the actual memory
> regions are expressed as child nodes.
>
> I had it like that before, but with a `compatible` property that I did not
> need.
>
> Am I missing anything?

Without a compatible, how do you identify which reserved region is the
wakeup mailbox? Before you say node name, those are supposed to be
generic though we failed to enforce anything for /reserved-memory child
nodes.

Rob