On Fri, Nov 12, 2021 at 4:23 PM Rafał Miłecki <zajec5@xxxxxxxxx> wrote:
>
> On 12.11.2021 23:18, Rob Herring wrote:
> > On Tue, Nov 2, 2021 at 10:22 AM Rafał Miłecki <zajec5@xxxxxxxxx> wrote:
> >>
> >> From: Rafał Miłecki <rafal@xxxxxxxxxx>
> >>
> >> During my work on MFD binding for Broadcom's TWD block I received
> >> comment from Rob saying that "syscon-reboot" should use "reg" property.
> >> I'm not sure if my understanding & implementation are correct so I'm
> >> sending this RFC.
> >>
> >> What bothers me is non-standard "reg" property usage. Treating it as a
> >> simple (unsigned) integer number means different logic when it comes to
> >> ranges.
> >
> > It shouldn't be. The idea is that 'reg' works like normal. See below.
> >
> >> Consider this example:
> >>
> >> timer@400 {
> >> compatible = "simple-mfd", "syscon";
> >> reg = <0x400 0x3c>;
> >> ranges;
> >
> > ranges = <0 0x400 0x100>; // Just guessing for size
> >
> >>
> >> #address-cells = <1>;
> >> #size-cells = <1>;
> >>
> >> reboot@434 {
> >
> > reboot@34
> >
> > Just reading 'reg' is fine, but really, Linux should be either getting
> > the translated address or have a function to get the offset from the
> > parent base. IOW, it should also work if you just changed 'reg' to
> > '<0x434 0x4>'.
>
> Are you aware of anyone working on support for getting translated
> address? Do you recall any efforts on implementing such a helper?
All the DT address functions give you translated addresses. It's the
latter that doesn't exist that I'm aware of offhand. It's just
of_address_to_resource() on the child and parent nodes and then
calculate the offset.
Rob
