[PATCH v3 0/2] rng: Provide a RNG based on the RISC-V Zkr ISA extension

[Simon Glass]

Hi,

On Tue, 7 Nov 2023 at 15:38, Tom Rini <trini at konsulko.com> wrote:
>
> On Tue, Nov 07, 2023 at 10:27:50PM +0000, Conor Dooley wrote:
> > On Tue, Nov 07, 2023 at 05:10:23PM -0500, Tom Rini wrote:
> >
> >
> > > further clarify or not
> > > the RISC-V ISA thing that's elsewhere in this thread (and part of the
> > > kernel, not a U-Boot thing).
> >
> > TBH, this a bit fragmented across threads, and as someone that hasn't
> > been following it it's a bit difficult to tell exactly what is being
> > asked for. Would someone be able to ask it as a direct question?
>
> Sorry for being unclear, and thanks for asking. What I think the U-Boot
> community would like to know is, what is the device-tree based way to
> know if a RISC-V platform has the Zbb extensions and so the RNG opcodes,
> similar (in concept at least?) to the ARMv8.5 RNG feature.

Some more details (sorry) from your friendly devicetree and driver
model maintainer:

- U-Boot models hardware (and other things) as devices in driver model [1]
- U-Boot requires devices to be in the devicetree, with very limited
exceptions [2]
- Where multiple devices exist in a uclass, it is desirable to be able
to number them [3]
- Similarly it is useful to be able select a particular device, e.g.
with a phandle [4]
- U-Boot uses devicetree for configuration as it has no userspace

Regards,
Simon

[1] https://u-boot.readthedocs.io/en/latest/develop/driver-model/index.html
[2] https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#platform-data
[3] https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#device-sequence-numbers
[4] https://u-boot.readthedocs.io/en/latest/api/dm.html?highlight=phandle#c.of_find_node_by_phandle