Re: [PATCH v8 03/10] arm_ffa: introduce Arm FF-A low-level driver

[Sudeep Holla <sudeep.holla@arm.com>]

On Wed, Jan 18, 2023 at 12:49 PM Tom Rini <trini@konsulko.com> wrote:

>
> I guess the problem comes down to, can we have one discovery method that
> everyone shares, or do we have to let everyone invent a new discovery
> method every time?


No one needs to invent any discovery method every time if the firmware
specification
provides one and as Rob mentioned many times in the thread, all new firmware
specification must provide one and we are trying to make sure that is
the case with all new
specs from Arm.


> FF-A, Op-tee, U-Boot, coreboot, barebox (and
> everyone else I'm unintentionally forgetting) could just discover these
> things via device tree.


I leave that to the individual projects to decide and agree but
fundamentally if
the specification provides a way to discover, not sure why we are even
discussing
an alternative method here.


> Or, we could all write our own code to perform
> the discovery.


For what reason ? I can understand if there is no discovery mechanism but
that's not the
case in $subject.


> And when RISC-V comes along with similar functionality,
> we could probe their device tree and see they've implemented the same
> concept, but a little differently, but still have the discovery portion
> be in the device tree. To which it sounds like your answer is "not in
> the device tree".
>

I see U-boot seem to have made a decision to create DT node for each and
everything
that needs to be added to DM which seems bit unfortunate but I don't
understand the
history/motive/background for it but I respect the decision if it is
already made.

These firmware interfaces are standard on all Arm platforms and can be
discovered
based on PSCI/SMCCC. Not using the same and use DT node needs unnecessary
addition of DT nodes for all the f/w i/f on all the platforms that need the
support when
one can be just discovered.

Sorry for the sudden appearance on this thread, I was avoiding getting into
this but thought
I will at least express my opinion and also the way the firmware
specifications from Arm is
expected to be evolved from now on. With that I will leave it to you and
other U-boot
maintainers and the community in general to decide the right course in this
case.