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

Tom Rini
2023-01-18T13:59:41Z

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On Wed, Jan 18, 2023 at 01:46:54PM +0000, Sudeep Holla wrote:
> 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.

To be clear, if the position is that "this is what everyone else will
use, really" then yes, we'll follow this in U-Boot.

--
Tom

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