On Thu, Jan 19, 2023 at 10:41 AM Simon Glass <s...@chromium.org> wrote: > > Hi Abdellatif, > > On Thu, 19 Jan 2023 at 09:32, Abdellatif El Khlifi > <abdellatif.elkhl...@arm.com> wrote: > > > > On Wed, Jan 18, 2023 at 08:59:32AM -0500, Tom Rini wrote: > > > On Wed, Jan 18, 2023 at 01:46:54PM +0000, Sudeep Holla wrote: > > > > On Wed, Jan 18, 2023 at 12:49 PM Tom Rini <tr...@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. > > > > Hi Simon, Tom, > > > > The FF-A transport is a SW bus and is not associated to any HW peripheral or > > undiscoverable base address. > > > > There is only 1 way of discovering the FF-A bus and it's through the FF-A SW > > interfaces. The FF-A spec [1] describes this in details. > > Can you add a DT node for the 'FF-A SW interfaces' and attach some > sort of top-level driver to that? Perhaps simple-bus, or your own > thing? You don't need to add compatible strings for subnodes (devices > that are discoverable within that).
We already have that. It's just called 'arm,psci'. FF-A is not the top-level thing. SMCCC is. That's unfortunately called PSCI in DT because SMCCC grew out of PSCI. Evolution is ugly... It's like this: SMCCC +--PSCI +--TRNG +--FF-A +--SCMI (sometimes) +--OP-TEE +--...Whatever Arm comes up with next... Rob
