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.