On Wed, Nov 08, 2023 at 12:29:03AM +0000, Conor Dooley wrote: > On Tue, Nov 07, 2023 at 06:23:05PM -0500, Tom Rini wrote: [snip] > > Thanks. Setting aside Simon's follow-up, this is what I was looking for. > > We might have to wait for Heinrich to return from the conference to have > > time to look at how to utilize the above and see what we can do from > > there. > > I did read that, but I don't think most of it is relevant to the binding > itself. His five things were: > | - U-Boot models hardware (and other things) as devices in driver model [1] > > This I think should be satisfied. The Zkr CSR is a property of the CPU, > and shouldn't have its own DT node IMO. Is it problematic for U-Boot to > populate multiple devices for its driver model based on one DT node? > I know in Linux that I can create devices using something like > platform_device_register(), does U-Boot have a similar facility? > https://elixir.bootlin.com/linux/latest/source/drivers/base/platform.c#L767 > > | - 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] > > I'm not sure really how this one ties in. Do you need a number for each > CPU that supports Zkr, since a system may be heterogeneous? I think that > how you treat things like that is beyond communicating support via DT > though, IMO the job of the DT is just to tell U-Boot on which CPUs it > can access the seed CSR. > > | - Similarly it is useful to be able select a particular device, e.g. > | with a phandle [4] > > I suppose a phandle to the CPU would work in this case. > > | - U-Boot uses devicetree for configuration as it has no userspace
I mean, the reason I was setting aside Simon's question is that in my mind, we (U-Boot) need to think about what we're declaring as a MUST because the constant feedback that we get is "No, why does that need to get added to DT? Can't you just use ... ?". So I do find your answers above enlightening in that regard. -- Tom
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