On 30 October 2015 at 18:28, Rob Herring <robh+dt@xxxxxxxxxx> wrote: > On Thu, Oct 29, 2015 at 9:01 AM, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote: >> +Valid Secure world properties: >> + >> +- secure-status : specifies whether the device is present and usable >> + in the secure world. The combination of this with "status" allows >> + the various possible combinations of device visibility to be >> + specified: >> + status = "okay"; // visible in S and NS > > I assume neither property present or both okay also mean the same. > > status = "okay"; secure-status = "okay"; > > We should be explicit. Yes; status defaults to "okay" (presumably this is listed in the overal DT binding spec somewhere), and secure-status defaults to "same as status, which might in turn be defaulted". We can list the complete set of options (neither present, both 'okay', status not present but secure-status present, etc), though it gets a bit long-winded, especially if we later add more secure- properties (they'd all have to have verbiage about "if not present, same as non-prefixed property; if both not present, both take the default the non-prefixed property takes if it's not present; if prefixed property not present, it defaults to same as non-prefixed property", which we already say in the introductory section). Still, for just status it would be easy enough to add a couple of lines: + status = "okay"; secure-status = "okay"; // ditto + secure-status = "okay"; // ditto + // neither explicitly defined: ditto (Do you want the full set of 9 options you get from multiplying out "okay" vs "disabled" vs not-set for each property?) >> + status = "disabled"; secure-status = "okay"; // S-only >> + status = "okay"; secure-status = "disabled"; // NS-only > > In HKG when we discussed this, 'status = "secure"' was the proposal. > That would be simpler: > > S world can use "okay" or "secure" > NS world can use "okay" or no property. > > That leaves out the case of disabled in S and enabled for NS. We could > want that for s/w reasons, but can we have h/w like that? It's perfectly possible to design hardware like that (though I can't think of a reason to do so offhand). I think it's the desire to be able to describe all the possible valid h/w combinations that brought us to this secure- prefix design. Plus it extends nicely to cover other possibilities as we need it; for instance "device A is at S-0x10000 but NS-0x20000" can be done by specifying a device like: status = "okay"; secure-status = "okay"; reg = < 0x20000 0x1000 >; secure-regs = < 0x10000 0x1000 >; (apologies if I've messed the syntax up there). Just going for 'status=secure' would deal with the immediate requirement, but my preference is for a description that lets us describe all the possible configurations, not just the ones we think are common, and secure-* is a neat way of doing that (IIRC it was Grant's suggestion; speaking of whom, I just noticed I forgot to cc him on the original patch). thanks -- PMM -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
