On Wed, 8 Nov 2023 at 14:57, Rob Herring <robh@xxxxxxxxxx> wrote: > > On Wed, Nov 8, 2023 at 5:38 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > On Tue, 7 Nov 2023 at 19:07, Rob Herring <robh@xxxxxxxxxx> wrote: > > > > > > > > > All of this: > > > > > > > > > On Mon, 16 Oct 2023 at 15:54, Simon Glass <sjg@xxxxxxxxxxxx> wrote: > > > > > > > > > > It is not specific to EDK2. Imagine this boot sequence: > > > > > > > > > > - Platform Init (U-Boot) starts up > > > > > - U-Boot uses its platform knowledge to sets some ACPI tables and put > > > > > various things in memory > > > > > - U-Boot sets up some runtime code and data for the OS > > > > > - U-Boot jumps to the Tianocore payload ** > > > > > - Payload (Tianocore) wants to know where the ACPI tables are, for example > > > > > - Tianocore needs to provide boot services to the OS, so needs to know > > > > > the memory map, etc. > > > > > > > > > > ** At this point we want to use DT to pass the required information. > > > > > > > > > > Of course, Platform Init could be coreboot or Tianocore or some > > > > > strange private binary. Payload could be U-Boot or something else. > > > > > That is the point of this effort, to build interoperability. > > > > > > [...] > > > > > > > > Perhaps the problem here is that Linux has tied itself up in knots > > > > > with its EFI stuff and DT fixups and what-not. But this is not that. > > > > > It is a simple handoff between two pieces of firmware, Platform Init > > > > > and Payload. It has nothing to do with the OS. With Tianocore they are > > > > > typically combined, but with this usage they are split, and we can > > > > > swap out one project for another on either side of the DT interface. > > > > > > Is perhaps the clearest description of the problem you want to solve. > > > It's clearly related to EFI though not the interface to the OS. IIRC, > > > "platform init" and "payload" are terms in the UEFI spec, right? > > > > No they are not. This is from the universal payload specification that > > is being drafted here > > > > https://universalpayload.github.io/spec/index.html > > > > but the UEFI specification does not use this terminology. > > Then I'm confused as to what this is: > > https://uefi.org/specs/PI/1.8/index.html > The PI and UEFI specifications are both maintained by the UEFI forum. The UEFI specification covers external APIs for firmware implementations, i.e., the OS visible interface and the public API for UEFI device drivers that are not tightly integrated with system firmware (for example, the GPU boot time driver in the ROM of an add-in card) The UEFI forum's PI spec describes system firmware internals, and defines the SEC, PEI DXE and BDS boot phases, among other things. It is possible to implement UEFI without PI (which is what uboot does, for instance), but Tianocore/EDK2 is the reference implementation for both PI and UEFI, and sadly, there is no discernible distinction between the two (e.g., both PI and UEFI use identifiers with EFI_ type and enum identifier prefixes) 'platform init' in the context of this discussion is something completely separate, and has zero bearing on the PI<->UEFI handover in Tianocore (which is not really a handover to begin with). There is code in Tianocore which allows it to run as a 'payload', which means [presumably] that only the DXE and subsequent phases are launched from a 'platform init' component that describes the platform using some of the DT bindings that are under discussion here. In this case, I can see how some of the ACPI descriptions provided by the 'platform init' might be inherited by the 'payload'. However, I don't see how such a Tianocore payload would make meaningful use of boot/runtime code/data described in general terms using this proposed binding, which is why I keep asking for an example scenario.
