Update for 11 Jan 2015:
Back in September 2014, a meeting was held at Linaro Connect where we discussed what issues remained before the arm64 ACPI core patches could be merged into the kernel, creating the TODO list below. I should have published this list sooner; I got focused on trying to resolve some of the issues instead.
We have made some progress on all of these items. But, I want to make sure we haven't missed something. Since this list was compiled by only the people in the room at Connect, it is probable we have. I, for one, do not yet claim omniscience.
So, I want to ask the ARM and ACPI communities:
-- Is this list correct?
-- Is this list complete?
Below is what we currently know about; very brief notes on status are included. The TL;DR versions of the TODO list and the current status can be found at:
https://wiki.linaro.org/LEG/Engineering/Kernel/ACPI/CoreUpstreamNotes
and I'll do my best to kept that up to date.
Thanks. Any and all feedback is greatly appreciated.
Changes since 14 Dec 2014: -- v6 of ACPI core patches posted -- Good progress in _OSI investigation, started preparing RFC for the mailing lists -- Precise definition of kernel behavior when defaulting to DT and/or using acpi=force being discussed again -- FWTS now runs and results posted after each merge of leg-kernel (includes ACPI) with Linus' tree (i.e., each -rc). -- ACPI on arm64 kernel document updated, under extensive discussion on the lists; starting coordination with SBBR content. -- Firmware Summit: planned for 26 Mar 2015, San Jose, CA, at the ARM office; mailing list (with archives) now up and running; updated agenda being prepared -- Merged items "Demonstrate the ACPI core patches work", and "Platform support patches need review" because of their similarity. -- Further discussions have occurred regarding "Why ACPI?"; Grant has a blog post explaining this better, and we will add that to kernel document -- Further discussion on the usage of _DSD has occurred, but much more is needed
TODO List for ACPI on arm64: ============================ 1. Define how Aarch64 OS identifies itself to firmware * Problem: * _OSI method is demonstrably unreliable. On x86, Linux claims to be Windows. * Proposal to use _OSC method as replacement is complicated and creates an explosion of combinations * Solution: * Draft and propose OS identification rules to ABST and ASWG for inclusion in ACPI spec. * Draft and propose recommended practice for current ACPI 5.1 spec platforms. * Status: Good progress in _OSI investigation, started preparing RFC for the mailing lists; general agreement to deprecate _OSI completely
2. Linux must choose DT booting by default when offered both ACPI and DT on arm64 * Status: DONE, but being revisited for possible algorithmic change
3. Linux UEFI/ACPI testing tools must be made available * Problem: * Hardware/Firmware vendors do not have tools to test Linux compatibility. * Common problems go undetected if not tested for. * Solution: * Port FWTS tool and LuvOS distribution to AArch64 * Make LuvOS images readily available * Require hardware vendors to actively test against old and new kernels. * Status: * LuvOS and FWTS ported to arm64; patches in mainline; additional test cases being written. * CI loop set up to run FWTS on Foundation model for each -rc merge of Linus' tree into leg-kernel. * AMD Seattle results pending updated kernel patches. * LuvOS details at https://wiki.linaro.org/LEG/Engineering/luvOS
4. Set clear expectations for those providing ACPI for use with Linux * Problem: * Hardware/Firmware vendors can and will create ACPI tables that cannot be used by Linux without some guidance * Kernel developers cannot determine whether the kernel or firmware is broken without knowing what the firmware should do * Solution: document the expectations, and iterate as needed. Enforce when we must. * Status: kernel text updated and under heavy discussion, AMD has made their guidance document available, and starting to coordinate content with SBBR; firmware summit date and location seems firm, agenda being updated.
5. Platform support patches need verification and review * Problem: the core Aarch64 patches have been reviewed and are in good shape, but there is not yet a good example of server platform support patches that use them. * Solution: post *good* patches for multiple ACPI platforms, demonstrating that both the core patches work, and that the use of the ACPI core makes sense. * Status: * ACPI core works on at least the Foundation model, Juno, APM Mustang, and AMD Seattle * FWTS results for the Foundation model have been posted * First version for AMD Seattle has been posted to the public linaro-acpi mailing list for initial review, refined versions to be posted to broader lists after a few iterations for basic cleanup
6. How does the kernel handle_DSD usage? * Problem: * _DSD defines key-value properties in the DT style. How do we ensure _DSD bindings are well defined? * How do we ensure DT and _DSD bindings remain consistent with each other? * Solution: public documentation for all bindings, and a process for defining them * Status: proposal to require patch authors to point at public binding documentation; kernel Documentation/devicetree/bindings remains the default if no other location exists; UEFI forum has set up a binding repository. Discussion continues.
7. Why is ACPI required? * Problem: * arm64 maintainers still haven't been convinced that ACPI is necessary. * Why do hardware and OS vendors say ACPI is required? * Solution: discussions between those who want ACPI and arm64 maintainers * Status: Grant has provided a blog post at http://www.secretlab.ca/archives/151. Al will roll that content into the kernel documentation, also.