LoongArch is a new RISC ISA, which is a bit like MIPS or RISC-V.
LoongArch includes a reduced 32-bit version (LA32R), a standard 32-bit
version (LA32S) and a 64-bit version (LA64). LoongArch use ACPI as its
boot protocol LoongArch-specific interrupt controllers (similar to APIC)
are already added in the next revision of ACPI Specification (current
revision is 6.4).

This patchset is adding basic LoongArch support in mainline kernel, we
can see a complete snapshot here:
https://github.com/loongson/linux/tree/loongarch-next

Cross-compile tool chain to build kernel:
https://github.com/loongson/build-tools/releases/download/2021.12.21/loongarch64-clfs-2022-03-03-cross-tools-gcc-glibc.tar.xz

A CLFS-based Linux distro:
https://github.com/loongson/build-tools/releases/download/2021.12.21/loongarch64-clfs-system-2022-03-03.tar.bz2

Open-source tool chain which is under review (Binutils is already upstream):
https://github.com/loongson/binutils-gdb/tree/upstream_v3.1
https://github.com/loongson/gcc/tree/loongarch_upstream_v6.3
https://github.com/loongson/glibc/tree/loongarch_2_35_dev_v2.2

Loongson and LoongArch documentations:
https://github.com/loongson/LoongArch-Documentation

LoongArch-specific interrupt controllers:
https://mantis.uefi.org/mantis/view.php?id=2203
https://mantis.uefi.org/mantis/view.php?id=2313

V1 -> V2:
1, Add documentation patches;
2, Restore copyright statements;
3, Split the big header patch;
4, Cleanup signal-related headers;
5, Cleanup incomplete 32-bit support;
6, Move the major PCI work to drivers/pci;
7, Rework Loongson64 platform support;
8, Rework lpj and __udelay()/__ndelay();
9, Rework page table layout config options;
10, Rework syscall/exception/interrupt with generic entry framework;
11, Simplify the VDSO/VSYSCALL implementation;
12, Use generic I/O access macros and functions;
13, Remove unaligned access emulation at present;
14, Keep clocksource code in arch since it is the "native clocksource";
15, Some other minor fixes and improvements.

V2 -> V3:
1, Rebased on 5.15-rc1;
2, Cleanup PCI code on V2;
3, Support multiple msi domain;
4, Support cacheable ioremap();
5, Use irq stack for interrupt handling;
6, Adjust struct ucontext and rt_sigframe;
7, Some other minor fixes and improvements.

V3 -> V4:
1, Rebased on 5.15-rc3;
2, Rework SMP support and remove legacy IPI;
3, Rework signal support and remove loongarch_abi;
4, Simplify phys_to_dma() and dma_to_phys();
5, Remove unused sys_mmap2() implementation;
6, Remove unused strncpy_user.S and strnlen_user.S; 
7, Some other minor fixes and improvements.

V4 -> V5:
1, Rebased on 5.15-rc4;
2, Fix a _PAGE_CHG_MASK bug;
3, Fix vdso_base() calculation;
4, Adjust syscall and ptrace code;
5, Use generic bitops implementation;
6, Avoid syscall restart handling in sys_rt_sigreturn();
7, Update commit messages.

V5 -> V6:
1, Rebased on 5.17-rc4;
2, Use GENERIC_IRQ_MIGRATION;
3, Improve sigcontext definition; 
4, Improve numa_default_distance(); 
5, Increse MINSIGSTKSZ and SIGSTKSZ;
6, Restruct pt_regs and user_pt_regs;
7, Fix a corner case of protection_map;
8, Fix some corner cases of system calls;
9, Separate module region and vmalloc region;
10, Rename registers to match official documents.

V6 -> V7:
1, Rebased on 5.17-rc6;
2, Refactor do_page_fault();
3, Adjust memblock initialization;
4, Use -mstrict-align to build kernel;
5, Reimplement elf_read_implies_exec() as other archs;
6, Some other minor fixes and improvements.

V7 -> V8:
1, Rebased on 5.17-rc8;
2, Remove useless abidefs.h;
3, Remove useless HAVE_ARCH_NODEDATA_EXTENSION;
4, Fix and simplify uaccess.h;
5, Fix bugs after pt_regs restruction;
6, Use generic copy_from_user_page()/copy_to_user_page();
7, Some other minor fixes and improvements.

Huacai Chen(22):
 Documentation: LoongArch: Add basic documentations.
 Documentation/zh_CN: Add basic LoongArch documentations.
 LoongArch: Add elf-related definitions.
 LoongArch: Add writecombine support for drm.
 LoongArch: Add build infrastructure.
 LoongArch: Add CPU definition headers.
 LoongArch: Add atomic/locking headers.
 LoongArch: Add other common headers.
 LoongArch: Add boot and setup routines.
 LoongArch: Add exception/interrupt handling. 
 LoongArch: Add process management.
 LoongArch: Add memory management.
 LoongArch: Add system call support.
 LoongArch: Add signal handling support.
 LoongArch: Add elf and module support.
 LoongArch: Add misc common routines.
 LoongArch: Add some library functions.
 LoongArch: Add PCI controller support.
 LoongArch: Add VDSO and VSYSCALL support.
 LoongArch: Add multi-processor (SMP) support.
 LoongArch: Add Non-Uniform Memory Access (NUMA) support.
 LoongArch: Add Loongson-3 default config file.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 Documentation/arch.rst                             |    1 +
 Documentation/loongarch/features.rst               |    3 +
 Documentation/loongarch/index.rst                  |   21 +
 Documentation/loongarch/introduction.rst           |  345 +++++
 Documentation/loongarch/irq-chip-model.rst         |  168 +++
 Documentation/translations/zh_CN/index.rst         |    1 +
 .../translations/zh_CN/loongarch/features.rst      |    8 +
 .../translations/zh_CN/loongarch/index.rst         |   26 +
 .../translations/zh_CN/loongarch/introduction.rst  |  318 ++++
 .../zh_CN/loongarch/irq-chip-model.rst             |  167 +++
 arch/loongarch/.gitignore                          |    9 +
 arch/loongarch/Kbuild                              |    3 +
 arch/loongarch/Kconfig                             |  421 ++++++
 arch/loongarch/Kconfig.debug                       |    0
 arch/loongarch/Makefile                            |  112 ++
 arch/loongarch/configs/loongson3_defconfig         |  768 ++++++++++
 arch/loongarch/include/asm/Kbuild                  |   29 +
 arch/loongarch/include/asm/acenv.h                 |   17 +
 arch/loongarch/include/asm/acpi.h                  |   38 +
 arch/loongarch/include/asm/addrspace.h             |  110 ++
 arch/loongarch/include/asm/asm-offsets.h           |    5 +
 arch/loongarch/include/asm/asm-prototypes.h        |    7 +
 arch/loongarch/include/asm/asm.h                   |  189 +++
 arch/loongarch/include/asm/asmmacro.h              |  302 ++++
 arch/loongarch/include/asm/atomic.h                |  362 +++++
 arch/loongarch/include/asm/barrier.h               |  159 ++
 arch/loongarch/include/asm/bitops.h                |   33 +
 arch/loongarch/include/asm/bitrev.h                |   34 +
 arch/loongarch/include/asm/boot_param.h            |   97 ++
 arch/loongarch/include/asm/bootinfo.h              |   32 +
 arch/loongarch/include/asm/branch.h                |   21 +
 arch/loongarch/include/asm/bug.h                   |   23 +
 arch/loongarch/include/asm/cache.h                 |   13 +
 arch/loongarch/include/asm/cacheflush.h            |  101 ++
 arch/loongarch/include/asm/cacheops.h              |   37 +
 arch/loongarch/include/asm/clocksource.h           |   12 +
 arch/loongarch/include/asm/cmpxchg.h               |  136 ++
 arch/loongarch/include/asm/compiler.h              |   15 +
 arch/loongarch/include/asm/cpu-features.h          |   69 +
 arch/loongarch/include/asm/cpu-info.h              |  136 ++
 arch/loongarch/include/asm/cpu.h                   |  127 ++
 arch/loongarch/include/asm/cpufeature.h            |   24 +
 arch/loongarch/include/asm/delay.h                 |   26 +
 arch/loongarch/include/asm/dma-direct.h            |   11 +
 arch/loongarch/include/asm/dma.h                   |   13 +
 arch/loongarch/include/asm/dmi.h                   |   24 +
 arch/loongarch/include/asm/efi.h                   |   33 +
 arch/loongarch/include/asm/elf.h                   |  301 ++++
 arch/loongarch/include/asm/entry-common.h          |   13 +
 arch/loongarch/include/asm/exec.h                  |   10 +
 arch/loongarch/include/asm/fb.h                    |   23 +
 arch/loongarch/include/asm/fixmap.h                |   13 +
 arch/loongarch/include/asm/fpregdef.h              |   55 +
 arch/loongarch/include/asm/fpu.h                   |  129 ++
 arch/loongarch/include/asm/futex.h                 |  108 ++
 arch/loongarch/include/asm/fw.h                    |   18 +
 arch/loongarch/include/asm/hardirq.h               |   26 +
 arch/loongarch/include/asm/hugetlb.h               |   79 +
 arch/loongarch/include/asm/hw_irq.h                |   17 +
 arch/loongarch/include/asm/idle.h                  |    9 +
 arch/loongarch/include/asm/io.h                    |  129 ++
 arch/loongarch/include/asm/irq.h                   |  133 ++
 arch/loongarch/include/asm/irq_regs.h              |   27 +
 arch/loongarch/include/asm/irqflags.h              |   78 +
 arch/loongarch/include/asm/kdebug.h                |   23 +
 arch/loongarch/include/asm/linkage.h               |   36 +
 arch/loongarch/include/asm/local.h                 |  138 ++
 arch/loongarch/include/asm/loongarch.h             | 1528 ++++++++++++++++++++
 arch/loongarch/include/asm/loongson.h              |  159 ++
 arch/loongarch/include/asm/mmu.h                   |   16 +
 arch/loongarch/include/asm/mmu_context.h           |  152 ++
 arch/loongarch/include/asm/mmzone.h                |   18 +
 arch/loongarch/include/asm/module.h                |   15 +
 arch/loongarch/include/asm/numa.h                  |   69 +
 arch/loongarch/include/asm/page.h                  |  123 ++
 arch/loongarch/include/asm/pci.h                   |   40 +
 arch/loongarch/include/asm/percpu.h                |  222 +++
 arch/loongarch/include/asm/perf_event.h            |   10 +
 arch/loongarch/include/asm/pgalloc.h               |  106 ++
 arch/loongarch/include/asm/pgtable-bits.h          |  139 ++
 arch/loongarch/include/asm/pgtable.h               |  619 ++++++++
 arch/loongarch/include/asm/prefetch.h              |   29 +
 arch/loongarch/include/asm/processor.h             |  208 +++
 arch/loongarch/include/asm/ptrace.h                |  150 ++
 arch/loongarch/include/asm/reboot.h                |   10 +
 arch/loongarch/include/asm/regdef.h                |   43 +
 arch/loongarch/include/asm/seccomp.h               |   20 +
 arch/loongarch/include/asm/serial.h                |   11 +
 arch/loongarch/include/asm/setup.h                 |   21 +
 arch/loongarch/include/asm/shmparam.h              |   12 +
 arch/loongarch/include/asm/smp.h                   |  124 ++
 arch/loongarch/include/asm/sparsemem.h             |   23 +
 arch/loongarch/include/asm/spinlock.h              |   12 +
 arch/loongarch/include/asm/spinlock_types.h        |   11 +
 arch/loongarch/include/asm/stackframe.h            |  219 +++
 arch/loongarch/include/asm/stacktrace.h            |   74 +
 arch/loongarch/include/asm/string.h                |   17 +
 arch/loongarch/include/asm/switch_to.h             |   37 +
 arch/loongarch/include/asm/syscall.h               |   74 +
 arch/loongarch/include/asm/thread_info.h           |  116 ++
 arch/loongarch/include/asm/time.h                  |   50 +
 arch/loongarch/include/asm/timex.h                 |   31 +
 arch/loongarch/include/asm/tlb.h                   |  216 +++
 arch/loongarch/include/asm/tlbflush.h              |   48 +
 arch/loongarch/include/asm/topology.h              |   41 +
 arch/loongarch/include/asm/types.h                 |   33 +
 arch/loongarch/include/asm/uaccess.h               |  316 ++++
 arch/loongarch/include/asm/unistd.h                |   11 +
 arch/loongarch/include/asm/vdso.h                  |   38 +
 arch/loongarch/include/asm/vdso/clocksource.h      |    8 +
 arch/loongarch/include/asm/vdso/gettimeofday.h     |   99 ++
 arch/loongarch/include/asm/vdso/processor.h        |   14 +
 arch/loongarch/include/asm/vdso/vdso.h             |   30 +
 arch/loongarch/include/asm/vdso/vsyscall.h         |   27 +
 arch/loongarch/include/asm/vermagic.h              |   19 +
 arch/loongarch/include/asm/vmalloc.h               |    4 +
 arch/loongarch/include/uapi/asm/Kbuild             |    2 +
 arch/loongarch/include/uapi/asm/abidefs.h          |   20 +
 arch/loongarch/include/uapi/asm/auxvec.h           |   17 +
 arch/loongarch/include/uapi/asm/bitfield.h         |   15 +
 arch/loongarch/include/uapi/asm/bitsperlong.h      |    9 +
 arch/loongarch/include/uapi/asm/break.h            |   23 +
 arch/loongarch/include/uapi/asm/byteorder.h        |   13 +
 arch/loongarch/include/uapi/asm/hwcap.h            |   20 +
 arch/loongarch/include/uapi/asm/ptrace.h           |   50 +
 arch/loongarch/include/uapi/asm/reg.h              |   59 +
 arch/loongarch/include/uapi/asm/sigcontext.h       |   63 +
 arch/loongarch/include/uapi/asm/signal.h           |   13 +
 arch/loongarch/include/uapi/asm/swab.h             |   52 +
 arch/loongarch/include/uapi/asm/ucontext.h         |   35 +
 arch/loongarch/include/uapi/asm/unistd.h           |    6 +
 arch/loongarch/kernel/Makefile                     |   26 +
 arch/loongarch/kernel/access-helper.h              |   13 +
 arch/loongarch/kernel/acpi.c                       |  502 +++++++
 arch/loongarch/kernel/asm-offsets.c                |  263 ++++
 arch/loongarch/kernel/cacheinfo.c                  |  122 ++
 arch/loongarch/kernel/cmdline.c                    |   31 +
 arch/loongarch/kernel/cmpxchg.c                    |  104 ++
 arch/loongarch/kernel/cpu-probe.c                  |  305 ++++
 arch/loongarch/kernel/dma.c                        |   40 +
 arch/loongarch/kernel/efi.c                        |  208 +++
 arch/loongarch/kernel/elf.c                        |   30 +
 arch/loongarch/kernel/entry.S                      |   89 ++
 arch/loongarch/kernel/env.c                        |  176 +++
 arch/loongarch/kernel/fpu.S                        |  264 ++++
 arch/loongarch/kernel/genex.S                      |   95 ++
 arch/loongarch/kernel/head.S                       |  102 ++
 arch/loongarch/kernel/idle.c                       |   16 +
 arch/loongarch/kernel/io.c                         |   94 ++
 arch/loongarch/kernel/irq.c                        |  140 ++
 arch/loongarch/kernel/mem.c                        |   83 ++
 arch/loongarch/kernel/module.c                     |  659 +++++++++
 arch/loongarch/kernel/numa.c                       |  461 ++++++
 arch/loongarch/kernel/proc.c                       |  127 ++
 arch/loongarch/kernel/process.c                    |  267 ++++
 arch/loongarch/kernel/ptrace.c                     |  432 ++++++
 arch/loongarch/kernel/reset.c                      |  102 ++
 arch/loongarch/kernel/rtc.c                        |   36 +
 arch/loongarch/kernel/setup.c                      |  499 +++++++
 arch/loongarch/kernel/signal.c                     |  569 ++++++++
 arch/loongarch/kernel/smp.c                        |  761 ++++++++++
 arch/loongarch/kernel/switch.S                     |   35 +
 arch/loongarch/kernel/syscall.c                    |   63 +
 arch/loongarch/kernel/time.c                       |  220 +++
 arch/loongarch/kernel/topology.c                   |   57 +
 arch/loongarch/kernel/traps.c                      |  755 ++++++++++
 arch/loongarch/kernel/vdso.c                       |  138 ++
 arch/loongarch/kernel/vmlinux.lds.S                |  115 ++
 arch/loongarch/lib/Makefile                        |    7 +
 arch/loongarch/lib/clear_user.S                    |   43 +
 arch/loongarch/lib/copy_user.S                     |   47 +
 arch/loongarch/lib/delay.c                         |   43 +
 arch/loongarch/lib/dump_tlb.c                      |  111 ++
 arch/loongarch/lib/memcpy.S                        |   32 +
 arch/loongarch/lib/memmove.S                       |   45 +
 arch/loongarch/lib/memset.S                        |   30 +
 arch/loongarch/mm/Makefile                         |    9 +
 arch/loongarch/mm/cache.c                          |  153 ++
 arch/loongarch/mm/extable.c                        |   22 +
 arch/loongarch/mm/fault.c                          |  261 ++++
 arch/loongarch/mm/hugetlbpage.c                    |   87 ++
 arch/loongarch/mm/init.c                           |  204 +++
 arch/loongarch/mm/ioremap.c                        |   27 +
 arch/loongarch/mm/maccess.c                        |   10 +
 arch/loongarch/mm/mmap.c                           |  125 ++
 arch/loongarch/mm/page.S                           |   84 ++
 arch/loongarch/mm/pgtable.c                        |  133 ++
 arch/loongarch/mm/tlb.c                            |  286 ++++
 arch/loongarch/mm/tlbex.S                          |  543 +++++++
 arch/loongarch/pci/Makefile                        |    7 +
 arch/loongarch/pci/acpi.c                          |  175 +++
 arch/loongarch/pci/pci.c                           |   98 ++
 arch/loongarch/vdso/Makefile                       |   96 ++
 arch/loongarch/vdso/elf.S                          |   15 +
 arch/loongarch/vdso/gen_vdso_offsets.sh            |   13 +
 arch/loongarch/vdso/sigreturn.S                    |   24 +
 arch/loongarch/vdso/vdso.S                         |   22 +
 arch/loongarch/vdso/vdso.lds.S                     |   72 +
 arch/loongarch/vdso/vgettimeofday.c                |   25 +
 drivers/gpu/drm/drm_vm.c                           |    2 +-
 drivers/gpu/drm/ttm/ttm_module.c                   |    2 +-
 include/drm/drm_cache.h                            |    8 +
 include/linux/cpuhotplug.h                         |    1 +
 include/uapi/linux/audit.h                         |    2 +
 include/uapi/linux/elf-em.h                        |    1 +
 include/uapi/linux/elf.h                           |    5 +
 include/uapi/linux/kexec.h                         |    1 +
 scripts/sorttable.c                                |    5 +
 scripts/subarch.include                            |    2 +-
 tools/include/uapi/asm/bitsperlong.h               |    2 +
 210 files changed, 22656 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/loongarch/features.rst
 create mode 100644 Documentation/loongarch/index.rst
 create mode 100644 Documentation/loongarch/introduction.rst
 create mode 100644 Documentation/loongarch/irq-chip-model.rst
 create mode 100644 Documentation/translations/zh_CN/loongarch/features.rst
 create mode 100644 Documentation/translations/zh_CN/loongarch/index.rst
 create mode 100644 Documentation/translations/zh_CN/loongarch/introduction.rst
 create mode 100644 Documentation/translations/zh_CN/loongarch/irq-chip-model.rst
 create mode 100644 arch/loongarch/.gitignore
 create mode 100644 arch/loongarch/Kbuild
 create mode 100644 arch/loongarch/Kconfig
 create mode 100644 arch/loongarch/Kconfig.debug
 create mode 100644 arch/loongarch/Makefile
 create mode 100644 arch/loongarch/configs/loongson3_defconfig
 create mode 100644 arch/loongarch/include/asm/Kbuild
 create mode 100644 arch/loongarch/include/asm/acenv.h
 create mode 100644 arch/loongarch/include/asm/acpi.h
 create mode 100644 arch/loongarch/include/asm/addrspace.h
 create mode 100644 arch/loongarch/include/asm/asm-offsets.h
 create mode 100644 arch/loongarch/include/asm/asm-prototypes.h
 create mode 100644 arch/loongarch/include/asm/asm.h
 create mode 100644 arch/loongarch/include/asm/asmmacro.h
 create mode 100644 arch/loongarch/include/asm/atomic.h
 create mode 100644 arch/loongarch/include/asm/barrier.h
 create mode 100644 arch/loongarch/include/asm/bitops.h
 create mode 100644 arch/loongarch/include/asm/bitrev.h
 create mode 100644 arch/loongarch/include/asm/boot_param.h
 create mode 100644 arch/loongarch/include/asm/bootinfo.h
 create mode 100644 arch/loongarch/include/asm/branch.h
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 create mode 100644 arch/loongarch/include/asm/clocksource.h
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 create mode 100644 arch/loongarch/include/asm/compiler.h
 create mode 100644 arch/loongarch/include/asm/cpu-features.h
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 create mode 100644 arch/loongarch/include/asm/efi.h
 create mode 100644 arch/loongarch/include/asm/elf.h
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 create mode 100644 arch/loongarch/include/asm/fpregdef.h
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 create mode 100644 arch/loongarch/include/asm/hardirq.h
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 create mode 100644 arch/loongarch/include/asm/idle.h
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 create mode 100644 arch/loongarch/include/asm/irq.h
 create mode 100644 arch/loongarch/include/asm/irq_regs.h
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 create mode 100644 arch/loongarch/include/asm/mmzone.h
 create mode 100644 arch/loongarch/include/asm/module.h
 create mode 100644 arch/loongarch/include/asm/numa.h
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 create mode 100644 arch/loongarch/include/asm/percpu.h
 create mode 100644 arch/loongarch/include/asm/perf_event.h
 create mode 100644 arch/loongarch/include/asm/pgalloc.h
 create mode 100644 arch/loongarch/include/asm/pgtable-bits.h
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 create mode 100644 arch/loongarch/include/asm/processor.h
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 create mode 100644 arch/loongarch/include/asm/reboot.h
 create mode 100644 arch/loongarch/include/asm/regdef.h
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 create mode 100644 arch/loongarch/include/asm/setup.h
 create mode 100644 arch/loongarch/include/asm/shmparam.h
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 create mode 100644 arch/loongarch/include/asm/tlbflush.h
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--
2.27.0

On Sat, Mar 19, 2022 at 3:27 PM Huacai Chen <chenhuacai@kernel.org> wrote:
>
> LoongArch is a new RISC ISA, which is a bit like MIPS or RISC-V.
> LoongArch includes a reduced 32-bit version (LA32R), a standard 32-bit
> version (LA32S) and a 64-bit version (LA64). LoongArch use ACPI as its
> boot protocol LoongArch-specific interrupt controllers (similar to APIC)
> are already added in the next revision of ACPI Specification (current
> revision is 6.4).
>
> This patchset is adding basic LoongArch support in mainline kernel, we
> can see a complete snapshot here:
> https://github.com/loongson/linux/tree/loongarch-next

This looks fine to me for the most part, and I only had comments on
a couple of things that we we had discussed before. I think the syscall
interface and the spinlock implementation bits can be addressed now
by leaving the controversial bits out of the submission, but the boot
interface still remains to be resolved.

As discussed before, I think the best way to do this is to not have a
documented custom interface but instead use the UEFI wrapper
code for both the (current) ACPI based boot and potential DT based
embedded systems that may get added later.

       Arnd

On Mon, Mar 21, 2022 at 4:09 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> This looks fine to me for the most part [...]

So it looks like this is getting there.. Do we have a way forward for
this to be merged?

I obviously can take the patches, but it would be even nicer to have a
pull request, and you'd be the obvious person since you are - whether
you like it or not - the "odd architecture guy".

Hint hint ;)

            Linus

On Mon, Mar 21, 2022 at 5:59 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Mon, Mar 21, 2022 at 4:09 AM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > This looks fine to me for the most part [...]
>
> So it looks like this is getting there.. Do we have a way forward for
> this to be merged?
>
> I obviously can take the patches, but it would be even nicer to have a
> pull request, and you'd be the obvious person since you are - whether
> you like it or not - the "odd architecture guy".

I can prepare a pull request when it gets to that, but I think the boot protocol
should be fixed first, and that makes it 5.19 material.

The TL;DR version here is that LoongArch requires the use of ACPI/UEFI
firmware, but does not currently enter the kernel using the UEFI protocol.

Instead, grub gets loaded by the firmware (not sure using which protocol),
and it then loads the kernel from disk, entering it through an ad-hoc
method passing data from grub to the kernel using a combination of
CPU registers and in-memory data structures that are different from
how UEFI passes the same information using the drivers/firmware/efi
stub entry.

We have already discussed that this will be replaced with a regular
UEFI entry using the same code that x86 and arm64 have, but at the
moment, neither the specification nor the code is there.

Merging the current version and changing it to the standard boot
protocol later would mean they'd have to keep both protocols in
the kernel, which adds complexity.

         Arnd

On Mon, Mar 21, 2022 at 2:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> I can prepare a pull request when it gets to that, but I think the boot protocol
> should be fixed first, and that makes it 5.19 material.

Thanks. No problem on 5.19, it's not like I don't have enough pending
for this merge window already..

                 Linus