Merge tag 'csky-for-linus-4.20' of https://github.com/c-sky/csky-linux

Pull C-SKY architecture port from Guo Ren:
"This contains the Linux port for C-SKY(csky) based on linux-4.19
Release, which

Merge tag 'csky-for-linus-4.20' of https://github.com/c-sky/csky-linux

Pull C-SKY architecture port from Guo Ren:
"This contains the Linux port for C-SKY(csky) based on linux-4.19
Release, which has been through 10 rounds of review on mailing list.

More information:

http://en.c-sky.com

The development repo:

https://github.com/c-sky/csky-linux

ABI Documentation:

https://github.com/c-sky/csky-doc

Here is the pre-built cross compiler for fast test from our CI:

https://gitlab.com/c-sky/buildroot/-/jobs/101608095/artifacts/file/output/images/csky_toolchain_qemu_csky_ck807f_4.18_glibc_defconfig_482b221e52908be1c9b2ccb444255e1562bb7025.tar.xz

We use buildroot as our CI-test enviornment. "LTP, Lmbench ..." will
be tested for every commit. See here for more details:

https://gitlab.com/c-sky/buildroot/pipelines

We'll continouslly improve csky subsystem in future"

Arnd acks, and adds the following notes:
"I did a thorough review of the ABI, which as usual mainly consists of
spotting any files that don't use the asm-generic ABI itself, and
having it changed to it matches exactly what we do on other new
architectures.

I also looked at every other patch and commented on maybe half of them
where I saw something that did not quite seem right. Others have
reviewed specific patches in greater depth. I'm sure that one could
fine more of the minor details, but as long as they are not ABI
relevant, they can be fixed later.

The only patch that is part of the ABI and that nobody reviewed is the
signal handling. This is one of the areas I never worked on in much
detail. I did not see anything wrong with it, but I also don't know
what the problems with the other architectures are here, and we seem
to be hitting issues occasionally, and we never managed to generalize
this enough for new architectures to have a trivial implementation.

I was originally hoping that we could have the 64-bit time_t
interfaces ready in time to completely drop the 32-bit ones, but that
did not happen. We might still remove them in the next merge window
depending on whether the libc upstream people prefer to keep them or
not.

One more general comment: I think this may well be the last new CPU
architecture we ever add to the kernel. Both nds32 and c-sky are made
by companies that also work on risc-v, and generally speaking risc-v
seems to be killing off any of the minor licensable instruction set
projects, just like ARM has mostly killed off the custom
vendor-specific instruction sets already.

If we add another architecture in the future, it may instead be
something like the LLVM bitcode or WebAssembly, who knows?"

To which Geert Uytterhoeven pipes in about another architecture still in
the pipeline: Kalray MPPA.

* tag 'csky-for-linus-4.20' of https://github.com/c-sky/csky-linux: (24 commits)
dt-bindings: interrupt-controller: C-SKY APB intc
irqchip: add C-SKY APB bus interrupt controller
dt-bindings: interrupt-controller: C-SKY SMP intc
irqchip: add C-SKY SMP interrupt controller
MAINTAINERS: Add csky
dt-bindings: Add vendor prefix for csky
dt-bindings: csky CPU Bindings
csky: Misc headers
csky: SMP support
csky: Debug and Ptrace GDB
csky: User access
csky: Library functions
csky: ELF and module probe
csky: Atomic operations
csky: IRQ handling
csky: VDSO and rt_sigreturn
csky: Process management and Signal
csky: MMU and page table management
csky: Cache and TLB routines
csky: System Call
...

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csky: MMU and page table management

This patch adds files related to memory management and here is our
memory-layout:

Fixmap : 0xffc02000 – 0xfffff000 (4 MB - 12KB)
Pkmap :

csky: MMU and page table management

This patch adds files related to memory management and here is our
memory-layout:

Fixmap : 0xffc02000 – 0xfffff000 (4 MB - 12KB)
Pkmap : 0xff800000 – 0xffc00000 (4 MB)
Vmalloc : 0xf0200000 – 0xff000000 (238 MB)
Lowmem : 0x80000000 – 0xc0000000 (1GB)

abiv1 CPU (CK610) is VIPT cache and it doesn't support highmem.
abiv2 CPUs are all PIPT cache and they could support highmem.

Lowmem is directly mapped by msa0 & msa1 reg, and we needn't setup
memory page table for it.

Link:https://lore.kernel.org/lkml/20180518215548.GH17671@n2100.armlinux.org.uk/
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

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