LoongArch: Remove superfluous flush_dcache_page() definition

LoongArch doesn't have cache aliases, so flush_dcache_page() is a no-op.
There is a generic implementation for this case in include/asm-generic/
cacheflush.h. So remove the superfluous flush_dcache_page() definition,
which also silences such build warnings:

In file included from crypto/scompress.c:12:
include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone':
include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable]
76 | struct page *page;
| ^~~~
crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
>> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable]
174 | struct page *dst_page = sg_page(req->dst);
|

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@intel.com/
Suggested-by: Barry Song <baohua@kernel.org>
Acked-by: Barry Song <baohua@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

mm: rationalise flush_icache_pages() and flush_icache_page()

Move the default (no-op) implementation of flush_icache_pages() to
<linux/cacheflush.h> from <asm-generic/cacheflush.h>. Remove the
flush_icache_page() wrapper from each architecture into
<linux/cacheflush.h>.

Link: https://lkml.kernel.org/r/20230802151406.3735276-32-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

loongarch: implement the new page table range API

Add update_mmu_cache_range() and change _PFN_SHIFT to PFN_PTE_SHIFT. It
would probably be more efficient to implement __update_tlb() by flushing
the entire folio instead of calling __update_tlb() N times, but I'll leave
that for someone who understands the architecture better.

Link: https://lkml.kernel.org/r/20230802151406.3735276-15-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

LoongArch: Refactor cache probe and flush methods

Current cache probe and flush methods have some drawbacks:
1, Assume there are 3 cache levels and only 3 levels;
2, Assume L1 = I + D, L2 = V, L3 = S, V is exclusive, S is inclusive.

However, the fact is I + D, I + D + V, I + D + S and I + D + V + S are
all valid. So, refactor the cache probe and flush methods to adapt more
types of cache hierarchy.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add memory management

Add memory management support for LoongArch, including: cache and tlb
management, page fault handling and ioremap/mmap support.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>