xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

xtensa's flush_dcache_page() can be a no-op sometimes. There is a
generic implementation for this case in include/asm-generic/
cacheflush.h.
 #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
 static inline void flush_dcache_page(struct page *page)
 {
 }

 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
 #endif

So remove the superfluous flush_dcache_page() definition, which also
helps silence potential build warnings complaining the page variable
passed to flush_dcache_page() is not used.

   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);
         |

The issue was originally reported on LoongArch by kernel test
robot (Huacai fixed it on LoongArch), then reported by Guenter
and me on xtensa.

This patch also removes lots of redundant macros which have
been defined by asm-generic/cacheflush.h.

Cc: Huacai Chen <[email protected]>
Cc: Herbert Xu <[email protected]>
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Reported-by: Barry Song <[email protected]>
Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/
Reported-by: Guenter Roeck <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 77292bb ("crypto: scomp - remove memcpy if sg_nents is 1 and pages are lowmem")
Signed-off-by: Barry Song <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Max Filippov <[email protected]>

Author: Barry Song

arch/xtensa/include/asm/cacheflush.h

@@ -100,6 +100,10 @@ void flush_cache_range(struct vm_area_struct*, ulong, ulong);
 void flush_icache_range(unsigned long start, unsigned long end);
 void flush_cache_page(struct vm_area_struct*,
 			     unsigned long, unsigned long);
+#define flush_cache_all flush_cache_all
+#define flush_cache_range flush_cache_range
+#define flush_icache_range flush_icache_range
+#define flush_cache_page flush_cache_page
 #else
 #define flush_cache_all local_flush_cache_all
 #define flush_cache_range local_flush_cache_range
@@ -136,20 +140,7 @@ void local_flush_cache_page(struct vm_area_struct *vma,
 
 #else
 
-#define flush_cache_all()				do { } while (0)
-#define flush_cache_mm(mm)				do { } while (0)
-#define flush_cache_dup_mm(mm)				do { } while (0)
-
-#define flush_cache_vmap(start,end)			do { } while (0)
-#define flush_cache_vmap_early(start,end)		do { } while (0)
-#define flush_cache_vunmap(start,end)			do { } while (0)
-
-#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
-#define flush_dcache_page(page)				do { } while (0)
-
 #define flush_icache_range local_flush_icache_range
-#define flush_cache_page(vma, addr, pfn)		do { } while (0)
-#define flush_cache_range(vma, start, end)		do { } while (0)
 
 #endif
 
@@ -162,15 +153,14 @@ void local_flush_cache_page(struct vm_area_struct *vma,
 		__invalidate_icache_range(start,(end) - (start));	\
 	} while (0)
 
-#define flush_dcache_mmap_lock(mapping)			do { } while (0)
-#define flush_dcache_mmap_unlock(mapping)		do { } while (0)
-
 #if defined(CONFIG_MMU) && (DCACHE_WAY_SIZE > PAGE_SIZE)
 
 extern void copy_to_user_page(struct vm_area_struct*, struct page*,
 		unsigned long, void*, const void*, unsigned long);
 extern void copy_from_user_page(struct vm_area_struct*, struct page*,
 		unsigned long, void*, const void*, unsigned long);
+#define copy_to_user_page copy_to_user_page
+#define copy_from_user_page copy_from_user_page
 
 #else
 
@@ -186,4 +176,6 @@ extern void copy_from_user_page(struct vm_area_struct*, struct page*,
 
 #endif
 
+#include <asm-generic/cacheflush.h>
+
 #endif /* _XTENSA_CACHEFLUSH_H */