MIPS: Remove open-coded cmpxchg() in set_pte()

set_pte() contains an open coded version of cmpxchg() - it atomically
replaces the buddy pte's value if it is currently zero. Simplify the
code considerably by just using cmpxchg() instead of reinventing it.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org

arch/mips/include/asm/pgtable.h

@@ -17,6 +17,7 @@
 #include <asm/pgtable-64.h>
 #endif
 
+#include <asm/cmpxchg.h>
 #include <asm/io.h>
 #include <asm/pgtable-bits.h>
 
@@ -204,49 +205,7 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
 		 * Make sure the buddy is global too (if it's !none,
 		 * it better already be global)
 		 */
-#ifdef CONFIG_SMP
-		/*
-		 * For SMP, multiple CPUs can race, so we need to do
-		 * this atomically.
-		 */
-		unsigned long page_global = _PAGE_GLOBAL;
-		unsigned long tmp;
-
-		if (kernel_uses_llsc && R10000_LLSC_WAR) {
-			__asm__ __volatile__ (
-			"	.set	push				\n"
-			"	.set	arch=r4000			\n"
-			"	.set	noreorder			\n"
-			"1:"	__LL	"%[tmp], %[buddy]		\n"
-			"	bnez	%[tmp], 2f			\n"
-			"	 or	%[tmp], %[tmp], %[global]	\n"
-				__SC	"%[tmp], %[buddy]		\n"
-			"	beqzl	%[tmp], 1b			\n"
-			"	nop					\n"
-			"2:						\n"
-			"	.set	pop				\n"
-			: [buddy] "+m" (buddy->pte), [tmp] "=&r" (tmp)
-			: [global] "r" (page_global));
-		} else if (kernel_uses_llsc) {
-			__asm__ __volatile__ (
-			"	.set	push				\n"
-			"	.set	"MIPS_ISA_ARCH_LEVEL"		\n"
-			"	.set	noreorder			\n"
-			"1:"	__LL	"%[tmp], %[buddy]		\n"
-			"	bnez	%[tmp], 2f			\n"
-			"	 or	%[tmp], %[tmp], %[global]	\n"
-				__SC	"%[tmp], %[buddy]		\n"
-			"	beqz	%[tmp], 1b			\n"
-			"	nop					\n"
-			"2:						\n"
-			"	.set	pop				\n"
-			: [buddy] "+m" (buddy->pte), [tmp] "=&r" (tmp)
-			: [global] "r" (page_global));
-		}
-#else /* !CONFIG_SMP */
-		if (pte_none(*buddy))
-			pte_val(*buddy) = pte_val(*buddy) | _PAGE_GLOBAL;
-#endif /* CONFIG_SMP */
+		cmpxchg(&buddy->pte, 0, _PAGE_GLOBAL);
 	}
 #endif
 }