powerpc/mm: Refactor pte_update() on book3s/32

When CONFIG_PTE_64BIT is set, pte_update() operates on
'unsigned long long'
When CONFIG_PTE_64BIT is not set, pte_update() operates on
'unsigned long'

In asm/page.h, we have pte_basic_t which is 'unsigned long long'
when CONFIG_PTE_64BIT is set and 'unsigned long' otherwise.

Refactor pte_update() using pte_basic_t.

While we are at it, drop the comment on 44x which is not applicable
to book3s version of pte_update().
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c78912bc8613fb249c3d80aeb1062796b5c49400.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/book3s/32/pgtable.h

@@ -253,53 +253,35 @@ extern void flush_hash_entry(struct mm_struct *mm, pte_t *ptep,
  * and the PTE may be either 32 or 64 bit wide. In the later case,
  * when using atomic updates, only the low part of the PTE is
  * accessed atomically.
- *
- * In addition, on 44x, we also maintain a global flag indicating
- * that an executable user mapping was modified, which is needed
- * to properly flush the virtually tagged instruction cache of
- * those implementations.
  */
-#ifndef CONFIG_PTE_64BIT
-static inline unsigned long pte_update(pte_t *p,
-				       unsigned long clr,
-				       unsigned long set)
+static inline pte_basic_t pte_update(pte_t *p, unsigned long clr, unsigned long set)
 {
-	unsigned long old, tmp;
-
-	__asm__ __volatile__("\
-1:	lwarx	%0,0,%3\n\
-	andc	%1,%0,%4\n\
-	or	%1,%1,%5\n"
-"	stwcx.	%1,0,%3\n\
-	bne-	1b"
-	: "=&r" (old), "=&r" (tmp), "=m" (*p)
-	: "r" (p), "r" (clr), "r" (set), "m" (*p)
-	: "cc" );
-
-	return old;
-}
-#else /* CONFIG_PTE_64BIT */
-static inline unsigned long long pte_update(pte_t *p,
-					    unsigned long clr,
-					    unsigned long set)
-{
-	unsigned long long old;
+	pte_basic_t old;
 	unsigned long tmp;
 
-	__asm__ __volatile__("\
-1:	lwarx	%L0,0,%4\n\
-	lwzx	%0,0,%3\n\
-	andc	%1,%L0,%5\n\
-	or	%1,%1,%6\n"
-"	stwcx.	%1,0,%4\n\
-	bne-	1b"
+	__asm__ __volatile__(
+#ifndef CONFIG_PTE_64BIT
+"1:	lwarx	%0, 0, %3\n"
+"	andc	%1, %0, %4\n"
+#else
+"1:	lwarx	%L0, 0, %3\n"
+"	lwz	%0, -4(%3)\n"
+"	andc	%1, %L0, %4\n"
+#endif
+"	or	%1, %1, %5\n"
+"	stwcx.	%1, 0, %3\n"
+"	bne-	1b"
 	: "=&r" (old), "=&r" (tmp), "=m" (*p)
-	: "r" (p), "r" ((unsigned long)(p) + 4), "r" (clr), "r" (set), "m" (*p)
+#ifndef CONFIG_PTE_64BIT
+	: "r" (p),
+#else
+	: "b" ((unsigned long)(p) + 4),
+#endif
+	  "r" (clr), "r" (set), "m" (*p)
 	: "cc" );
 
 	return old;
 }
-#endif /* CONFIG_PTE_64BIT */
 
 /*
  * 2.6 calls this without flushing the TLB entry; this is wrong