powerpc/mm: Create a dedicated pte_update() for 8xx

pte_update() is a bit special for the 8xx. At the time
being, that's an #ifdef inside the nohash/32 pte_update().

As we are going to make it even more special in the coming
patches, create a dedicated version for pte_update() for 8xx.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a103be0099ac2360f8c44f4a1a63cc03713a1360.1589866984.git.christophe.leroy@csgroup.eu

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

@@ -221,7 +221,31 @@ static inline void pmd_clear(pmd_t *pmdp)
  * that an executable user mapping was modified, which is needed
  * to properly flush the virtually tagged instruction cache of
  * those implementations.
+ *
+ * On the 8xx, the page tables are a bit special. For 16k pages, we have
+ * 4 identical entries. For other page sizes, we have a single entry in the
+ * table.
  */
+#ifdef CONFIG_PPC_8xx
+static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, pte_t *p,
+				     unsigned long clr, unsigned long set, int huge)
+{
+	pte_basic_t *entry = &p->pte;
+	pte_basic_t old = pte_val(*p);
+	pte_basic_t new = (old & ~(pte_basic_t)clr) | set;
+	int num, i;
+
+	if (!huge)
+		num = PAGE_SIZE / SZ_4K;
+	else
+		num = 1;
+
+	for (i = 0; i < num; i++, entry++)
+		*entry = new;
+
+	return old;
+}
+#else
 static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, pte_t *p,
 				     unsigned long clr, unsigned long set, int huge)
 {
@@ -242,11 +266,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p
 	pte_basic_t old = pte_val(*p);
 	pte_basic_t new = (old & ~(pte_basic_t)clr) | set;
 
-#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES)
-	p->pte = p->pte1 = p->pte2 = p->pte3 = new;
-#else
 	*p = __pte(new);
-#endif
 #endif /* !PTE_ATOMIC_UPDATES */
 
 #ifdef CONFIG_44x
@@ -255,6 +275,7 @@ static inline pte_basic_t pte_update(struct mm_struct *mm, unsigned long addr, p
 #endif
 	return old;
 }
+#endif
 
 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 static inline int __ptep_test_and_clear_young(struct mm_struct *mm,