ARM: 8627/1: avoid cache flushing in flush_dcache_page()

When the data cache is PIPT or VIPT non-aliasing, and cache operations
are broadcast by the hardware, we can always postpone the flush in
flush_dcache_page().  A similar change was done for ARM64 in commit
b5b6c9e9 ("arm64: Avoid cache flushing in flush_dcache_page()").
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NRabin Vincent <rabinv@axis.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/flush.c

@@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
 	if (page == ZERO_PAGE(0))
 		return;
 
+	if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
+		if (test_bit(PG_dcache_clean, &page->flags))
+			clear_bit(PG_dcache_clean, &page->flags);
+		return;
+	}
+
 	mapping = page_mapping(page);
 
 	if (!cache_ops_need_broadcast() &&