sh: Assume new page cache pages have dirty dcache lines.

This follows the ARM change c01778001a4f5ad9c62d882776235f3f31922fdd
("ARM: 6379/1: Assume new page cache pages have dirty D-cache") for the
same rationale:

    There are places in Linux where writes to newly allocated page
    cache pages happen without a subsequent call to flush_dcache_page()
    (several PIO drivers including USB HCD). This patch changes the
    meaning of PG_arch_1 to be PG_dcache_clean and always flush the
    D-cache for a newly mapped page in update_mmu_cache().

This addresses issues seen with executing binaries from MMC, in
addition to some of the other HCDs that don't explicitly do cache
management for their pipe-in buffers.

Requested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/mm/cache-sh4.c b/arch/sh/mm/cache-sh4.c
index 2cfae81..92eb986 100644
--- a/arch/sh/mm/cache-sh4.c
+++ b/arch/sh/mm/cache-sh4.c
@@ -114,7 +114,7 @@
 	struct address_space *mapping = page_mapping(page);
 
 	if (mapping && !mapping_mapped(mapping))
-		set_bit(PG_dcache_dirty, &page->flags);
+		clear_bit(PG_dcache_clean, &page->flags);
 	else
 #endif
 		flush_cache_one(CACHE_OC_ADDRESS_ARRAY |
@@ -239,7 +239,7 @@
 		 * another ASID than the current one.
 		 */
 		map_coherent = (current_cpu_data.dcache.n_aliases &&
-			!test_bit(PG_dcache_dirty, &page->flags) &&
+			test_bit(PG_dcache_clean, &page->flags) &&
 			page_mapped(page));
 		if (map_coherent)
 			vaddr = kmap_coherent(page, address);