ARM: 6379/1: Assume new page cache pages have dirty D-cache

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().

The patch also sets the PG_arch_1 bit in the DMA cache maintenance
function to avoid additional cache flushing in update_mmu_cache().

Tested-by: Rabin Vincent <rabin.vincent@stericsson.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 4bc43e535d3b..e4dd0646e859 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -523,6 +523,12 @@ void ___dma_page_dev_to_cpu(struct page *page, unsigned long off,
                 outer_inv_range(paddr, paddr + size);
 
         dma_cache_maint_page(page, off, size, dir, dmac_unmap_area);
+
+        /*
+         * Mark the D-cache clean for this page to avoid extra flushing.
+         */
+        if (dir != DMA_TO_DEVICE && off == 0 && size >= PAGE_SIZE)
+                set_bit(PG_dcache_clean, &page->flags);
 }
 EXPORT_SYMBOL(___dma_page_dev_to_cpu);