[ARM] 3439/2: xsc3: add I/O coherency support

Patch from Lennert Buytenhek

This patch adds support for the I/O coherent cache available on the
xsc3.  The approach is to provide a simple API to determine whether the
chipset supports coherency by calling arch_is_coherent() and then
setting the appropriate system memory PTE and PMD bits.  In addition,
we call this API on dma_alloc_coherent() and dma_map_single() calls.
A generic version exists that will compile out all the coherency-related
code that is not needed on the majority of ARM systems.

Note that we do not check for coherency in the dma_alloc_writecombine()
function as that still requires a special PTE setting.  We also don't
touch dma_mmap_coherent() as that is a special ARM-only API that is by
definition only used on non-coherent system.

Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/asm-arm/pgtable-hwdef.h b/include/asm-arm/pgtable-hwdef.h
index 1d033495cc75..1bc1f997bda2 100644
--- a/include/asm-arm/pgtable-hwdef.h
+++ b/include/asm-arm/pgtable-hwdef.h
@@ -73,6 +73,7 @@
 #define PTE_EXT_AP_URW_SRW      (PTE_EXT_AP1|PTE_EXT_AP0)
 #define PTE_EXT_TEX(x)          ((x) << 6)      /* v5 */
 #define PTE_EXT_APX             (1 << 9)        /* v6 */
+#define PTE_EXT_COHERENT        (1 << 9)        /* XScale3 */
 #define PTE_EXT_SHARED          (1 << 10)       /* v6 */
 #define PTE_EXT_NG              (1 << 11)       /* v6 */