[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.h b/include/asm-arm/pgtable.h
index e595ae24efe2..e85c08d78dda 100644
--- a/include/asm-arm/pgtable.h
+++ b/include/asm-arm/pgtable.h
@@ -156,6 +156,7 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
 #define L_PTE_WRITE             (1 << 5)
 #define L_PTE_EXEC              (1 << 6)
 #define L_PTE_DIRTY             (1 << 7)
+#define L_PTE_COHERENT          (1 << 9)        /* I/O coherent (xsc3) */
 #define L_PTE_SHARED            (1 << 10)       /* shared between CPUs (v6) */
 #define L_PTE_ASID              (1 << 11)       /* non-global (use ASID, v6) */