[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, 17 insertions, 0 deletions

diff --git a/include/asm-arm/arch-ixp23xx/memory.h b/include/asm-arm/arch-ixp23xx/memory.h
index bebcf0aa0d72..6e19f46d54d1 100644
--- a/include/asm-arm/arch-ixp23xx/memory.h
+++ b/include/asm-arm/arch-ixp23xx/memory.h
@@ -28,6 +28,7 @@
  *              to an address that the kernel can use.
  */
 #ifndef __ASSEMBLY__
+#include <asm/mach-types.h>
 
 #define __virt_to_bus(v)                                                \
         ({ unsigned int ret;                                            \
@@ -40,6 +41,22 @@
         data = *((volatile int *)IXP23XX_PCI_SDRAM_BAR);                \
          __phys_to_virt((((b - (data & 0xfffffff0)) + 0x00000000))); })
 
+/*
+ * Coherency support.  Only supported on A2 CPUs or on A1
+ * systems that have the cache coherency workaround.
+ */
+static inline int __ixp23xx_arch_is_coherent(void)
+{
+        extern unsigned int processor_id;
+
+        if (((processor_id & 15) >= 2) || machine_is_roadrunner())
+                return 1;
+
+        return 0;
+}
+
+#define arch_is_coherent()      __ixp23xx_arch_is_coherent()
+
 #endif