MIPS: Octeon: Adjust top of DMA32 zone.

On OCTEON, we reserve the last 256MB of 32-bit PCI address space, mapping
the RAM in this region at a high DMA address.  This makes memory in this
region unavailable for 32-bit DMA.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Patchwork: http://patchwork.linux-mips.org/patch/1634/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mach-cavium-octeon/cpu-feature-overrides.h

@@ -81,4 +81,10 @@ static inline int octeon_has_saa(void)
 	return id >= 0x000d0300;
 }
 
+/*
+ * The last 256MB are reserved for device to device mappings and the
+ * BAR1 hole.
+ */
+#define MAX_DMA32_PFN (((1ULL << 32) - (1ULL << 28)) >> PAGE_SHIFT)
+
 #endif