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-rw-r--r--include/asm-arm/domain.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/asm-arm/domain.h b/include/asm-arm/domain.h
index da1d960387d9..f8ea2de4848e 100644
--- a/include/asm-arm/domain.h
+++ b/include/asm-arm/domain.h
@@ -16,11 +16,29 @@
* DOMAIN_IO - domain 2 includes all IO only
* DOMAIN_USER - domain 1 includes all user memory only
* DOMAIN_KERNEL - domain 0 includes all kernel memory only
+ *
+ * The domain numbering depends on whether we support 36 physical
+ * address for I/O or not. Addresses above the 32 bit boundary can
+ * only be mapped using supersections and supersections can only
+ * be set for domain 0. We could just default to DOMAIN_IO as zero,
+ * but there may be systems with supersection support and no 36-bit
+ * addressing. In such cases, we want to map system memory with
+ * supersections to reduce TLB misses and footprint.
+ *
+ * 36-bit addressing and supersections are only available on
+ * CPUs based on ARMv6+ or the Intel XSC3 core.
*/
+#ifndef CONFIG_IO_36
#define DOMAIN_KERNEL 0
#define DOMAIN_TABLE 0
#define DOMAIN_USER 1
#define DOMAIN_IO 2
+#else
+#define DOMAIN_KERNEL 2
+#define DOMAIN_TABLE 2
+#define DOMAIN_USER 1
+#define DOMAIN_IO 0
+#endif
/*
* Domain types