summaryrefslogtreecommitdiff
path: root/arch/xtensa/include/asm/byteorder.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/xtensa/include/asm/byteorder.h')
-rw-r--r--arch/xtensa/include/asm/byteorder.h80
1 files changed, 80 insertions, 0 deletions
diff --git a/arch/xtensa/include/asm/byteorder.h b/arch/xtensa/include/asm/byteorder.h
new file mode 100644
index 000000000000..07d10ad364d1
--- /dev/null
+++ b/arch/xtensa/include/asm/byteorder.h
@@ -0,0 +1,80 @@
+/*
+ * include/asm-xtensa/byteorder.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_BYTEORDER_H
+#define _XTENSA_BYTEORDER_H
+
+#include <asm/types.h>
+#include <linux/compiler.h>
+
+#ifdef __XTENSA_EL__
+# define __LITTLE_ENDIAN
+#elif defined(__XTENSA_EB__)
+# define __BIG_ENDIAN
+#else
+# error processor byte order undefined!
+#endif
+
+#define __SWAB_64_THRU_32__
+
+static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
+{
+ __u32 res;
+ /* instruction sequence from Xtensa ISA release 2/2000 */
+ __asm__("ssai 8 \n\t"
+ "srli %0, %1, 16 \n\t"
+ "src %0, %0, %1 \n\t"
+ "src %0, %0, %0 \n\t"
+ "src %0, %1, %0 \n"
+ : "=&a" (res)
+ : "a" (x)
+ );
+ return res;
+}
+#define __arch_swab32 __arch_swab32
+
+static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
+{
+ /* Given that 'short' values are signed (i.e., can be negative),
+ * we cannot assume that the upper 16-bits of the register are
+ * zero. We are careful to mask values after shifting.
+ */
+
+ /* There exists an anomaly between xt-gcc and xt-xcc. xt-gcc
+ * inserts an extui instruction after putting this function inline
+ * to ensure that it uses only the least-significant 16 bits of
+ * the result. xt-xcc doesn't use an extui, but assumes the
+ * __asm__ macro follows convention that the upper 16 bits of an
+ * 'unsigned short' result are still zero. This macro doesn't
+ * follow convention; indeed, it leaves garbage in the upport 16
+ * bits of the register.
+
+ * Declaring the temporary variables 'res' and 'tmp' to be 32-bit
+ * types while the return type of the function is a 16-bit type
+ * forces both compilers to insert exactly one extui instruction
+ * (or equivalent) to mask off the upper 16 bits. */
+
+ __u32 res;
+ __u32 tmp;
+
+ __asm__("extui %1, %2, 8, 8\n\t"
+ "slli %0, %2, 8 \n\t"
+ "or %0, %0, %1 \n"
+ : "=&a" (res), "=&a" (tmp)
+ : "a" (x)
+ );
+
+ return res;
+}
+#define __arch_swab16 __arch_swab16
+
+#include <linux/byteorder.h>
+
+#endif /* _XTENSA_BYTEORDER_H */