sh: Support for SH-2A 32-bit opcodes.

SH-2A supports both 16 and 32-bit instructions, add a simple helper
for figuring out the instruction size in the places where there are
hardcoded 16-bit assumptions.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/arch/sh/kernel/cpu/sh2a/opcode_helper.c b/arch/sh/kernel/cpu/sh2a/opcode_helper.c
new file mode 100644
index 00000000000..9704b7926d8
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh2a/opcode_helper.c
@@ -0,0 +1,55 @@
+/*
+ * arch/sh/kernel/cpu/sh2a/opcode_helper.c
+ *
+ * Helper for the SH-2A 32-bit opcodes.
+ *
+ *  Copyright (C) 2007  Paul Mundt
+ *
+ * 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.
+ */
+#include <linux/kernel.h>
+#include <asm/system.h>
+
+/*
+ * Instructions on SH are generally fixed at 16-bits, however, SH-2A
+ * introduces some 32-bit instructions. Since there are no real
+ * constraints on their use (and they can be mixed and matched), we need
+ * to check the instruction encoding to work out if it's a true 32-bit
+ * instruction or not.
+ *
+ * Presently, 32-bit opcodes have only slight variations in what the
+ * actual encoding looks like in the first-half of the instruction, which
+ * makes it fairly straightforward to differentiate from the 16-bit ones.
+ *
+ * First 16-bits of encoding            Used by
+ *
+ *      0011nnnnmmmm0001        mov.b, mov.w, mov.l, fmov.d,
+ *                              fmov.s, movu.b, movu.w
+ *
+ *      0011nnnn0iii1001        bclr.b, bld.b, bset.b, bst.b, band.b,
+ *                              bandnot.b, bldnot.b, bor.b, bornot.b,
+ *                              bxor.b
+ *
+ *      0000nnnniiii0000        movi20
+ *      0000nnnniiii0001        movi20s
+ */
+unsigned int instruction_size(unsigned int insn)
+{
+        /* Look for the common cases */
+        switch ((insn & 0xf00f)) {
+        case 0x0000:    /* movi20 */
+        case 0x0001:    /* movi20s */
+        case 0x3001:    /* 32-bit mov/fmov/movu variants */
+                return 4;
+        }
+
+        /* And the special cases.. */
+        switch ((insn & 0xf08f)) {
+        case 0x3009:    /* 32-bit b*.b bit operations */
+                return 4;
+        }
+
+        return 2;
+}