sh: Provide optimized unaligned loads on SH-4A.

This adds support for unaligned loads on SH-4A, using the SH-4A's
neutered movua.l instruction. As movua.l is r0-inspired, stores are
still handled through the packed struct.

Based on asm-generic/unaligned.h by Harvey Harrison.

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

2 files changed, 264 insertions, 1 deletions

diff --git a/arch/sh/include/asm/unaligned-sh4a.h b/arch/sh/include/asm/unaligned-sh4a.h
new file mode 100644
index 000000000000..d8f89770275b
--- /dev/null
+++ b/arch/sh/include/asm/unaligned-sh4a.h
@@ -0,0 +1,258 @@
+#ifndef __ASM_SH_UNALIGNED_SH4A_H
+#define __ASM_SH_UNALIGNED_SH4A_H
+
+/*
+ * SH-4A has support for unaligned 32-bit loads, and 32-bit loads only.
+ * Support for 16 and 64-bit accesses are done through shifting and
+ * masking relative to the endianness. Unaligned stores are not supported
+ * by the instruction encoding, so these continue to use the packed
+ * struct.
+ *
+ * The same note as with the movli.l/movco.l pair applies here, as long
+ * as the load is gauranteed to be inlined, nothing else will hook in to
+ * r0 and we get the return value for free.
+ *
+ * NOTE: Due to the fact we require r0 encoding, care should be taken to
+ * avoid mixing these heavily with other r0 consumers, such as the atomic
+ * ops. Failure to adhere to this can result in the compiler running out
+ * of spill registers and blowing up when building at low optimization
+ * levels. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34777.
+ */
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+static __always_inline u32 __get_unaligned_cpu32(const u8 *p)
+{
+	unsigned long unaligned;
+
+	__asm__ __volatile__ (
+		"movua.l	@%1, %0\n\t"
+		 : "=z" (unaligned)
+		 : "r" (p)
+	);
+
+	return unaligned;
+}
+
+struct __una_u16 { u16 x __attribute__((packed)); };
+struct __una_u32 { u32 x __attribute__((packed)); };
+struct __una_u64 { u64 x __attribute__((packed)); };
+
+static inline u16 __get_unaligned_cpu16(const u8 *p)
+{
+#ifdef __LITTLE_ENDIAN
+	return __get_unaligned_cpu32(p) & 0xffff;
+#else
+	return __get_unaligned_cpu32(p) >> 16;
+#endif
+}
+
+/*
+ * Even though movua.l supports auto-increment on the read side, it can
+ * only store to r0 due to instruction encoding constraints, so just let
+ * the compiler sort it out on its own.
+ */
+static inline u64 __get_unaligned_cpu64(const u8 *p)
+{
+#ifdef __LITTLE_ENDIAN
+	return (u64)__get_unaligned_cpu32(p + 4) << 32 |
+		    __get_unaligned_cpu32(p);
+#else
+	return (u64)__get_unaligned_cpu32(p) << 32 |
+		    __get_unaligned_cpu32(p + 4);
+#endif
+}
+
+static inline u16 get_unaligned_le16(const void *p)
+{
+	return le16_to_cpu(__get_unaligned_cpu16(p));
+}
+
+static inline u32 get_unaligned_le32(const void *p)
+{
+	return le32_to_cpu(__get_unaligned_cpu32(p));
+}
+
+static inline u64 get_unaligned_le64(const void *p)
+{
+	return le64_to_cpu(__get_unaligned_cpu64(p));
+}
+
+static inline u16 get_unaligned_be16(const void *p)
+{
+	return be16_to_cpu(__get_unaligned_cpu16(p));
+}
+
+static inline u32 get_unaligned_be32(const void *p)
+{
+	return be32_to_cpu(__get_unaligned_cpu32(p));
+}
+
+static inline u64 get_unaligned_be64(const void *p)
+{
+	return be64_to_cpu(__get_unaligned_cpu64(p));
+}
+
+static inline void __put_le16_noalign(u8 *p, u16 val)
+{
+	*p++ = val;
+	*p++ = val >> 8;
+}
+
+static inline void __put_le32_noalign(u8 *p, u32 val)
+{
+	__put_le16_noalign(p, val);
+	__put_le16_noalign(p + 2, val >> 16);
+}
+
+static inline void __put_le64_noalign(u8 *p, u64 val)
+{
+	__put_le32_noalign(p, val);
+	__put_le32_noalign(p + 4, val >> 32);
+}
+
+static inline void __put_be16_noalign(u8 *p, u16 val)
+{
+	*p++ = val >> 8;
+	*p++ = val;
+}
+
+static inline void __put_be32_noalign(u8 *p, u32 val)
+{
+	__put_be16_noalign(p, val >> 16);
+	__put_be16_noalign(p + 2, val);
+}
+
+static inline void __put_be64_noalign(u8 *p, u64 val)
+{
+	__put_be32_noalign(p, val >> 32);
+	__put_be32_noalign(p + 4, val);
+}
+
+static inline void put_unaligned_le16(u16 val, void *p)
+{
+#ifdef __LITTLE_ENDIAN
+	((struct __una_u16 *)p)->x = val;
+#else
+	__put_le16_noalign(p, val);
+#endif
+}
+
+static inline void put_unaligned_le32(u32 val, void *p)
+{
+#ifdef __LITTLE_ENDIAN
+	((struct __una_u32 *)p)->x = val;
+#else
+	__put_le32_noalign(p, val);
+#endif
+}
+
+static inline void put_unaligned_le64(u64 val, void *p)
+{
+#ifdef __LITTLE_ENDIAN
+	((struct __una_u64 *)p)->x = val;
+#else
+	__put_le64_noalign(p, val);
+#endif
+}
+
+static inline void put_unaligned_be16(u16 val, void *p)
+{
+#ifdef __BIG_ENDIAN
+	((struct __una_u16 *)p)->x = val;
+#else
+	__put_be16_noalign(p, val);
+#endif
+}
+
+static inline void put_unaligned_be32(u32 val, void *p)
+{
+#ifdef __BIG_ENDIAN
+	((struct __una_u32 *)p)->x = val;
+#else
+	__put_be32_noalign(p, val);
+#endif
+}
+
+static inline void put_unaligned_be64(u64 val, void *p)
+{
+#ifdef __BIG_ENDIAN
+	((struct __una_u64 *)p)->x = val;
+#else
+	__put_be64_noalign(p, val);
+#endif
+}
+
+/*
+ * Cause a link-time error if we try an unaligned access other than
+ * 1,2,4 or 8 bytes long
+ */
+extern void __bad_unaligned_access_size(void);
+
+#define __get_unaligned_le(ptr) ((__force typeof(*(ptr)))({			\
+	__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr),			\
+	__builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_le16((ptr)),	\
+	__builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_le32((ptr)),	\
+	__builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_le64((ptr)),	\
+	__bad_unaligned_access_size()))));					\
+	}))
+
+#define __get_unaligned_be(ptr) ((__force typeof(*(ptr)))({			\
+	__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr),			\
+	__builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_be16((ptr)),	\
+	__builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_be32((ptr)),	\
+	__builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_be64((ptr)),	\
+	__bad_unaligned_access_size()))));					\
+	}))
+
+#define __put_unaligned_le(val, ptr) ({					\
+	void *__gu_p = (ptr);						\
+	switch (sizeof(*(ptr))) {					\
+	case 1:								\
+		*(u8 *)__gu_p = (__force u8)(val);			\
+		break;							\
+	case 2:								\
+		put_unaligned_le16((__force u16)(val), __gu_p);		\
+		break;							\
+	case 4:								\
+		put_unaligned_le32((__force u32)(val), __gu_p);		\
+		break;							\
+	case 8:								\
+		put_unaligned_le64((__force u64)(val), __gu_p);		\
+		break;							\
+	default:							\
+		__bad_unaligned_access_size();				\
+		break;							\
+	}								\
+	(void)0; })
+
+#define __put_unaligned_be(val, ptr) ({					\
+	void *__gu_p = (ptr);						\
+	switch (sizeof(*(ptr))) {					\
+	case 1:								\
+		*(u8 *)__gu_p = (__force u8)(val);			\
+		break;							\
+	case 2:								\
+		put_unaligned_be16((__force u16)(val), __gu_p);		\
+		break;							\
+	case 4:								\
+		put_unaligned_be32((__force u32)(val), __gu_p);		\
+		break;							\
+	case 8:								\
+		put_unaligned_be64((__force u64)(val), __gu_p);		\
+		break;							\
+	default:							\
+		__bad_unaligned_access_size();				\
+		break;							\
+	}								\
+	(void)0; })
+
+#ifdef __LITTLE_ENDIAN
+# define get_unaligned __get_unaligned_le
+# define put_unaligned __put_unaligned_le
+#else
+# define get_unaligned __get_unaligned_be
+# define put_unaligned __put_unaligned_be
+#endif
+
+#endif /* __ASM_SH_UNALIGNED_SH4A_H */
diff --git a/arch/sh/include/asm/unaligned.h b/arch/sh/include/asm/unaligned.h
index c1641a01d50f..8c0ad5e4487a 100644
--- a/arch/sh/include/asm/unaligned.h
+++ b/arch/sh/include/asm/unaligned.h
@@ -1,7 +1,11 @@
 #ifndef _ASM_SH_UNALIGNED_H
 #define _ASM_SH_UNALIGNED_H
 
-/* SH can't handle unaligned accesses. */
+#ifdef CONFIG_CPU_SH4A
+/* SH-4A can handle unaligned loads in a relatively neutered fashion. */
+#include <asm/unaligned-sh4a.h>
+#else
+/* Otherwise, SH can't handle unaligned accesses. */
 #ifdef __LITTLE_ENDIAN__
 # include <linux/unaligned/le_struct.h>
 # include <linux/unaligned/be_byteshift.h>
@@ -15,5 +19,6 @@
 # define get_unaligned	__get_unaligned_be
 # define put_unaligned	__put_unaligned_be
 #endif
+#endif
 
 #endif /* _ASM_SH_UNALIGNED_H */