ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction

this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
so that we can use some architecture's bitrev hardware instruction
to do bitrev operation.

Introduce __constant_bitrev* macro for constant bitrev operation.

Change __bitrev16() __bitrev32() to be inline function,
don't need export symbol for these tiny functions.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 84 insertions, 19 deletions

diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index 7ffe03f4693d..fb790b8449c1 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -3,14 +3,83 @@
 
 #include <linux/types.h>
 
-extern u8 const byte_rev_table[256];
+#ifdef CONFIG_HAVE_ARCH_BITREVERSE
+#include <asm/bitrev.h>
+
+#define __bitrev32 __arch_bitrev32
+#define __bitrev16 __arch_bitrev16
+#define __bitrev8 __arch_bitrev8
 
-static inline u8 bitrev8(u8 byte)
+#else
+extern u8 const byte_rev_table[256];
+static inline u8 __bitrev8(u8 byte)
 {
         return byte_rev_table[byte];
 }
 
-extern u16 bitrev16(u16 in);
-extern u32 bitrev32(u32 in);
+static inline u16 __bitrev16(u16 x)
+{
+        return (__bitrev8(x & 0xff) << 8) | __bitrev8(x >> 8);
+}
+
+static inline u32 __bitrev32(u32 x)
+{
+        return (__bitrev16(x & 0xffff) << 16) | __bitrev16(x >> 16);
+}
+
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
+
+#define __constant_bitrev32(x)  \
+({                                      \
+        u32 __x = x;                    \
+        __x = (__x >> 16) | (__x << 16);        \
+        __x = ((__x & (u32)0xFF00FF00UL) >> 8) | ((__x & (u32)0x00FF00FFUL) << 8);      \
+        __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4);      \
+        __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2);      \
+        __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1);      \
+        __x;                                                            \
+})
+
+#define __constant_bitrev16(x)  \
+({                                      \
+        u16 __x = x;                    \
+        __x = (__x >> 8) | (__x << 8);  \
+        __x = ((__x & (u16)0xF0F0U) >> 4) | ((__x & (u16)0x0F0FU) << 4);        \
+        __x = ((__x & (u16)0xCCCCU) >> 2) | ((__x & (u16)0x3333U) << 2);        \
+        __x = ((__x & (u16)0xAAAAU) >> 1) | ((__x & (u16)0x5555U) << 1);        \
+        __x;                                                            \
+})
+
+#define __constant_bitrev8(x)   \
+({                                      \
+        u8 __x = x;                     \
+        __x = (__x >> 4) | (__x << 4);  \
+        __x = ((__x & (u8)0xCCU) >> 2) | ((__x & (u8)0x33U) << 2);      \
+        __x = ((__x & (u8)0xAAU) >> 1) | ((__x & (u8)0x55U) << 1);      \
+        __x;                                                            \
+})
+
+#define bitrev32(x) \
+({                      \
+        u32 __x = x;    \
+        __builtin_constant_p(__x) ?     \
+        __constant_bitrev32(__x) :                      \
+        __bitrev32(__x);                                \
+})
+
+#define bitrev16(x) \
+({                      \
+        u16 __x = x;    \
+        __builtin_constant_p(__x) ?     \
+        __constant_bitrev16(__x) :                      \
+        __bitrev16(__x);                                \
+ })
 
+#define bitrev8(x) \
+({                      \
+        u8 __x = x;     \
+        __builtin_constant_p(__x) ?     \
+        __constant_bitrev8(__x) :                       \
+        __bitrev8(__x)  ;                       \
+ })
 #endif /* _LINUX_BITREV_H */
diff --git a/lib/Kconfig b/lib/Kconfig
index 54cf309a92a5..cd177caf3876 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -13,6 +13,15 @@ config RAID6_PQ
 config BITREVERSE
         tristate
 
+config HAVE_ARCH_BITREVERSE
+        boolean
+        default n
+        depends on BITREVERSE
+        help
+          This option provides an config for the architecture which have instruction
+          can do bitreverse operation, we use the hardware instruction if the architecture
+          have this capability.
+
 config RATIONAL
         boolean
 
diff --git a/lib/bitrev.c b/lib/bitrev.c
index 3956203456d4..40ffda94cc5d 100644
--- a/lib/bitrev.c
+++ b/lib/bitrev.c
@@ -1,3 +1,4 @@
+#ifndef CONFIG_HAVE_ARCH_BITREVERSE
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/bitrev.h>
@@ -42,18 +43,4 @@ const u8 byte_rev_table[256] = {
 };
 EXPORT_SYMBOL_GPL(byte_rev_table);
 
-u16 bitrev16(u16 x)
-{
-        return (bitrev8(x & 0xff) << 8) | bitrev8(x >> 8);
-}
-EXPORT_SYMBOL(bitrev16);
-
-/**
- * bitrev32 - reverse the order of bits in a u32 value
- * @x: value to be bit-reversed
- */
-u32 bitrev32(u32 x)
-{
-        return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);
-}
-EXPORT_SYMBOL(bitrev32);
+#endif /* CONFIG_HAVE_ARCH_BITREVERSE */