sh: GUSA atomic rollback support.

This implements kernel-level atomic rollback built on top of gUSA,
as an alternative non-IRQ based atomicity method. This is generally
a faster method for platforms that are lacking the LL/SC pairs that
SH-4A and later use, and is only supportable on legacy cores.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/include/asm-sh/cmpxchg-grb.h b/include/asm-sh/cmpxchg-grb.h
new file mode 100644
index 00000000000..e2681abe764
--- /dev/null
+++ b/include/asm-sh/cmpxchg-grb.h
@@ -0,0 +1,70 @@
+#ifndef __ASM_SH_CMPXCHG_GRB_H
+#define __ASM_SH_CMPXCHG_GRB_H
+
+static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val)
+{
+        unsigned long retval;
+
+        __asm__ __volatile__ (
+                "   .align 2              \n\t"
+                "   mova    1f,   r0      \n\t" /* r0 = end point */
+                "   nop                   \n\t"
+                "   mov    r15,   r1      \n\t" /* r1 = saved sp */
+                "   mov    #-4,   r15     \n\t" /* LOGIN */
+                "   mov.l  @%1,   %0      \n\t" /* load  old value */
+                "   mov.l   %2,   @%1     \n\t" /* store new value */
+                "1: mov     r1,   r15     \n\t" /* LOGOUT */
+                : "=&r" (retval),
+                  "+r"  (m)
+                : "r"   (val)
+                : "memory", "r0", "r1");
+
+        return retval;
+}
+
+static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
+{
+        unsigned long retval;
+
+        __asm__ __volatile__ (
+                "   .align  2             \n\t"
+                "   mova    1f,   r0      \n\t" /* r0 = end point */
+                "   mov    r15,   r1      \n\t" /* r1 = saved sp */
+                "   mov    #-6,   r15     \n\t" /* LOGIN */
+                "   mov.b  @%1,   %0      \n\t" /* load  old value */
+                "   extu.b  %0,   %0      \n\t" /* extend as unsigned */
+                "   mov.b   %2,   @%1     \n\t" /* store new value */
+                "1: mov     r1,   r15     \n\t" /* LOGOUT */
+                : "=&r" (retval),
+                  "+r"  (m)
+                : "r"   (val)
+                : "memory" , "r0", "r1");
+
+        return retval;
+}
+
+static inline unsigned long __cmpxchg_u32(volatile int *m, unsigned long old,
+                                          unsigned long new)
+{
+        unsigned long retval;
+
+        __asm__ __volatile__ (
+                "   .align  2             \n\t"
+                "   mova    1f,   r0      \n\t" /* r0 = end point */
+                "   nop                   \n\t"
+                "   mov    r15,   r1      \n\t" /* r1 = saved sp */
+                "   mov    #-8,   r15     \n\t" /* LOGIN */
+                "   mov.l  @%1,   %0      \n\t" /* load  old value */
+                "   cmp/eq  %0,   %2      \n\t"
+                "   bf            1f      \n\t" /* if not equal */
+                "   mov.l   %2,   @%1     \n\t" /* store new value */
+                "1: mov     r1,   r15     \n\t" /* LOGOUT */
+                : "=&r" (retval),
+                  "+r"  (m)
+                : "r"   (new)
+                : "memory" , "r0", "r1", "t");
+
+        return retval;
+}
+
+#endif /* __ASM_SH_CMPXCHG_GRB_H */