v4.19.13 snapshot.
diff --git a/arch/sh/include/asm/spinlock-cas.h b/arch/sh/include/asm/spinlock-cas.h
new file mode 100644
index 0000000..270ee4d
--- /dev/null
+++ b/arch/sh/include/asm/spinlock-cas.h
@@ -0,0 +1,92 @@
+/*
+ * include/asm-sh/spinlock-cas.h
+ *
+ * Copyright (C) 2015 SEI
+ *
+ * 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.
+ */
+#ifndef __ASM_SH_SPINLOCK_CAS_H
+#define __ASM_SH_SPINLOCK_CAS_H
+
+#include <asm/barrier.h>
+#include <asm/processor.h>
+
+static inline unsigned __sl_cas(volatile unsigned *p, unsigned old, unsigned new)
+{
+ __asm__ __volatile__("cas.l %1,%0,@r0"
+ : "+r"(new)
+ : "r"(old), "z"(p)
+ : "t", "memory" );
+ return new;
+}
+
+/*
+ * Your basic SMP spinlocks, allowing only a single CPU anywhere
+ */
+
+#define arch_spin_is_locked(x) ((x)->lock <= 0)
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ while (!__sl_cas(&lock->lock, 1, 0));
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ __sl_cas(&lock->lock, 0, 1);
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ return __sl_cas(&lock->lock, 1, 0);
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ *
+ * NOTE! it is quite common to have readers in interrupts but no interrupt
+ * writers. For those circumstances we can "mix" irq-safe locks - any writer
+ * needs to get a irq-safe write-lock, but readers can get non-irqsafe
+ * read-locks.
+ */
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+ unsigned old;
+ do old = rw->lock;
+ while (!old || __sl_cas(&rw->lock, old, old-1) != old);
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+ unsigned old;
+ do old = rw->lock;
+ while (__sl_cas(&rw->lock, old, old+1) != old);
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+ while (__sl_cas(&rw->lock, RW_LOCK_BIAS, 0) != RW_LOCK_BIAS);
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+ __sl_cas(&rw->lock, 0, RW_LOCK_BIAS);
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+ unsigned old;
+ do old = rw->lock;
+ while (old && __sl_cas(&rw->lock, old, old-1) != old);
+ return !!old;
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+ return __sl_cas(&rw->lock, RW_LOCK_BIAS, 0) == RW_LOCK_BIAS;
+}
+
+#endif /* __ASM_SH_SPINLOCK_CAS_H */