1 files changed, 75 insertions, 0 deletions
diff --git a/arch/hexagon/include/asm/cmpxchg.h b/arch/hexagon/include/asm/cmpxchg.h
new file mode 100644
index 000000000..cdb705e14
--- /dev/null
+++ b/arch/hexagon/include/asm/cmpxchg.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * xchg/cmpxchg operations for the Hexagon architecture
+ *
+ * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
+ */
+
+#ifndef _ASM_CMPXCHG_H
+#define _ASM_CMPXCHG_H
+
+/*
+ * __xchg - atomically exchange a register and a memory location
+ * @x: value to swap
+ * @ptr: pointer to memory
+ * @size:  size of the value
+ *
+ * Only 4 bytes supported currently.
+ *
+ * Note:  there was an errata for V2 about .new's and memw_locked.
+ *
+ */
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
+				   int size)
+{
+	unsigned long retval;
+
+	/*  Can't seem to use printk or panic here, so just stop  */
+	if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
+
+	__asm__ __volatile__ (
+	"1:	%0 = memw_locked(%1);\n"    /*  load into retval */
+	"	memw_locked(%1,P0) = %2;\n" /*  store into memory */
+	"	if (!P0) jump 1b;\n"
+	: "=&r" (retval)
+	: "r" (ptr), "r" (x)
+	: "memory", "p0"
+	);
+	return retval;
+}
+
+/*
+ * Atomically swap the contents of a register with memory.  Should be atomic
+ * between multiple CPU's and within interrupts on the same CPU.
+ */
+#define arch_xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
+	sizeof(*(ptr))))
+
+/*
+ *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
+ *  looks just like atomic_cmpxchg on our arch currently with a bunch of
+ *  variable casting.
+ */
+
+#define arch_cmpxchg(ptr, old, new)				\
+({								\
+	__typeof__(ptr) __ptr = (ptr);				\
+	__typeof__(*(ptr)) __old = (old);			\
+	__typeof__(*(ptr)) __new = (new);			\
+	__typeof__(*(ptr)) __oldval = 0;			\
+								\
+	asm volatile(						\
+		"1:	%0 = memw_locked(%1);\n"		\
+		"	{ P0 = cmp.eq(%0,%2);\n"		\
+		"	  if (!P0.new) jump:nt 2f; }\n"		\
+		"	memw_locked(%1,p0) = %3;\n"		\
+		"	if (!P0) jump 1b;\n"			\
+		"2:\n"						\
+		: "=&r" (__oldval)				\
+		: "r" (__ptr), "r" (__old), "r" (__new)		\
+		: "memory", "p0"				\
+	);							\
+	__oldval;						\
+})
+
+#endif /* _ASM_CMPXCHG_H */