linux-kernel - [PATCH 4/7] microblaze: Add SMP implementation of xchg and cmpxchg

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Message-Id: <c841b4e94dbb6e2dedd30b6a4c1a47090b5c7d9f.1581522136.git.michal.simek@xilinx.com>
Date:   Wed, 12 Feb 2020 16:42:26 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     linux-kernel@...r.kernel.org, monstr@...str.eu,
        michal.simek@...inx.com, git@...inx.com, arnd@...db.de
Cc:     Stefan Asserhall <stefan.asserhall@...inx.com>
Subject: [PATCH 4/7] microblaze: Add SMP implementation of xchg and cmpxchg

From: Stefan Asserhall <stefan.asserhall@...inx.com>

Microblaze support only 32bit loads and stores that's why only 4 byte
operations are supported by SMP.

Signed-off-by: Stefan Asserhall <stefan.asserhall@...inx.com>
Signed-off-by: Michal Simek <michal.simek@...inx.com>
---

 arch/microblaze/include/asm/cmpxchg.h | 87 +++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/arch/microblaze/include/asm/cmpxchg.h b/arch/microblaze/include/asm/cmpxchg.h
index 3523b51aab36..0c24ac37df7f 100644
--- a/arch/microblaze/include/asm/cmpxchg.h
+++ b/arch/microblaze/include/asm/cmpxchg.h
@@ -4,6 +4,93 @@
 
 #ifndef CONFIG_SMP
 # include <asm-generic/cmpxchg.h>
+#else
+
+extern void __xchg_called_with_bad_pointer(void);
+
+static inline unsigned long __xchg_u32(volatile void *p, unsigned long val)
+{
+	unsigned long prev, temp;
+
+	__asm__ __volatile__ (
+		/* load conditional address in %3 to %0 */
+		"1:	lwx	%0, %3, r0;\n"
+		/* attempt store of new value */
+		"	swx	%4, %3, r0;\n"
+		/* checking msr carry flag */
+		"	addic	%1, r0, 0;\n"
+		/* store failed (MSR[C] set)? try again */
+		"	bnei	%1, 1b;\n"
+		/* Outputs: result value */
+		: "=&r" (prev), "=&r" (temp), "+m" (*(volatile unsigned int *)p)
+		/* Inputs: counter address */
+		: "r"   (p), "r" (val)
+		: "cc", "memory"
+	);
+
+	return prev;
+}
+
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
+								int size)
+{
+	if (size == 4)
+		return __xchg_u32(ptr, x);
+
+	__xchg_called_with_bad_pointer();
+	return x;
+}
+
+#define xchg(ptr, x) ({							\
+	((__typeof__(*(ptr)))						\
+		__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));	\
+})
+
+static inline unsigned long __cmpxchg_u32(volatile unsigned int *p,
+					  unsigned long old, unsigned long new)
+{
+	int result, tmp;
+
+	__asm__ __volatile__ (
+		/* load conditional address in %3 to %0 */
+		"1:	lwx	%0, %3, r0;\n"
+		/* compare loaded value with old value */
+		"	cmp	%2, %0, %4;\n"
+		/* not equal to old value, write old value */
+		"	bnei	%2, 2f;\n"
+		/* attempt store of new value*/
+		"	swx	%5, %3, r0;\n"
+		/* checking msr carry flag */
+		"	addic	%2, r0, 0;\n"
+		/* store failed (MSR[C] set)? try again */
+		"	bnei	%2, 1b;\n"
+		"2: "
+		/* Outputs : result value */
+		: "=&r" (result), "+m" (*p), "=&r" (tmp)
+		/* Inputs  : counter address, old, new */
+		: "r"   (p), "r" (old), "r" (new), "r" (&tmp)
+		: "cc", "memory"
+	);
+
+	return result;
+}
+
+static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
+				      unsigned long new, unsigned int size)
+{
+	if (size == 4)
+		return __cmpxchg_u32(ptr, old, new);
+
+	__xchg_called_with_bad_pointer();
+	return old;
+}
+
+#define cmpxchg(ptr, o, n) ({						\
+	((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o),	\
+			(unsigned long)(n), sizeof(*(ptr))));		\
+})
+
+
 #endif
 
 #endif /* _ASM_MICROBLAZE_CMPXCHG_H */
-- 
2.25.0