Commit 489e0f80 authored by Stafford Horne's avatar Stafford Horne
Browse files

openrisc: add 1 and 2 byte cmpxchg support 



OpenRISC only supports hardware instructions that perform 4 byte atomic
operations.  For enabling qrwlocks for upcoming SMP support 1 and 2 byte
implementations are needed.  To do this we leverage the 4 byte atomic
operations and shift/mask the 1 and 2 byte areas as needed.

This heavily borrows ideas and routines from sh and mips, which do
something similar.

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarStafford Horne <shorne@gmail.com>
parent 91993c8c

arch/openrisc/include/asm/cmpxchg.h

+115 −32
Original line number Diff line number Diff line 
/*

 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.

 *

 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>

 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>

 *

 * This file is licensed under the terms of the GNU General Public License

 * version 2.  This program is licensed "as is" without any warranty of any

 * kind, whether express or implied.

 *

 * Note:

 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4

 * byte cmpxchg is sourced heavily from the sh and mips implementations.

 */



#ifndef __ASM_OPENRISC_CMPXCHG_H

#define __ASM_OPENRISC_CMPXCHG_H



#include  <linux/types.h>



/*

 * This function doesn't exist, so you'll get a linker error

 * if something tries to do an invalid cmpxchg().

 */

extern void __cmpxchg_called_with_bad_pointer(void);

#include  <linux/bitops.h>



#define __HAVE_ARCH_CMPXCHG 1



static inline unsigned long

__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)

static inline unsigned long cmpxchg_u32(volatile void *ptr,

		unsigned long old, unsigned long new)

{

	if (size != 4) {

		__cmpxchg_called_with_bad_pointer();

		return old;

	}



	__asm__ __volatile__(

		"1:	l.lwa %0, 0(%1)		\n"

		"	l.sfeq %0, %2		\n"
@@ -43,6 +40,97 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) 
	return old;

}



static inline unsigned long xchg_u32(volatile void *ptr,

		unsigned long val)

{

	__asm__ __volatile__(

		"1:	l.lwa %0, 0(%1)		\n"

		"	l.swa 0(%1), %2		\n"

		"	l.bnf 1b		\n"

		"	 l.nop			\n"

		: "=&r"(val)

		: "r"(ptr), "r"(val)

		: "cc", "memory");



	return val;

}



static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,

				int size)

{

	int off = (unsigned long)ptr % sizeof(u32);

	volatile u32 *p = ptr - off;

#ifdef __BIG_ENDIAN

	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;

#else

	int bitoff = off * BITS_PER_BYTE;

#endif

	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;

	u32 load32, old32, new32;

	u32 ret;



	load32 = READ_ONCE(*p);



	while (true) {

		ret = (load32 & bitmask) >> bitoff;

		if (old != ret)

			return ret;



		old32 = (load32 & ~bitmask) | (old << bitoff);

		new32 = (load32 & ~bitmask) | (new << bitoff);



		/* Do 32 bit cmpxchg */

		load32 = cmpxchg_u32(p, old32, new32);

		if (load32 == old32)

			return old;

	}

}



/* xchg */



static inline u32 xchg_small(volatile void *ptr, u32 x, int size)

{

	int off = (unsigned long)ptr % sizeof(u32);

	volatile u32 *p = ptr - off;

#ifdef __BIG_ENDIAN

	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;

#else

	int bitoff = off * BITS_PER_BYTE;

#endif

	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;

	u32 oldv, newv;

	u32 ret;



	do {

		oldv = READ_ONCE(*p);

		ret = (oldv & bitmask) >> bitoff;

		newv = (oldv & ~bitmask) | (x << bitoff);

	} while (cmpxchg_u32(p, oldv, newv) != oldv);



	return ret;

}



/*

 * This function doesn't exist, so you'll get a linker error

 * if something tries to do an invalid cmpxchg().

 */

extern unsigned long __cmpxchg_called_with_bad_pointer(void)

	__compiletime_error("Bad argument size for cmpxchg");



static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,

		unsigned long new, int size)

{

	switch (size) {

	case 1:

	case 2:

		return cmpxchg_small(ptr, old, new, size);

	case 4:

		return cmpxchg_u32(ptr, old, new);

	default:

		return __cmpxchg_called_with_bad_pointer();

	}

}



#define cmpxchg(ptr, o, n)						\

	({								\

		(__typeof__(*(ptr))) __cmpxchg((ptr),			\
@@ -55,32 +143,27 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) 
 * This function doesn't exist, so you'll get a linker error if

 * something tries to do an invalidly-sized xchg().

 */

extern void __xchg_called_with_bad_pointer(void);

extern unsigned long __xchg_called_with_bad_pointer(void)

	__compiletime_error("Bad argument size for xchg");



static inline unsigned long __xchg(unsigned long val, volatile void *ptr,

static inline unsigned long __xchg(volatile void *ptr, unsigned long with,

		int size)

{

	if (size != 4) {

		__xchg_called_with_bad_pointer();

		return val;

	switch (size) {

	case 1:

	case 2:

		return xchg_small(ptr, with, size);

	case 4:

		return xchg_u32(ptr, with);

	default:

		return __xchg_called_with_bad_pointer();

	}



	__asm__ __volatile__(

		"1:	l.lwa %0, 0(%1)		\n"

		"	l.swa 0(%1), %2		\n"

		"	l.bnf 1b		\n"

		"	 l.nop			\n"

		: "=&r"(val)

		: "r"(ptr), "r"(val)

		: "cc", "memory");



	return val;

}



#define xchg(ptr, with) 						\

	({								\

		(__typeof__(*(ptr))) __xchg((unsigned long)(with),	\

					    (ptr),			\

		(__typeof__(*(ptr))) __xchg((ptr),			\

					    (unsigned long)(with),	\

					    sizeof(*(ptr)));		\

	})

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