Commit af3d890b authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: provide xchg for sizes 1 and 2 



This is required for generic queued spinlocks, implement it.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent 74d69eaa

arch/xtensa/include/asm/cmpxchg.h

+32 −4
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 


#ifndef __ASSEMBLY__



#include <linux/bits.h>

#include <linux/stringify.h>



/*
@@ -138,6 +139,28 @@ static inline unsigned long xchg_u32(volatile int * m, unsigned long val) 
#define xchg(ptr,x) \

	((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))



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 only works if the compiler isn't horribly bad at optimizing.

 * gcc-2.5.8 reportedly can't handle this, but I define that one to
@@ -150,12 +173,17 @@ static __inline__ unsigned long 
__xchg(unsigned long x, volatile void * ptr, int size)

{

	switch (size) {

	case 1:

		return xchg_small(ptr, x, 1);

	case 2:

		return xchg_small(ptr, x, 2);

	case 4:

		return xchg_u32(ptr, x);

	}

	default:

		__xchg_called_with_bad_pointer();

		return x;

	}

}



#endif /* __ASSEMBLY__ */