1. 根目录:
2. arch
3. hexagon
4. include
5. asm
6. system.h

/*
 * System level definitions for the Hexagon architecture
 *
 * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#ifndef _ASM_SYSTEM_H
#define _ASM_SYSTEM_H

#include <linux/linkage.h>
#include <linux/irqflags.h>
#include <asm/atomic.h>
#include <asm/hexagon_vm.h>

struct thread_struct;

extern struct task_struct *__switch_to(struct task_struct *,
	struct task_struct *,
	struct task_struct *);

#define switch_to(p, n, r) do {\
	r = __switch_to((p), (n), (r));\
} while (0)


#define rmb()				barrier()
#define read_barrier_depends()		barrier()
#define wmb()				barrier()
#define mb()				barrier()
#define smp_rmb()			barrier()
#define smp_read_barrier_depends()	barrier()
#define smp_wmb()			barrier()
#define smp_mb()			barrier()
#define smp_mb__before_atomic_dec()	barrier()
#define smp_mb__after_atomic_dec()	barrier()
#define smp_mb__before_atomic_inc()	barrier()
#define smp_mb__after_atomic_inc()	barrier()

/*
 * __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 xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
	sizeof(*(ptr))))

/*  Set a value and use a memory barrier.  Used by the scheduler somewhere.  */
#define set_mb(var, value) \
	do { var = value; mb(); } while (0)

/*
 *  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 __HAVE_ARCH_CMPXCHG 1

#define 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;						\
})

/*  Should probably shoot for an 8-byte aligned stack pointer  */
#define STACK_MASK (~7)
#define arch_align_stack(x) (x & STACK_MASK)

#endif