process.c

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/*
 *  Port on Texas Instruments TMS320C6x architecture
 *
 *  Copyright (C) 2004, 2006, 2009, 2010, 2011 Texas Instruments Incorporated
 *  Author: Aurelien Jacquiot ([email protected])
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 */
#include <linux/module.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/init_task.h>
#include <linux/tick.h>
#include <linux/mqueue.h>
#include <linux/syscalls.h>
#include <linux/reboot.h>

#include <asm/syscalls.h>

/* hooks for board specific support */
void    (*c6x_restart)(void);
void    (*c6x_halt)(void);

extern asmlinkage void ret_from_fork(void);
extern asmlinkage void ret_from_kernel_thread(void);

/*
 * power off function, if any
 */
void (*pm_power_off)(void);
EXPORT_SYMBOL(pm_power_off);

static void c6x_idle(void)
{
    unsigned long tmp;

    /*
     * Put local_irq_enable and idle in same execute packet
     * to make them atomic and avoid race to idle with
     * interrupts enabled.
     */
    asm volatile ("   mvc .s2 CSR,%0\n"
              "   or  .d2 1,%0,%0\n"
              "   mvc .s2 %0,CSR\n"
              "|| idle\n"
              : "=b"(tmp));
}

/*
 * The idle loop for C64x
 */
void cpu_idle(void)
{
    /* endless idle loop with no priority at all */
    while (1) {
        tick_nohz_idle_enter();
        rcu_idle_enter();
        while (1) {
            local_irq_disable();
            if (need_resched()) {
                local_irq_enable();
                break;
            }
            c6x_idle(); /* enables local irqs */
        }
        rcu_idle_exit();
        tick_nohz_idle_exit();

        preempt_enable_no_resched();
        schedule();
        preempt_disable();
    }
}

static void halt_loop(void)
{
    printk(KERN_EMERG "System Halted, OK to turn off power\n");
    local_irq_disable();
    while (1)
        asm volatile("idle\n");
}

void machine_restart(char *__unused)
{
    if (c6x_restart)
        c6x_restart();
    halt_loop();
}

void machine_halt(void)
{
    if (c6x_halt)
        c6x_halt();
    halt_loop();
}

void machine_power_off(void)
{
    if (pm_power_off)
        pm_power_off();
    halt_loop();
}

void flush_thread(void)
{
}

void exit_thread(void)
{
}

SYSCALL_DEFINE1(c6x_clone, struct pt_regs *, regs)
{
    unsigned long clone_flags;
    unsigned long newsp;

    /* syscall puts clone_flags in A4 and usp in B4 */
    clone_flags = regs->orig_a4;
    if (regs->b4)
        newsp = regs->b4;
    else
        newsp = regs->sp;

    return do_fork(clone_flags, newsp, regs, 0, (int __user *)regs->a6,
               (int __user *)regs->b6);
}

/*
 * Do necessary setup to start up a newly executed thread.
 */
void start_thread(struct pt_regs *regs, unsigned int pc, unsigned long usp)
{
    /*
     * The binfmt loader will setup a "full" stack, but the C6X
     * operates an "empty" stack. So we adjust the usp so that
     * argc doesn't get destroyed if an interrupt is taken before
     * it is read from the stack.
     *
     * NB: Library startup code needs to match this.
     */
    usp -= 8;

    set_fs(USER_DS);
    regs->pc  = pc;
    regs->sp  = usp;
    regs->tsr |= 0x40; /* set user mode */
    current->thread.usp = usp;
}

/*
 * Copy a new thread context in its stack.
 */
int copy_thread(unsigned long clone_flags, unsigned long usp,
        unsigned long ustk_size,
        struct task_struct *p, struct pt_regs *regs)
{
    struct pt_regs *childregs;

    childregs = task_pt_regs(p);

    if (!regs) {
        /* case of  __kernel_thread: we return to supervisor space */
        memset(childregs, 0, sizeof(struct pt_regs));
        childregs->sp = (unsigned long)(childregs + 1);
        p->thread.pc = (unsigned long) ret_from_kernel_thread;
        childregs->a0 = usp;        /* function */
        childregs->a1 = ustk_size;  /* argument */
    } else {
        /* Otherwise use the given stack */
        *childregs = *regs;
        childregs->sp = usp;
        p->thread.pc = (unsigned long) ret_from_fork;
    }

    /* Set usp/ksp */
    p->thread.usp = childregs->sp;
    thread_saved_ksp(p) = (unsigned long)childregs - 8;
    p->thread.wchan = p->thread.pc;
#ifdef __DSBT__
    {
        unsigned long dp;

        asm volatile ("mv .S2 b14,%0\n" : "=b"(dp));

        thread_saved_dp(p) = dp;
        if (usp == -1)
            childregs->dp = dp;
    }
#endif
    return 0;
}

unsigned long get_wchan(struct task_struct *p)
{
    return p->thread.wchan;
}