arch/c6x/kernel/process.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Port on Texas Instruments TMS320C6x architecture
 *
 *  Copyright (C) 2004, 2006, 2009, 2010, 2011 Texas Instruments Incorporated
 *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
 */
#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 <linux/sched/task.h>
#include <linux/sched/task_stack.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);

void arch_cpu_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));
}

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)
{
}

/*
 * 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;

	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,
		unsigned long tls)
{
	struct pt_regs *childregs;

	childregs = task_pt_regs(p);

	if (unlikely(p->flags & PF_KTHREAD)) {
		/* 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 = *current_pt_regs();
		if (usp)
			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;
}