1/*
  2 * arch/score/kernel/process.c
  3 *
  4 * Score Processor version.
  5 *
  6 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
  7 *  Chen Liqin <liqin.chen@sunplusct.com>
  8 *  Lennox Wu <lennox.wu@sunplusct.com>
  9 *
 10 * This program is free software; you can redistribute it and/or modify
 11 * it under the terms of the GNU General Public License as published by
 12 * the Free Software Foundation; either version 2 of the License, or
 13 * (at your option) any later version.
 14 *
 15 * This program is distributed in the hope that it will be useful,
 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 18 * GNU General Public License for more details.
 19 *
 20 * You should have received a copy of the GNU General Public License
 21 * along with this program; if not, see the file COPYING, or write
 22 * to the Free Software Foundation, Inc.,
 23 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 24 */
 25
 26#include <linux/module.h>
 27#include <linux/reboot.h>
 28#include <linux/elfcore.h>
 29#include <linux/pm.h>
 30
 31void (*pm_power_off)(void);
 32EXPORT_SYMBOL(pm_power_off);
 33
 34/* If or when software machine-restart is implemented, add code here. */
 35void machine_restart(char *command) {}
 36
 37/* If or when software machine-halt is implemented, add code here. */
 38void machine_halt(void) {}
 39
 40/* If or when software machine-power-off is implemented, add code here. */
 41void machine_power_off(void) {}
 42
 43/*
 44 * The idle thread. There's no useful work to be
 45 * done, so just try to conserve power and have a
 46 * low exit latency (ie sit in a loop waiting for
 47 * somebody to say that they'd like to reschedule)
 48 */
 49void __noreturn cpu_idle(void)
 50{
 51	/* endless idle loop with no priority at all */
 52	while (1) {
 53		while (!need_resched())
 54			barrier();
 55
 56		preempt_enable_no_resched();
 57		schedule();
 58		preempt_disable();
 59	}
 60}
 61
 62void ret_from_fork(void);
 63
 64void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 65{
 66	unsigned long status;
 67
 68	/* New thread loses kernel privileges. */
 69	status = regs->cp0_psr & ~(KU_MASK);
 70	status |= KU_USER;
 71	regs->cp0_psr = status;
 72	regs->cp0_epc = pc;
 73	regs->regs[0] = sp;
 74}
 75
 76void exit_thread(void) {}
 77
 78/*
 79 * When a process does an "exec", machine state like FPU and debug
 80 * registers need to be reset.  This is a hook function for that.
 81 * Currently we don't have any such state to reset, so this is empty.
 82 */
 83void flush_thread(void) {}
 84
 85/*
 86 * set up the kernel stack and exception frames for a new process
 87 */
 88int copy_thread(unsigned long clone_flags, unsigned long usp,
 89		unsigned long unused,
 90		struct task_struct *p, struct pt_regs *regs)
 91{
 92	struct thread_info *ti = task_thread_info(p);
 93	struct pt_regs *childregs = task_pt_regs(p);
 94
 95	p->set_child_tid = NULL;
 96	p->clear_child_tid = NULL;
 97
 98	*childregs = *regs;
 99	childregs->regs[7] = 0;		/* Clear error flag */
100	childregs->regs[4] = 0;		/* Child gets zero as return value */
101	regs->regs[4] = p->pid;
102
103	if (childregs->cp0_psr & 0x8) {	/* test kernel fork or user fork */
104		childregs->regs[0] = usp;		/* user fork */
105	} else {
106		childregs->regs[28] = (unsigned long) ti; /* kernel fork */
107		childregs->regs[0] = (unsigned long) childregs;
108	}
109
110	p->thread.reg0 = (unsigned long) childregs;
111	p->thread.reg3 = (unsigned long) ret_from_fork;
112	p->thread.cp0_psr = 0;
113
114	return 0;
115}
116
117/* Fill in the fpu structure for a core dump. */
118int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
119{
120	return 1;
121}
122
123static void __noreturn
124kernel_thread_helper(void *unused0, int (*fn)(void *),
125		 void *arg, void *unused1)
126{
127	do_exit(fn(arg));
128}
129
130/*
131 * Create a kernel thread.
132 */
133long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
134{
135	struct pt_regs regs;
136
137	memset(&regs, 0, sizeof(regs));
138
139	regs.regs[6] = (unsigned long) arg;
140	regs.regs[5] = (unsigned long) fn;
141	regs.cp0_epc = (unsigned long) kernel_thread_helper;
142	regs.cp0_psr = (regs.cp0_psr & ~(0x1|0x4|0x8)) | \
143			((regs.cp0_psr & 0x3) << 2);
144
145	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, \
146			0, &regs, 0, NULL, NULL);
147}
148
149unsigned long thread_saved_pc(struct task_struct *tsk)
150{
151	return task_pt_regs(tsk)->cp0_epc;
152}
153
154unsigned long get_wchan(struct task_struct *task)
155{
156	if (!task || task == current || task->state == TASK_RUNNING)
157		return 0;
158
159	if (!task_stack_page(task))
160		return 0;
161
162	return task_pt_regs(task)->cp0_epc;
163}
164
165unsigned long arch_align_stack(unsigned long sp)
166{
167	return sp;
168}