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		schedule_preempt_disabled();
 57	}
 58}
 59
 60void ret_from_fork(void);
 61
 62void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 63{
 64	unsigned long status;
 65
 66	/* New thread loses kernel privileges. */
 67	status = regs->cp0_psr & ~(KU_MASK);
 68	status |= KU_USER;
 69	regs->cp0_psr = status;
 70	regs->cp0_epc = pc;
 71	regs->regs[0] = sp;
 72}
 73
 74void exit_thread(void) {}
 75
 76/*
 77 * When a process does an "exec", machine state like FPU and debug
 78 * registers need to be reset.  This is a hook function for that.
 79 * Currently we don't have any such state to reset, so this is empty.
 80 */
 81void flush_thread(void) {}
 82
 83/*
 84 * set up the kernel stack and exception frames for a new process
 85 */
 86int copy_thread(unsigned long clone_flags, unsigned long usp,
 87		unsigned long unused,
 88		struct task_struct *p, struct pt_regs *regs)
 89{
 90	struct thread_info *ti = task_thread_info(p);
 91	struct pt_regs *childregs = task_pt_regs(p);
 92
 93	p->set_child_tid = NULL;
 94	p->clear_child_tid = NULL;
 95
 96	*childregs = *regs;
 97	childregs->regs[7] = 0;		/* Clear error flag */
 98	childregs->regs[4] = 0;		/* Child gets zero as return value */
 99	regs->regs[4] = p->pid;
100
101	if (childregs->cp0_psr & 0x8) {	/* test kernel fork or user fork */
102		childregs->regs[0] = usp;		/* user fork */
103	} else {
104		childregs->regs[28] = (unsigned long) ti; /* kernel fork */
105		childregs->regs[0] = (unsigned long) childregs;
106	}
107
108	p->thread.reg0 = (unsigned long) childregs;
109	p->thread.reg3 = (unsigned long) ret_from_fork;
110	p->thread.cp0_psr = 0;
111
112	return 0;
113}
114
115/* Fill in the fpu structure for a core dump. */
116int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
117{
118	return 1;
119}
120
121static void __noreturn
122kernel_thread_helper(void *unused0, int (*fn)(void *),
123		 void *arg, void *unused1)
124{
125	do_exit(fn(arg));
126}
127
128/*
129 * Create a kernel thread.
130 */
131long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
132{
133	struct pt_regs regs;
134
135	memset(&regs, 0, sizeof(regs));
136
137	regs.regs[6] = (unsigned long) arg;
138	regs.regs[5] = (unsigned long) fn;
139	regs.cp0_epc = (unsigned long) kernel_thread_helper;
140	regs.cp0_psr = (regs.cp0_psr & ~(0x1|0x4|0x8)) | \
141			((regs.cp0_psr & 0x3) << 2);
142
143	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, \
144			0, &regs, 0, NULL, NULL);
145}
146
147unsigned long thread_saved_pc(struct task_struct *tsk)
148{
149	return task_pt_regs(tsk)->cp0_epc;
150}
151
152unsigned long get_wchan(struct task_struct *task)
153{
154	if (!task || task == current || task->state == TASK_RUNNING)
155		return 0;
156
157	if (!task_stack_page(task))
158		return 0;
159
160	return task_pt_regs(task)->cp0_epc;
161}
162
163unsigned long arch_align_stack(unsigned long sp)
164{
165	return sp;
166}