arch/score/kernel/process.c

   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
  31 void (*pm_power_off)(void);
  32 EXPORT_SYMBOL(pm_power_off);
  33
  34 /* If or when software machine-restart is implemented, add code here. */
  35 void machine_restart(char *command) {}
  36
  37 /* If or when software machine-halt is implemented, add code here. */
  38 void machine_halt(void) {}
  39
  40 /* If or when software machine-power-off is implemented, add code here. */
  41 void 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  */
  49 void __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
  62 void ret_from_fork(void);
  63
  64 void 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
  76 void 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  */
  83 void flush_thread(void) {}
  84
  85 /*
  86  * set up the kernel stack and exception frames for a new process
  87  */
  88 int 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. */
 118 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 119 {
 120         return 1;
 121 }
 122
 123 static void __noreturn
 124 kernel_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  */
 133 long 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
 149 unsigned long thread_saved_pc(struct task_struct *tsk)
 150 {
 151         return task_pt_regs(tsk)->cp0_epc;
 152 }
 153
 154 unsigned 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
 165 unsigned long arch_align_stack(unsigned long sp)
 166 {
 167         return sp;
 168 }