arch/c6x/kernel/process.c

   1 /*
   2  *  Port on Texas Instruments TMS320C6x architecture
   3  *
   4  *  Copyright (C) 2004, 2006, 2009, 2010, 2011 Texas Instruments Incorporated
   5  *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License version 2 as
   9  *  published by the Free Software Foundation.
  10  *
  11  */
  12 #include <linux/module.h>
  13 #include <linux/unistd.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/init_task.h>
  16 #include <linux/tick.h>
  17 #include <linux/mqueue.h>
  18 #include <linux/syscalls.h>
  19 #include <linux/reboot.h>
  20
  21 #include <asm/syscalls.h>
  22
  23 /* hooks for board specific support */
  24 void    (*c6x_restart)(void);
  25 void    (*c6x_halt)(void);
  26
  27 extern asmlinkage void ret_from_fork(void);
  28 extern asmlinkage void ret_from_kernel_thread(void);
  29
  30 /*
  31  * power off function, if any
  32  */
  33 void (*pm_power_off)(void);
  34 EXPORT_SYMBOL(pm_power_off);
  35
  36 static void c6x_idle(void)
  37 {
  38         unsigned long tmp;
  39
  40         /*
  41          * Put local_irq_enable and idle in same execute packet
  42          * to make them atomic and avoid race to idle with
  43          * interrupts enabled.
  44          */
  45         asm volatile ("   mvc .s2 CSR,%0\n"
  46                       "   or  .d2 1,%0,%0\n"
  47                       "   mvc .s2 %0,CSR\n"
  48                       "|| idle\n"
  49                       : "=b"(tmp));
  50 }
  51
  52 /*
  53  * The idle loop for C64x
  54  */
  55 void cpu_idle(void)
  56 {
  57         /* endless idle loop with no priority at all */
  58         while (1) {
  59                 tick_nohz_idle_enter();
  60                 rcu_idle_enter();
  61                 while (1) {
  62                         local_irq_disable();
  63                         if (need_resched()) {
  64                                 local_irq_enable();
  65                                 break;
  66                         }
  67                         c6x_idle(); /* enables local irqs */
  68                 }
  69                 rcu_idle_exit();
  70                 tick_nohz_idle_exit();
  71
  72                 preempt_enable_no_resched();
  73                 schedule();
  74                 preempt_disable();
  75         }
  76 }
  77
  78 static void halt_loop(void)
  79 {
  80         printk(KERN_EMERG "System Halted, OK to turn off power\n");
  81         local_irq_disable();
  82         while (1)
  83                 asm volatile("idle\n");
  84 }
  85
  86 void machine_restart(char *__unused)
  87 {
  88         if (c6x_restart)
  89                 c6x_restart();
  90         halt_loop();
  91 }
  92
  93 void machine_halt(void)
  94 {
  95         if (c6x_halt)
  96                 c6x_halt();
  97         halt_loop();
  98 }
  99
 100 void machine_power_off(void)
 101 {
 102         if (pm_power_off)
 103                 pm_power_off();
 104         halt_loop();
 105 }
 106
 107 void flush_thread(void)
 108 {
 109 }
 110
 111 void exit_thread(void)
 112 {
 113 }
 114
 115 /*
 116  * Do necessary setup to start up a newly executed thread.
 117  */
 118 void start_thread(struct pt_regs *regs, unsigned int pc, unsigned long usp)
 119 {
 120         /*
 121          * The binfmt loader will setup a "full" stack, but the C6X
 122          * operates an "empty" stack. So we adjust the usp so that
 123          * argc doesn't get destroyed if an interrupt is taken before
 124          * it is read from the stack.
 125          *
 126          * NB: Library startup code needs to match this.
 127          */
 128         usp -= 8;
 129
 130         set_fs(USER_DS);
 131         regs->pc  = pc;
 132         regs->sp  = usp;
 133         regs->tsr |= 0x40; /* set user mode */
 134         current->thread.usp = usp;
 135 }
 136
 137 /*
 138  * Copy a new thread context in its stack.
 139  */
 140 int copy_thread(unsigned long clone_flags, unsigned long usp,
 141                 unsigned long ustk_size,
 142                 struct task_struct *p)
 143 {
 144         struct pt_regs *childregs;
 145
 146         childregs = task_pt_regs(p);
 147
 148         if (unlikely(p->flags & PF_KTHREAD)) {
 149                 /* case of  __kernel_thread: we return to supervisor space */
 150                 memset(childregs, 0, sizeof(struct pt_regs));
 151                 childregs->sp = (unsigned long)(childregs + 1);
 152                 p->thread.pc = (unsigned long) ret_from_kernel_thread;
 153                 childregs->a0 = usp;            /* function */
 154                 childregs->a1 = ustk_size;      /* argument */
 155         } else {
 156                 /* Otherwise use the given stack */
 157                 *childregs = *current_pt_regs();
 158                 if (usp)
 159                         childregs->sp = usp;
 160                 p->thread.pc = (unsigned long) ret_from_fork;
 161         }
 162
 163         /* Set usp/ksp */
 164         p->thread.usp = childregs->sp;
 165         thread_saved_ksp(p) = (unsigned long)childregs - 8;
 166         p->thread.wchan = p->thread.pc;
 167 #ifdef __DSBT__
 168         {
 169                 unsigned long dp;
 170
 171                 asm volatile ("mv .S2 b14,%0\n" : "=b"(dp));
 172
 173                 thread_saved_dp(p) = dp;
 174                 if (usp == -1)
 175                         childregs->dp = dp;
 176         }
 177 #endif
 178         return 0;
 179 }
 180
 181 unsigned long get_wchan(struct task_struct *p)
 182 {
 183         return p->thread.wchan;
 184 }