/*
   * arch/xtensa/kernel/process.c
   *
   * Xtensa Processor version.
   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file "COPYING" in the main directory of this archive
   * for more details.
   *
   * Copyright (C) 2001 - 2005 Tensilica Inc.
   *
   * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
   * Chris Zankel <chris@zankel.net>
   * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
   * Kevin Chea
   */

  #include <linux/errno.h>
  #include <linux/sched.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/smp.h>

  #include <linux/stddef.h>
  #include <linux/unistd.h>
  #include <linux/ptrace.h>

  #include <linux/elf.h>
  #include <linux/init.h>
  #include <linux/prctl.h>
  #include <linux/init_task.h>
  #include <linux/module.h>
  #include <linux/mqueue.h>

  #include <linux/fs.h>

  #include <linux/slab.h>

  
  #include <asm/pgtable.h>
  #include <asm/uaccess.h>
  #include <asm/system.h>
  #include <asm/io.h>
  #include <asm/processor.h>
  #include <asm/platform.h>
  #include <asm/mmu.h>
  #include <asm/irq.h>

  #include <linux/atomic.h>

  #include <asm/asm-offsets.h>

  #include <asm/regs.h>

  
  extern void ret_from_fork(void);

  struct task_struct *current_set[NR_CPUS] = {&init_task, };

  void (*pm_power_off)(void) = NULL;
  EXPORT_SYMBOL(pm_power_off);

  #if XTENSA_HAVE_COPROCESSORS
  
  void coprocessor_release_all(struct thread_info *ti)
  {
  	unsigned long cpenable;
  	int i;
  
  	/* Make sure we don't switch tasks during this operation. */
  
  	preempt_disable();
  
  	/* Walk through all cp owners and release it for the requested one. */
  
  	cpenable = ti->cpenable;
  
  	for (i = 0; i < XCHAL_CP_MAX; i++) {
  		if (coprocessor_owner[i] == ti) {
  			coprocessor_owner[i] = 0;
  			cpenable &= ~(1 << i);
  		}
  	}
  
  	ti->cpenable = cpenable;
  	coprocessor_clear_cpenable();
  
  	preempt_enable();
  }
  
  void coprocessor_flush_all(struct thread_info *ti)
  {
  	unsigned long cpenable;
  	int i;
  
  	preempt_disable();
  
  	cpenable = ti->cpenable;
  
  	for (i = 0; i < XCHAL_CP_MAX; i++) {
  		if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
  			coprocessor_flush(ti, i);
  		cpenable >>= 1;
  	}
  
  	preempt_enable();
  }
  
  #endif

  /*
   * Powermanagement idle function, if any is provided by the platform.
   */
  
  void cpu_idle(void)
  {
    	local_irq_enable();
  
  	/* endless idle loop with no priority at all */
  	while (1) {
  		while (!need_resched())
  			platform_idle();

  		preempt_enable_no_resched();

  		schedule();

  		preempt_disable();

  	}
  }
  
  /*

   * This is called when the thread calls exit().

   */

  void exit_thread(void)
  {

  #if XTENSA_HAVE_COPROCESSORS
  	coprocessor_release_all(current_thread_info());
  #endif

  }

  /*
   * Flush thread state. This is called when a thread does an execve()
   * Note that we flush coprocessor registers for the case execve fails.
   */

  void flush_thread(void)
  {

  #if XTENSA_HAVE_COPROCESSORS
  	struct thread_info *ti = current_thread_info();
  	coprocessor_flush_all(ti);
  	coprocessor_release_all(ti);
  #endif
  }
  
  /*
   * This is called before the thread is copied. 
   */
  void prepare_to_copy(struct task_struct *tsk)
  {
  #if XTENSA_HAVE_COPROCESSORS
  	coprocessor_flush_all(task_thread_info(tsk));
  #endif

  }
  
  /*
   * Copy thread.
   *
   * The stack layout for the new thread looks like this:
   *
   *	+------------------------+ <- sp in childregs (= tos)
   *	|       childregs        |
   *	+------------------------+ <- thread.sp = sp in dummy-frame
   *	|      dummy-frame       |    (saved in dummy-frame spill-area)
   *	+------------------------+
   *
   * We create a dummy frame to return to ret_from_fork:
   *   a0 points to ret_from_fork (simulating a call4)
   *   sp points to itself (thread.sp)
   *   a2, a3 are unused.
   *
   * Note: This is a pristine frame, so we don't need any spill region on top of
   *       childregs.
   */

  int copy_thread(unsigned long clone_flags, unsigned long usp,

  		unsigned long unused,
                  struct task_struct * p, struct pt_regs * regs)
  {
  	struct pt_regs *childregs;

  	struct thread_info *ti;

  	unsigned long tos;
  	int user_mode = user_mode(regs);
  
  	/* Set up new TSS. */

  	tos = (unsigned long)task_stack_page(p) + THREAD_SIZE;

  	if (user_mode)
  		childregs = (struct pt_regs*)(tos - PT_USER_SIZE);
  	else
  		childregs = (struct pt_regs*)tos - 1;
  
  	*childregs = *regs;
  
  	/* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
  	*((int*)childregs - 3) = (unsigned long)childregs;
  	*((int*)childregs - 4) = 0;
  
  	childregs->areg[1] = tos;
  	childregs->areg[2] = 0;
  	p->set_child_tid = p->clear_child_tid = NULL;
  	p->thread.ra = MAKE_RA_FOR_CALL((unsigned long)ret_from_fork, 0x1);
  	p->thread.sp = (unsigned long)childregs;

  	if (user_mode(regs)) {
  
  		int len = childregs->wmask & ~0xf;
  		childregs->areg[1] = usp;
  		memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
  		       &regs->areg[XCHAL_NUM_AREGS - len/4], len);

  // FIXME: we need to set THREADPTR in thread_info...

  		if (clone_flags & CLONE_SETTLS)
  			childregs->areg[2] = childregs->areg[6];
  
  	} else {
  		/* In kernel space, we start a new thread with a new stack. */
  		childregs->wmask = 1;
  	}

  
  #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
  	ti = task_thread_info(p);
  	ti->cpenable = 0;
  #endif

  	return 0;
  }
  
  
  /*

   * These bracket the sleeping functions..
   */
  
  unsigned long get_wchan(struct task_struct *p)
  {
  	unsigned long sp, pc;

  	unsigned long stack_page = (unsigned long) task_stack_page(p);

  	int count = 0;
  
  	if (!p || p == current || p->state == TASK_RUNNING)
  		return 0;
  
  	sp = p->thread.sp;
  	pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
  
  	do {
  		if (sp < stack_page + sizeof(struct task_struct) ||
  		    sp >= (stack_page + THREAD_SIZE) ||
  		    pc == 0)
  			return 0;
  		if (!in_sched_functions(pc))
  			return pc;
  
  		/* Stack layout: sp-4: ra, sp-3: sp' */
  
  		pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
  		sp = *(unsigned long *)sp - 3;
  	} while (count++ < 16);
  	return 0;
  }
  
  /*

   * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
   * of processor registers.  Besides different ordering,
   * xtensa_gregset_t contains non-live register information that
   * 'struct pt_regs' does not.  Exception handling (primarily) uses
   * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
   *
   */

  void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)

  {

  	unsigned long wb, ws, wm;
  	int live, last;
  
  	wb = regs->windowbase;
  	ws = regs->windowstart;
  	wm = regs->wmask;
  	ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
  
  	/* Don't leak any random bits. */
  
  	memset(elfregs, 0, sizeof (elfregs));

  	/* Note:  PS.EXCM is not set while user task is running; its
  	 * being set in regs->ps is for exception handling convenience.
  	 */
  
  	elfregs->pc		= regs->pc;

  	elfregs->ps		= (regs->ps & ~(1 << PS_EXCM_BIT));

  	elfregs->lbeg		= regs->lbeg;
  	elfregs->lend		= regs->lend;
  	elfregs->lcount		= regs->lcount;
  	elfregs->sar		= regs->sar;

  	elfregs->windowstart	= ws;

  	live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
  	last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
  	memcpy(elfregs->a, regs->areg, live * 4);
  	memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);

  }

  int dump_fpu(void)

  {

  	return 0;
  }

  
  asmlinkage
  long xtensa_clone(unsigned long clone_flags, unsigned long newsp,
                    void __user *parent_tid, void *child_tls,
                    void __user *child_tid, long a5,
                    struct pt_regs *regs)
  {
          if (!newsp)
                  newsp = regs->areg[1];
          return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
  }
  
  /*

   * xtensa_execve() executes a new program.
   */

  
  asmlinkage

  long xtensa_execve(const char __user *name,
  		   const char __user *const __user *argv,
                     const char __user *const __user *envp,

                     long a3, long a4, long a5,
                     struct pt_regs *regs)
  {
  	long error;
  	char * filename;
  
  	filename = getname(name);
  	error = PTR_ERR(filename);
  	if (IS_ERR(filename))
  		goto out;

  	error = do_execve(filename, argv, envp, regs);

  	putname(filename);
  out:
  	return error;
  }