/****************************************************************************
 * arch/xtensa/src/common/xtensa_usestack.c
 *
 *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <sched.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/arch.h>

#include "xtensa.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* XTENSA requires at least a 4-byte stack alignment.  For floating point use,
 * however, the stack must be aligned to 8-byte addresses.
 */

#ifdef CONFIG_LIBC_FLOATINGPOINT
#  define STACK_ALIGNMENT   8
#else
#  define STACK_ALIGNMENT   4
#endif

/* Stack alignment macros */

#define STACK_ALIGN_MASK    (STACK_ALIGNMENT-1)
#define STACK_ALIGN_DOWN(a) ((a) & ~STACK_ALIGN_MASK)
#define STACK_ALIGN_UP(a)   (((a) + STACK_ALIGN_MASK) & ~STACK_ALIGN_MASK)

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_use_stack
 *
 * Description:
 *   Setup up stack-related information in the TCB using pre-allocated stack
 *   memory.  This function is called only from task_init() when a task or
 *   kernel thread is started (never for pthreads).
 *
 *   The following TCB fields must be initialized:
 *
 *   - adj_stack_size: Stack size after adjustment for hardware,
 *     processor, etc.  This value is retained only for debug
 *     purposes.
 *   - stack_alloc_ptr: Pointer to allocated stack
 *   - adj_stack_ptr: Adjusted stack_alloc_ptr for HW.  The
 *     initial value of the stack pointer.
 *
 * Inputs:
 *   - tcb: The TCB of new task
 *   - stack_size:  The allocated stack size.
 *
 *   NOTE:  Unlike up_stack_create() and up_stack_release, this function
 *   does not require the task type (ttype) parameter.  The TCB flags will
 *   always be set to provide the task type to up_use_stack() if it needs
 *   that information.
 *
 ****************************************************************************/

int up_use_stack(struct tcb_s *tcb, void *stack, size_t stack_size)
{
  size_t top_of_stack;
  size_t size_of_stack;

  /* Is there already a stack allocated? */

  if (tcb->stack_alloc_ptr)
    {
      /* Yes.. Release the old stack allocation */

      up_release_stack(tcb, tcb->flags & TCB_FLAG_TTYPE_MASK);
    }

  /* Save the new stack allocation */

  tcb->stack_alloc_ptr = stack;

  /* XTENSA uses a push-down stack:  the stack grows toward loweraddresses in
   * memory.  The stack pointer register, points to the lowest, valid work
   * address (the "top" of the stack).  Items on the stack are referenced
   * as positive word offsets from sp.
   */

  top_of_stack = (uint32_t)tcb->stack_alloc_ptr + stack_size - 4;

  /* The XTENSA stack must be aligned at word (4 byte) or double word (8 byte)
   * boundaries. If necessary top_of_stack must be rounded down to the
   * next boundary
   */

  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
  size_of_stack = top_of_stack - (uint32_t)tcb->stack_alloc_ptr + 4;

  /* Save the adjusted stack values in the struct tcb_s */

  tcb->adj_stack_ptr  = (uint32_t *)top_of_stack;
  tcb->adj_stack_size = size_of_stack;

  return OK;
}