/****************************************************************************
 * arch/arm/src/lm3s/lm3s_syscontrol.c
 * arch/arm/src/chip/lm3s_syscontrol.c
 *
 *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * 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 <stdint.h>
#include <assert.h>
#include <debug.h>

#include <nuttx/init.h>
#include <arch/board/board.h>

#include "up_arch.h"
#include "up_internal.h"
#include "lm3s_internal.h"

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

#define RCC_OSCMASK   (SYSCON_RCC_IOSCDIS|SYSCON_RCC_MOSCDIS)
#define RCC_XTALMASK  (SYSCON_RCC_XTAL_MASK|SYSCON_RCC_OSCSRC_MASK|SYSCON_RCC_PWRDN)
#define RCC2_XTALMASK (SYSCON_RCC2_USERCC2|SYSCON_RCC2_OSCSRC2_MASK|SYSCON_RCC2_PWRDN2)
#define RCC_DIVMASK   (SYSCON_RCC_SYSDIV_MASK|SYSCON_RCC_USESYSDIV|SYSCON_RCC_IOSCDIS|SYSCON_RCC_MOSCDIS)
#define RCC2_DIVMASK  (SYSCON_RCC2_SYSDIV2_MASK)
#define FAST_OSCDELAY (512*1024)
#define SLOW_OSCDELAY (4*1024)
#define PLLLOCK_DELAY (32*1024)

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Public Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: lm3s_delay
 *
 * Description:
 *   Wait for the newly selected oscillator(s) to settle.  This is tricky because
 *   the time that we wait can be significant and is determined by the previous
 *   clock setting, not the one that we are configuring.
 *
 ****************************************************************************/

static inline void lm3s_delay(uint32_t delay)
{
  __asm__ __volatile__("1:\n"
                       "\tsubs  %0, #1\n"
                       "\tbne   1b\n"
                       : "=r"(delay) : "r"(delay));
}

/****************************************************************************
 * Name: lm3s_oscdelay
 *
 * Description:
 *   Wait for the newly selected oscillator(s) to settle.  This is tricky because
 *   the time that we wait can be significant and is determined by the previous
 *   clock setting, not the one that we are configuring.
 *
 ****************************************************************************/

static inline void lm3s_oscdelay(uint32_t rcc, uint32_t rcc2)
{
  /* Wait for the oscillator  to stabilize.  A smaller delay is used if the
   * current clock rate is very slow.
   */

  uint32_t delay   = FAST_OSCDELAY;

  /* Are we currently using RCC2? */

  if ((rcc2 & SYSCON_RCC2_USERCC2) != 0)
    {
      uint32_t rcc2src = rcc2 & SYSCON_RCC2_OSCSRC2_MASK;
      if ((rcc2src == SYSCON_RCC2_OSCSRC2_30KHZ) ||
          (rcc2src == SYSCON_RCC2_OSCSRC2_32KHZ))
        {
          delay = SLOW_OSCDELAY;
        }
    }

  /* No.. using srce in RCC */

  else
    {
      uint32_t rccsrc  = rcc  & SYSCON_RCC_OSCSRC_MASK;
      if (rccsrc == SYSCON_RCC_OSCSRC_30KHZ)
        {
          delay = SLOW_OSCDELAY;
        }
    }

  /* Then delay that number of loops */

  lm3s_delay(delay);
}

/****************************************************************************
 * Name: lm3s_plllock
 *
 * Description:
 *   The new RCC values have been selected... wait for the PLL to lock on
 *
 ****************************************************************************/

static inline void lm3s_plllock(void)
{
  uint32_t delay;

  /* Loop until the lock is achieved or until a timeout occurs */

  for (delay = PLLLOCK_DELAY; delay > 0; delay--)
    {
      /* Check if the PLL is locked on */

      if ((getreg32(LM3S_SYSCON_RIS) & SYSCON_RIS_PLLLRIS) != 0)
        {
          /* Yes.. return now */

          return;
        }
    }

  /* If we get here, then PLL lock was not achieved */
}

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

/****************************************************************************
 * Name: lm3s_clockconfig
 *
 * Description:
 *   Called to change to new clock based on desired rcc and rcc2 settings.
 *   This is use to set up the initial clocking but can be used later to
 *   support slow clocked, low power consumption modes.
 *
 ****************************************************************************/

void lm3s_clockconfig(uint32_t newrcc, uint32_t newrcc2)
{
  uint32_t rcc;
  uint32_t rcc2;

  /* Get the current values of the RCC and RCC2 registers */

  rcc  = getreg32(LM3S_SYSCON_RCC);
  rcc2 = getreg32(LM3S_SYSCON_RCC2);

  /* Temporarily bypass the PLL and system clock dividers */

  rcc |= SYSCON_RCC_BYPASS;
  rcc &= ~(SYSCON_RCC_USESYSDIV);
  putreg32(rcc, LM3S_SYSCON_RCC);

  rcc2 |= SYSCON_RCC2_BYPASS2;
  putreg32(rcc2, LM3S_SYSCON_RCC2);

  /* We are probably using the main oscillator.  The main oscillator is disabled on
   * reset and so probably must be enabled here.  The internal oscillator is enabled
   * on rest and if that is selected, most likely nothing needs to be done.
   */

  if (((rcc & SYSCON_RCC_MOSCDIS) && !(newrcc & SYSCON_RCC_MOSCDIS)) ||
      ((rcc & SYSCON_RCC_IOSCDIS) && !(newrcc & SYSCON_RCC_IOSCDIS)))
    {
      /* Enable any selected osciallators (but don't disable any yet) */

      rcc &= (~RCC_OSCMASK | (newrcc & RCC_OSCMASK));
      putreg32(rcc, LM3S_SYSCON_RCC);

      /* Wait for the newly selected oscillator(s) to settle.  This is tricky because
       * the time that we wait can be significant and is determined by the previous
       * clock setting, not the one that we are configuring.
       */

      lm3s_oscdelay(rcc, rcc2);
    }

  /* Set the new crystal value, oscillator source and PLL configuration */

  rcc  &= ~RCC_XTALMASK;
  rcc  |= newrcc & RCC_XTALMASK;

  rcc2 &= ~RCC2_XTALMASK;
  rcc2 |= newrcc2 & RCC2_XTALMASK;

  /* Clear the PLL lock interrupt */

  putreg32(SYSCON_MISC_PLLLMIS, LM3S_SYSCON_MISC);

  /* Write the new RCC/RCC2 values.  Order depends upon whether RCC2 or RCC
   * is currently enabled.
   */

  if (rcc2 & SYSCON_RCC2_USERCC2)
    {
      putreg32(rcc2, LM3S_SYSCON_RCC2);
      putreg32(rcc, LM3S_SYSCON_RCC);
    }
    else
    {
      putreg32(rcc, LM3S_SYSCON_RCC);
      putreg32(rcc2, LM3S_SYSCON_RCC2);
    }

  /* Wait for the new crystal value and oscillator source to take effect */

  lm3s_delay(16);

  /* Set the requested system divider and disable the non-selected osciallators */

  rcc &= ~RCC_DIVMASK;
  rcc |= newrcc & RCC_DIVMASK;

  rcc2 &= ~RCC2_DIVMASK;
  rcc2 |= newrcc2 & RCC2_DIVMASK;

  /* Will the PLL output be used to clock the system? */

  if ((newrcc & SYSCON_RCC_BYPASS) == 0)
    {
      /* Yes, wail untill the PLL is locked */

      lm3s_plllock();

      /* Then enable the PLL */

      rcc  &= ~SYSCON_RCC_BYPASS;
      rcc2 &= ~SYSCON_RCC2_BYPASS2;
    }

  /* Now we can set the final RCC/RCC2 values */

  putreg32(rcc, LM3S_SYSCON_RCC);
  putreg32(rcc2, LM3S_SYSCON_RCC2);

  /* Wait for the system divider to be effective */

  lm3s_delay(6);
}

/****************************************************************************
 * Name: up_clockconfig
 *
 * Description:
 *   Called early in the bootsequence (before .data and .bss are available)
 *   in order to configure initial clocking.
 *
 ****************************************************************************/

void up_clockconfig(void)
{
#ifdef CONFIG_LM3S_REVA2
  /* Some early silicon returned an increase LDO voltage or 2.75V to work
   * around a PLL bug
   */

  putreg32(SYSCON_LPDOPCTL_2750MV, LM3S_SYSCON_LDOPCTL);
#endif

  /* Set the clocking to run with the default settings provided in the board.h
   * header file
   */

  lm3s_clockconfig(LM3S_RCC_VALUE, LM3S_RCC2_VALUE);
}

