path: root/nuttx/arch/arm/src/lpc31xx/lpc31_lowputc.c

/****************************************************************************
 * arch/arm/src/lpc31xx/lpc31_lowputc.c
 *
 *   Copyright (C) 2009-2010, 2012 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 <debug.h>

#include <nuttx/arch.h>

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

#include "lpc31_cgudrvr.h"
#include "lpc31_uart.h"

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

/* Configuration ************************************************************/

/* Is the UART enabled? */

#ifdef CONFIG_LPC31_UART
#  define HAVE_UART 1

/* Is it a serial console? */

#  ifdef CONFIG_UART_SERIAL_CONSOLE
#    define HAVE_CONSOLE 1

     /* Is initialization performed by up_earlyserialinit()?  Or is UART
      * initialization suppressed?
      */

#    if defined(USE_EARLYSERIALINIT) || defined(CONFIG_SUPPRESS_UART_CONFIG)
#      undef NEED_LOWSETUP
#    else
#      define NEED_LOWSETUP 1
#    endif
#  else
#      undef HAVE_CONSOLE
#      undef NEED_LOWSETUP
#  endif

#else
#  undef HAVE_UART
#  undef HAVE_CONSOLE
#  undef NEED_LOWSETUP
#endif

/****************************************************************************
 * Private Types
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

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

/****************************************************************************
 * Name: up_waittxready
 ****************************************************************************/

#ifdef HAVE_CONSOLE
static inline void up_waittxready(void)
{
  int tmp;

  /* Limit how long we will wait for the TX available condition */

  for (tmp = 1000 ; tmp > 0 ; tmp--)
    {
      /* Check if the tranmitter holding register (THR) is empty */

      if ((getreg32(LPC31_UART_LSR) & UART_LSR_THRE) != 0)
        {
          /* The THR is empty, return */

          break;
        }
    }
}
#endif

/****************************************************************************
 * Name: up_configbaud
 ****************************************************************************/

#ifdef NEED_LOWSETUP
static inline void up_configbaud(void)
{
  /* In a buckled-up, embedded system, there is no reason to constantly
   * calculate the following.  The calculation can be skipped if the
   * MULVAL, DIVADDVAL, and DIVISOR values are provided in the configuration
   * file.
   */

#ifndef CONFIG_LPC31_UART_MULVAL
  uint32_t qtrclk;
  uint32_t regval;

  /* Test values calculated for every multiplier/divisor combination */

  uint32_t tdiv;
  uint32_t terr;
  int      tmulval;
  int      tdivaddval;

  /* Optimal multiplier/divider values */

  uint32_t div       = 0;
  uint32_t err       = 100000;
  int      mulval    = 1;
  int      divaddval = 0;

  /* Baud is generated using FDR and DLL-DLM registers
   *
   *   baud = clock * (mulval/(mulval+divaddval) / (16 * div)
   *
   * Or
   *
   *   div = (clock/16) * (mulval/(mulval+divaddval) / baud
   *
   * Where mulval    = Fractional divider multiplier
   *       divaddval = Fractional divider pre-scale div
   *       div       = DLL-DLM divisor
   */

  /* Get UART block clock divided by 16 */

  qtrclk = lpc31_clkfreq(CLKID_UARTUCLK, DOMAINID_UART) >> 4;

  /* Try every valid multiplier, tmulval (or until a perfect
   * match is found).
   */

  for (tmulval = 1 ; tmulval <= 15 && err > 0; tmulval++)
    {
      /* Try every valid pre-scale div, tdivaddval (or until a perfect
       * match is found).
       */

      for (tdivaddval = 0 ; tdivaddval <= 15 && err > 0; tdivaddval++)
        {
          /* Calculate the divisor with these fractional divider settings */

          uint32_t tmp = (tmulval * qtrclk) / ((tmulval + tdivaddval));
          tdiv         = (tmp + (CONFIG_UART_BAUD>>1)) / CONFIG_UART_BAUD;

          /* Check if this candidate divisor is within a valid range */

          if (tdiv > 2 && tdiv < 0x10000)
            {
              /* Calculate the actual baud and the error */

              uint32_t actualbaud = tmp / tdiv;

              if (actualbaud <= CONFIG_UART_BAUD)
                {
                  terr = CONFIG_UART_BAUD - actualbaud;
                }
              else
                {
                  terr = actualbaud - CONFIG_UART_BAUD;
                }

              /* Is this the smallest error we have encountered? */

              if (terr < err)
                {
                  /* Yes, save these settings as the new, candidate optimal settings */

                  mulval     = tmulval ;
                  divaddval = tdivaddval;
                  div       = tdiv;
                  err       = terr;
                }
            }
        }
    }

    /* Set the Divisor Latch Access Bit (DLAB) to enable DLL/DLM access */

    regval  = getreg32(LPC31_UART_LCR);
    regval |= UART_LCR_DLAB;
    putreg32(regval, LPC31_UART_LCR);

    /* Configure the MS and LS DLAB registers */

    putreg32(div & UART_DLL_MASK, LPC31_UART_DLL);
    putreg32((div >> 8) & UART_DLL_MASK, LPC31_UART_DLM);

    regval &= ~UART_LCR_DLAB;
    putreg32(regval, LPC31_UART_LCR);

    /* Configure the Fractional Divider Register (FDR) */

    putreg32((mulval    << UART_FDR_MULVAL_SHIFT) |
             (divaddval << UART_FDR_DIVADDVAL_SHIFT),
             LPC31_UART_FDR);
#else
    /* Set the Divisor Latch Access Bit (DLAB) to enable DLL/DLM access */

    regval  = getreg32(LPC31_UART_LCR);
    regval |= UART_LCR_DLAB;
    putreg32(regval, LPC31_UART_LCR);

    /* Configure the MS and LS DLAB registers */

    putreg32(CONFIG_LPC31_UART_DIVISOR & UART_DLL_MASK, LPC31_UART_DLL);
    putreg32((CONFIG_LPC31_UART_DIVISOR >> 8) & UART_DLL_MASK, LPC31_UART_DLM);

    regval &= ~UART_LCR_DLAB;
    putreg32(regval, LPC31_UART_LCR);

    /* Configure the Fractional Divider Register (FDR) */

    putreg32((CONFIG_LPC31_UART_MULVAL    << UART_FDR_MULVAL_SHIFT) |
             (CONFIG_LPC31_UART_DIVADDVAL << UART_FDR_DIVADDVAL_SHIFT),
             LPC31_UART_FDR);
#endif
}
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/
/****************************************************************************
 * Name: lpc31_lowsetup
 *
 * Description:
 *   Called early in up_boot.  Performs chip-common low level initialization.
 *
 ****************************************************************************/

void lpc31_lowsetup(void)
{
#ifdef NEED_LOWSETUP
  uint32_t regval;

  /* Enable UART system clock */

  lpc31_enableclock(CLKID_UARTAPBCLK);
  lpc31_enableclock(CLKID_UARTUCLK);

  /* Clear fifos */

  putreg32((UART_FCR_RXFIFORST|UART_FCR_TXFIFORST), LPC31_UART_FCR);

  /* Set trigger */

  putreg32((UART_FCR_FIFOENABLE|UART_FCR_RXTRIGLEVEL_16), LPC31_UART_FCR);

  /* Set up the LCR */

  regval = 0;

#if CONFIG_UART_BITS == 5
  regval |= UART_LCR_WDLENSEL_5BITS;
#elif CONFIG_UART_BITS == 6
  regval |= UART_LCR_WDLENSEL_6BITS;
#elif CONFIG_UART_BITS == 7
  regval |= UART_LCR_WDLENSEL_7BITS;
#else
  regval |= UART_LCR_WDLENSEL_8BITS;
#endif

#if CONFIG_UART_2STOP > 0
  regval |= UART_LCR_NSTOPBITS;
#endif

#if CONFIG_UART_PARITY == 1
  regval |= UART_LCR_PAREN;
#elif CONFIG_UART_PARITY == 2
  regval |= (UART_LCR_PAREVEN|UART_LCR_PAREN);
#endif
  putreg32(regval, LPC31_UART_LCR);

  /* Set the BAUD divisor */

  up_configbaud();

  /* Configure the FIFOs */

  putreg32((UART_FCR_RXTRIGLEVEL_16|UART_FCR_TXFIFORST|
            UART_FCR_RXFIFORST|UART_FCR_FIFOENABLE),
           LPC31_UART_FCR);

  /* The NuttX serial driver waits for the first THRE interrrupt before
   * sending serial data... However, it appears that the lpc313x hardware
   * does not generate that interrupt until a transition from not-empty
   * to empty.  So, the current kludge here is to send one NULL at
   * startup to kick things off.
   */

  putreg32('\0', LPC31_UART_THR);
#endif
}

/****************************************************************************
 * Name: up_lowputc
 *
 * Description:
 *   Provide priority, low-level access to support OS debug  writes
 *
 ****************************************************************************/

void up_lowputc(char ch)
{
#ifdef HAVE_CONSOLE
  up_waittxready();
  putreg32((uint32_t)ch, LPC31_UART_THR);
#endif
}