source: rtems/bsps/arm/lpc176x/start/system-clocks.c

/* SPDX-License-Identifier: BSD-2-Clause */

/**
 * @file
 *
 * @ingroup RTEMSBSPsARMLPC176X_clocks
 *
 * @brief System clocks.
 */

/*
 * Copyright (C) 2008, 2012 embedded brains GmbH & Co. KG
 *
 * 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.
 *
 * 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.
 */

#include <bsp.h>
#include <bsp/system-clocks.h>

/**
 * @brief Internal RC oscillator frequency in [Hz].
 */
#define LPC176X_OSCILLATOR_INTERNAL 4000000u

#ifndef LPC176X_OSCILLATOR_MAIN
#error "unknown main oscillator frequency"
#endif

#ifndef LPC176X_OSCILLATOR_RTC
#error "unknown RTC oscillator frequency"
#endif

inline unsigned lpc176x_sysclk( void );

void lpc176x_timer_initialize( void )
{
  /* Reset timer */
  LPC176X_T1TCR = TCR_RST;
  /* Set timer mode */
  LPC176X_T1CTCR = 0u;
  /* Set prescaler to zero */
  LPC176X_T1PR = 0u;
  /* Reset all interrupt flags */
  LPC176X_T1IR = 0xffU;
  /* Do not stop on a match */
  LPC176X_T1MCR = 0u;
  /* No captures */
  LPC176X_T1CCR = 0u;
  /* Start timer */
  LPC176X_T1TCR = TCR_EN;
}

void lpc176x_micro_seconds_delay( const unsigned us )
{
  const unsigned start = lpc176x_get_timer1();
  const unsigned delay = us * ( LPC176X_PCLK / 1000000u );
  unsigned       elapsed = 0u;

  do {
    elapsed = lpc176x_get_timer1() - start;
  } while ( elapsed < delay );
}

unsigned lpc176x_sysclk( void )
{
  return ( LPC176X_SCB.clksrcsel & LPC176X_SCB_CLKSRCSEL_CLKSRC ) != 0u ?
         LPC176X_OSCILLATOR_MAIN : LPC176X_OSCILLATOR_INTERNAL;
}

unsigned lpc176x_pllclk( void )
{
  const unsigned sysclk = lpc176x_sysclk();
  const unsigned pllstat = ( LPC176X_SCB.pll_0 ).stat;
  const unsigned enabled_and_locked = LPC176X_PLL_STAT_PLLE |
                                      LPC176X_PLL_STAT_PLOCK;
  unsigned pllclk = 0u;

  if ( ( pllstat & enabled_and_locked ) == enabled_and_locked ) {
    unsigned m = LPC176X_PLL_SEL_MSEL_GET( pllstat ) + 1u;
    pllclk = sysclk * m;
  }

  /* else implies that the pllstat is unlocked. Also,
     there is nothing to do. */

  return pllclk;
}

unsigned lpc176x_cclk( void )
{
  const unsigned cclksel = LPC176X_SCB.cclksel;
  unsigned       cclk_in = 0u;
  unsigned       cclk = 0u;

  if ( ( cclksel & LPC176X_SCB_CCLKSEL_CCLKSEL ) != 0u ) {
    cclk_in = lpc176x_pllclk();
  } else {
    cclk_in = lpc176x_sysclk();
  }

  cclk = cclk_in / LPC176X_SCB_CCLKSEL_CCLKDIV_GET( cclksel );

  return cclk;
}

uint32_t _CPU_Counter_frequency(void)
{
  return LPC176X_PCLK;
}

CPU_Counter_ticks _CPU_Counter_read( void )
{
  return lpc176x_get_timer1();
}