m4_init/3rd/libopencm3/lib/lm3s/rcc.c

/** @defgroup rcc_file RCC Controller

@brief <b>LM3S RCC Controller</b>

@ingroup LM3Sxx

@version 1.0.0

@author @htmlonly &copy; @endhtmlonly 2015
Daniele Lacamera \<root at danielinux dot net\>

@date 21 November 2015

LGPL License Terms @ref lgpl_license
*/
/*
 * This file is part of the libopencm3 project.
 *
 * Copyright (C) 2015 Daniele Lacamera <root@danielinux.net>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdint.h>
#include <libopencm3/lm3s/rcc.h>
#include <libopencm3/cm3/sync.h>

int rcc_clock_setup_in_xtal_8mhz_out_50mhz(void)
{
    uint32_t rcc = RCC_RESET_VALUE;
    uint32_t rcc2 = RCC2_RESET_VALUE;

    /* Stage 0: Reset values applied */
    RCC_CR = rcc;
    RCC2_CR = rcc2;
    __dmb();

    /* Stage 1: Reset Oscillators and select configured values */
    RCC_CR = RCC_SYSDIV_50MHZ | RCC_PWMDIV_64 | RCC_XTAL_8MHZ_400MHZ | RCC_USEPWMDIV;
    RCC2_CR = (4 - 1) << RCC2_SYSDIV2_SHIFT;
    __dmb();

    /* Stage 2: Power on oscillators */
    rcc  &= ~RCC_OFF;
    rcc2 &= ~RCC2_OFF;
    RCC_CR = rcc;
    RCC2_CR = rcc2;
    __dmb();

    /* Stage 3: Set USESYSDIV */
    rcc |= RCC_BYPASS | RCC_USESYSDIV;
    RCC_CR = rcc;
    __dmb();

    /* Stage 4: Wait for PLL raw interrupt */
    while ((RCC_RIS & RIS_PLLLRIS) == 0)
        ;

    /* Stage 5: Disable bypass */
    rcc  &= ~RCC_BYPASS;
    rcc2 &= ~RCC2_BYPASS;
    RCC_CR = rcc;
    RCC2_CR = rcc2;
    __dmb();
    return 0;
}