/****************************************************************************
* arch/arm/src/samd/sam_lowputc.c
*
* Copyright (C) 2014 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* References:
* 1. "Atmel SAM D20J / SAM D20G / SAM D20E ARM-Based Microcontroller
* Datasheet", 42129J�SAM�12/2013
*
* 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 <stdbool.h>
#include "up_arch.h"
#include "sam_config.h"
#include "chip/sam_pm.h"
#include "chip/sam_gclk.h"
#include "chip/sam_sercom.h"
#include "sam_sercom.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sercom_coreclk_configure
*
* Description:
* Configure the SERCOM core source clock.
*
* Two generic clocks are used by the SERCOM: GCLK_SERCOMx_CORE and
* GCLK_SERCOM_SLOW. The core clock (GCLK_SERCOMx_CORE) is required to
* clock the SERCOM while operating as a master, while the slow clock
* (GCLK_SERCOM_SLOW) is only required for certain functions. SERCOM
* modules must share the same slow GCLK channel ID.
*
* The baud-rate generator runs off the GCLK_SERCOMx_CORE clock (or,
* optionally, external clock).
*
****************************************************************************/
void sercom_coreclk_configure(int sercom, int gclkgen, bool wrlock)
{
uint16_t regval;
uint8_t glckcore;
/* Set up the SERCOMn_GCLK_ID_CORE clock */
glckcore = (uint8_t)SERCOM_GCLK_ID_CORE(sercom);
regval = ((uint16_t)glckcore << GCLK_CLKCTRL_ID_SHIFT);
/* Select and disable the SERCOMn_GCLK_ID_CORE generic clock */
putreg16(regval, SAM_GCLK_CLKCTRL);
/* Wait for clock to become disabled */
while ((getreg16(SAM_GCLK_CLKCTRL) & GCLK_CLKCTRL_CLKEN) != 0);
/* Select the SERCOMn_GCLK_ID_CORE source clock generator */
regval |= (uint16_t)gclkgen << GCLK_CLKCTRL_GEN_SHIFT;
/* Write the new configuration */
putreg16(regval, SAM_GCLK_CLKCTRL);
/* Enable the SERCOMn_GCLK_ID_CORE generic clock, optionally locking
* further writes to this GCLK.
*/
regval |= GCLK_CLKCTRL_CLKEN;
if (wrlock)
{
regval |= GCLK_CLKCTRL_WRTLOCK;
}
putreg16(regval, SAM_GCLK_CLKCTRL);
}
/****************************************************************************
* Name: sercom_slowclk_configure
*
* Description:
* Configure the SERCOM slow source clock.
*
* Two generic clocks are used by the SERCOM: GCLK_SERCOMx_CORE and
* GCLK_SERCOM_SLOW. The core clock (GCLK_SERCOMx_CORE) is required to
* clock the SERCOM while operating as a master, while the slow clock
* (GCLK_SERCOM_SLOW) is only required for certain functions. SERCOM
* modules must share the same slow GCLK channel ID.
*
****************************************************************************/
void sercom_slowclk_configure(int gclkgen)
{
static bool configured = false;
uint16_t regval;
/* Since GCLK_SERCOM_SLOW is shard amongst all SERCOM modules, it should
* only be configured one time.
*/
if (!configured)
{
/* Set up the SERCOM_GCLK_ID_SLOW clock */
regval = (SERCOM_GCLK_ID_SLOW << GCLK_CLKCTRL_ID_SHIFT);
/* Select and disable the SERCOM_GCLK_ID_SLOW generic clock */
putreg16(regval, SAM_GCLK_CLKCTRL);
/* Wait for clock to become disabled */
while ((getreg16(SAM_GCLK_CLKCTRL) & GCLK_CLKCTRL_CLKEN) != 0);
/* Select the SERCOM_GCLK_ID_SLOW clock source generator */
regval |= (uint16_t)gclkgen << GCLK_CLKCTRL_GEN_SHIFT;
/* Write the new configuration */
putreg16(regval, SAM_GCLK_CLKCTRL);
/* Enable the GCLK_SERCOM_SLOW generic clock and lock further
* writes to this GCLK. When this bit is written, it will lock
* further writes to the generic clock pointed by the CLKCTRL.ID. The
* generic clock generator pointed by CLKCTRL.GEN and the GENDIV.DIV
* will also be locked.
*
* We lock the SERCOM slow clock because it is common to all SERCOM modules
* and, once set, should not be changed again.
*/
regval |= (/* GCLK_CLKCTRL_WRTLOCK | */ GCLK_CLKCTRL_CLKEN);
putreg16(regval, SAM_GCLK_CLKCTRL);
/* Now we are configured */
configured = true;
}
}
