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/****************************************************************************
* configs/vsn/src/sysclock.c
*
* Copyright (C) 2011 Uros Platise. All rights reserved.
*
* Author: Uros Platise <uros.platise@isotel.eu>
*
* 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.
*
****************************************************************************/
/** \file
* \author Uros Platise
* \brief VSN System Clock Configuration
*/
#include "vsn.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/** Selects internal HSI Clock, SYSCLK = 36 MHz, HCLK = 36 MHz
* - HSI at 8 MHz, :2 enters DPLL * 9, to get 36 MHz
* - AHB prescaler is set to 1 for maximum performance of all peripherals and FRAM (18 Mbps)
* - Suitable for start-up and lower power operation
* - Flash Wait State = 1, since it is 64-bit prefetch, it satisfies two 32-bit instructions
* (and branch losses a single cycle only, I found this as the best performance vs. frequency)
* - Sleep with peripherals disabled is about 2.5 mA @ 36 MHz, HSI
*
* \todo:
* - dynamic clock scalling according to cross-peripheral requirements, AHB prescaler could
* change if all other prescalers increase, to maintain the ratio and to have min. HCLK
* possible; This is of interest when peripherals consume 50% of all power, as for instance
* in sleep mode @ 36 MHz, HSI with all peripherals enabled, i = 7 mA, on 24 Mhz 4.8 mA and
* on 16 MHz 3.2 mA only.
*
* \return Nothing, operation is always successful.
*/
void sysclock_select_hsi(void)
{
uint32_t regval;
// Are we running on HSE?
regval = getreg32(STM32_RCC_CR);
if (regval & RCC_CR_HSEON) {
// \todo: check is if we are running on HSE, we need the step down sequenuce from HSE -> HSI
return; // do nothing at this time
}
// Set FLASH prefetch buffer and 1 wait state
regval = getreg32(STM32_FLASH_ACR);
regval &= ~FLASH_ACR_LATENCY_MASK;
regval |= (FLASH_ACR_LATENCY_1|FLASH_ACR_PRTFBE);
putreg32(regval, STM32_FLASH_ACR);
// Set the HCLK source/divider
regval = getreg32(STM32_RCC_CFGR);
regval &= ~RCC_CFGR_HPRE_MASK;
regval |= STM32_RCC_CFGR_HPRE_HSI;
putreg32(regval, STM32_RCC_CFGR);
// Set the PCLK2 divider
regval = getreg32(STM32_RCC_CFGR);
regval &= ~RCC_CFGR_PPRE2_MASK;
regval |= STM32_RCC_CFGR_PPRE2;
putreg32(regval, STM32_RCC_CFGR);
// Set the PCLK1 divider
regval = getreg32(STM32_RCC_CFGR);
regval &= ~RCC_CFGR_PPRE1_MASK;
regval |= STM32_RCC_CFGR_PPRE1;
putreg32(regval, STM32_RCC_CFGR);
// Set the TIM1..8 clock multipliers
#ifdef STM32_TIM27_FREQMUL2
#endif
#ifdef STM32_TIM18_FREQMUL2
#endif
// Set the PLL source = HSI, divider (/2) and multipler (*9)
regval = getreg32(STM32_RCC_CFGR);
regval &= ~(RCC_CFGR_PLLSRC|RCC_CFGR_PLLXTPRE|RCC_CFGR_PLLMUL_MASK);
regval |= (STM32_CFGR_PLLSRC_HSI|STM32_CFGR_PLLMUL_HSI);
putreg32(regval, STM32_RCC_CFGR);
// Enable the PLL
regval = getreg32(STM32_RCC_CR);
regval |= RCC_CR_PLLON;
putreg32(regval, STM32_RCC_CR);
// Wait until the PLL is ready
while ((getreg32(STM32_RCC_CR) & RCC_CR_PLLRDY) == 0);
// Select the system clock source (probably the PLL)
regval = getreg32(STM32_RCC_CFGR);
regval &= ~RCC_CFGR_SW_MASK;
regval |= STM32_SYSCLK_SW;
putreg32(regval, STM32_RCC_CFGR);
// Wait until the selected source is used as the system clock source
while ((getreg32(STM32_RCC_CFGR) & RCC_CFGR_SWS_MASK) != STM32_SYSCLK_SWS);
// map port PD0 and PD1 on OSC pins
regval = getreg32(STM32_AFIO_MAPR);
regval |= AFIO_MAPR_PD01_REMAP;
putreg32(regval, STM32_AFIO_MAPR);
}
/** Selects external HSE Clock, SYSCLK = 72 MHz, HCLK = 36/72 MHz
* - HSE at 9 MHz, DPLL * 8, to get 72 MHz
* - Suitable for maximum performance and USB
* - Sleep power consumption at HSE and at 72 MHz is 5.5 mA (3.1 @ 36 MHz)
* - Option AHB prescaler is set to :2 to be compatible with HSI to remain on HCLK = 36 MHz
* - Flash memory running on 72 MHz needs two wait states
*
* \return Clock selection status
* \retval 0 Successful
* \retval -1 External clock is not provided
* \retval -2 Could not lock to external clock
*/
int sysclock_select_hse(void)
{
uint32_t regval;
// be sure to release PD0 and PD1 pins from the OSC pins
regval = getreg32(STM32_AFIO_MAPR);
regval &= ~AFIO_MAPR_PD01_REMAP;
putreg32(regval, STM32_AFIO_MAPR);
// if (is cc1101 9 MHz clock output enabled), otherwise return with -1
// I think that clock register provides HSE valid signal to detect that as well.
return 0;
}
/****************************************************************************
* Interrupts, Callbacks
****************************************************************************/
/** TODO: Interrupt on lost HSE clock, change it to HSI, ... restarting is
* more complex as the step requires restart of CC1101 device driver;
* so spawn a task for that... once cc1101 is restarted signal an event
* to restart clock.
*/
void sysclock_hse_lost(void)
{
}
/****************************************************************************
* Public Functions
****************************************************************************/
/** Setup system clock, enabled when:
* - CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG
* option is set in .config
*/
void stm32_board_clockconfig(void)
{
sysclock_select_hsi();
}
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