/*
 * Copyright (C) 2017 Freie Universität Berlin
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License v2.1. See the file LICENSE in the top level
 * directory for more details.
 */

/**
 * @ingroup     cpu_stm32_common
 * @ingroup     drivers_periph_rtt
 * @{
 *
 * @file
 * @brief       RTT implementation using LPTIM1
 *
 * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
 *
 * @}
 */

#include "cpu.h"
#include "irq.h"
#include "periph/rtt.h"

/* this driver is only valid for STM CPUs that provide LPTIMERs */
#if (defined(LPTIM1) && RTT_NUMOF)

/* figure out the used pre-scaler */
#if (RTT_FREQUENCY == 32768)
#define PRE                 (0)
#elif (RTT_FREQUENCY == 16384)
#define PRE                 (LPTIM_CFGR_PRESC_0)
#elif (RTT_FREQUENCY == 8192)
#define PRE                 (LPTIM_CFGR_PRESC_1)
#elif (RTT_FREQUENCY == 4096)
#define PRE                 (LPTIM_CFGR_PRESC_1 | LPTIM_CFGR_PRESC_0)
#elif (RTT_FREQUENCY == 2048)
#define PRE                 (LPTIM_CFGR_PRESC_2)
#elif (RTT_FREQUENCY == 1024)
#define PRE                 (LPTIM_CFGR_PRESC_2 | LPTIM_CFGR_PRESC_0)
#elif (RTT_FREQUENCY == 512)
#define PRE                 (LPTIM_CFGR_PRESC_2 | LPTIM_CFGR_PRESC_1)
#elif (RTT_FREQUENCY == 256)
#define PRE                 (LPTIM_CFGR_PRESC)
#else
#error "RTT config: RTT_FREQUENCY not configured or invalid for your board"
#endif

/* allocate memory for overflow and alarm callbacks + args */
static rtt_cb_t ovf_cb = NULL;
static void *ovf_arg;
static rtt_cb_t to_cb = NULL;
static void *to_arg;

void rtt_init(void)
{
    /* power on the selected LPTIMER */
    rtt_poweron();

    /* stop the timer and reset configuration */
    LPTIM1->CR = 0;

    /* select low speed clock (LSI or LSE) */
    RCC->CCIPR &= ~(RCC_CCIPR_LPTIM1SEL);
#if CLOCK_LSE
    RCC->CCIPR |= (RCC_CCIPR_LPTIM1SEL_1 | RCC_CCIPR_LPTIM1SEL_0);
#else
    RCC->CCIPR |= (RCC_CCIPR_LPTIM1SEL_0);
#endif

    /* set configuration: prescale factor and external clock (LSI or LSE) */
    LPTIM1->CFGR = PRE;
    /* enable overflow and compare interrupts */
    LPTIM1->IER = (LPTIM_IER_ARRMIE | LPTIM_IER_CMPMIE);
    NVIC_EnableIRQ(LPTIM1_IRQn);
    /* enable timer */
    LPTIM1->CR = LPTIM_CR_ENABLE;
    /* set auto-reload value (timer needs to be enabled for this) */
    LPTIM1->ARR = RTT_MAX_VALUE;
    /* start the timer */
    LPTIM1->CR |= LPTIM_CR_CNTSTRT;
}

uint32_t rtt_get_counter(void)
{
    return (uint32_t)LPTIM1->CNT;
}

void rtt_set_overflow_cb(rtt_cb_t cb, void *arg)
{
    assert(cb);

    unsigned is = irq_disable();
    ovf_cb  = cb;
    ovf_arg = arg;
    irq_restore(is);
}

void rtt_clear_overflow_cb(void)
{
    ovf_cb = NULL;
}

void rtt_set_alarm(uint32_t alarm, rtt_cb_t cb, void *arg)
{
    assert(cb && !(alarm & ~RTT_MAX_VALUE));

    unsigned is = irq_disable();
    to_cb  = cb;
    to_arg = arg;
    LPTIM1->CMP = (uint16_t)alarm;
    irq_restore(is);
}

void rtt_clear_alarm(void)
{
    to_cb = NULL;
}

void rtt_poweron(void)
{
#ifdef RCC_APB1ENR1_LPTIM1EN
    periph_clk_en(APB1, RCC_APB1ENR1_LPTIM1EN);
#else
    periph_clk_en(APB1, RCC_APB1ENR_LPTIM1EN);
#endif
}

void rtt_poweroff(void)
{
#ifdef RCC_APB1ENR1_LPTIM1EN
    periph_clk_dis(APB1, RCC_APB1ENR1_LPTIM1EN);
#else
    periph_clk_dis(APB1, RCC_APB1ENR_LPTIM1EN);
#endif
}

void isr_lptim1(void)
{
    if (LPTIM1->ISR & LPTIM_ISR_CMPM) {
        if (to_cb) {
            /* 'consume' the callback (as it might be set again in the cb) */
            rtt_cb_t tmp = to_cb;
            to_cb = NULL;
            tmp(to_arg);
        }
    }
    if (LPTIM1->ISR & LPTIM_ISR_ARRM) {
        if (ovf_cb) {
            ovf_cb(ovf_arg);
        }
    }
    LPTIM1->ICR = (LPTIM_ICR_ARRMCF | LPTIM_ICR_CMPMCF);

    cortexm_isr_end();
}

#endif /* LPTIM1 */