File content as of revision 149:156823d33999:

/* mbed Microcontroller Library
 * Copyright (c) 2015 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "mbed_assert.h"
#include "spi_api.h"

#include <math.h>

#include "cmsis.h"
#include "pinmap.h"
#include "clk_freqs.h"
#include "PeripheralPins.h"

void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel) {
    // determine the SPI to use
    SPIName spi_mosi = (SPIName)pinmap_peripheral(mosi, PinMap_SPI_MOSI);
    SPIName spi_miso = (SPIName)pinmap_peripheral(miso, PinMap_SPI_MISO);
    SPIName spi_sclk = (SPIName)pinmap_peripheral(sclk, PinMap_SPI_SCLK);
    SPIName spi_ssel = (SPIName)pinmap_peripheral(ssel, PinMap_SPI_SSEL);
    SPIName spi_data = (SPIName)pinmap_merge(spi_mosi, spi_miso);
    SPIName spi_cntl = (SPIName)pinmap_merge(spi_sclk, spi_ssel);
    
    obj->spi = (SPI_Type*)pinmap_merge(spi_data, spi_cntl);
    MBED_ASSERT((int)obj->spi != NC);

    SIM->SCGC5 |= SIM_SCGC5_PORTC_MASK | SIM_SCGC5_PORTD_MASK;
    SIM->SCGC6 |= SIM_SCGC6_SPI0_MASK;

    obj->spi->MCR &= ~(SPI_MCR_MDIS_MASK | SPI_MCR_HALT_MASK);
    //obj->spi->MCR |= SPI_MCR_DIS_RXF_MASK | SPI_MCR_DIS_TXF_MASK;

    // not halt in the debug mode
    obj->spi->SR |= SPI_SR_EOQF_MASK;

    // pin out the spi pins
    pinmap_pinout(mosi, PinMap_SPI_MOSI);
    pinmap_pinout(miso, PinMap_SPI_MISO);
    pinmap_pinout(sclk, PinMap_SPI_SCLK);
    if (ssel != NC) {
        pinmap_pinout(ssel, PinMap_SPI_SSEL);
    }
}

void spi_free(spi_t *obj) {
    // [TODO]
}
void spi_format(spi_t *obj, int bits, int mode, int slave) {
    MBED_ASSERT((bits > 4) || (bits < 16));
    MBED_ASSERT((mode >= 0) && (mode <= 3));

    uint8_t polarity = (mode & 0x2) ? 1 : 0;
    uint8_t phase = (mode & 0x1) ? 1 : 0;
    uint8_t old_polarity = (obj->spi->CTAR[0] & SPI_CTAR_CPOL_MASK) != 0;

    // set master/slave
    if (slave) {
        obj->spi->MCR &= ~SPI_MCR_MSTR_MASK;
    } else {
        obj->spi->MCR |= (1UL << SPI_MCR_MSTR_SHIFT);
    }

    // CTAR0 is used
    obj->spi->CTAR[0] &= ~(SPI_CTAR_CPHA_MASK | SPI_CTAR_CPOL_MASK | SPI_CTAR_FMSZ_MASK);
    obj->spi->CTAR[0] |= (polarity << SPI_CTAR_CPOL_SHIFT) | (phase << SPI_CTAR_CPHA_SHIFT) | ((bits - 1) << SPI_CTAR_FMSZ_SHIFT);
    
    //If clk idle state was changed, start a dummy transmission
    //This is a 'feature' in DSPI: https://community.freescale.com/thread/105526
    if ((old_polarity != polarity) && (slave == 0)) {
        //Start transfer (CS should be high, so shouldn't matter)
        spi_master_write(obj, 0xFFFF);
    }
}

static const uint8_t baudrate_prescaler[] = {2,3,5,7};
static const uint16_t baudrate_scaler[] = {2,4,6,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768};

void spi_frequency(spi_t *obj, int hz) {
    uint32_t f_error = 0;
    uint32_t p_error = 0xffffffff;
    uint32_t ref = 0;
    uint32_t br = 0;
    uint32_t ref_spr = 0;
    uint32_t ref_prescaler = 0;
    uint32_t ref_dr = 0;

    // bus clk
    uint32_t PCLK = bus_frequency();

    for (uint32_t i = 0; i < 4; i++) {
        for (br = 0; br <= 15; br++) {
            for (uint32_t dr = 0; dr < 2; dr++) {
                ref = (PCLK * (1U + dr) / baudrate_prescaler[i]) / baudrate_scaler[br];
                if (ref > (uint32_t)hz)
                    continue;
                f_error = hz - ref;
                if (f_error < p_error) {
                    ref_spr = br;
                    ref_prescaler = i;
                    ref_dr = dr;
                    p_error = f_error;
                }
            }
        }
    }

    // set PBR and BR
    obj->spi->CTAR[0] &= ~(SPI_CTAR_PBR_MASK | SPI_CTAR_BR_MASK | SPI_CTAR_DBR_MASK);
    obj->spi->CTAR[0] |= (ref_prescaler << SPI_CTAR_PBR_SHIFT) | (ref_spr << SPI_CTAR_BR_SHIFT) | (ref_dr << SPI_CTAR_DBR_SHIFT);
}

static inline int spi_writeable(spi_t *obj) {
    return (obj->spi->SR & SPI_SR_TFFF_MASK) ? 1 : 0;
}

static inline int spi_readable(spi_t *obj) {
    return (obj->spi->SR & SPI_SR_RFDF_MASK) ? 1 : 0;
}

int spi_master_write(spi_t *obj, int value) {
    //clear RX buffer flag
    obj->spi->SR |= SPI_SR_RFDF_MASK;
    // wait tx buffer empty
    while(!spi_writeable(obj));
    obj->spi->PUSHR = SPI_PUSHR_TXDATA(value & 0xffff) /*| SPI_PUSHR_EOQ_MASK*/;

    // wait rx buffer full
    while (!spi_readable(obj));
    return obj->spi->POPR;
}

int spi_slave_receive(spi_t *obj) {
    return spi_readable(obj);
}

int spi_slave_read(spi_t *obj) {
    obj->spi->SR |= SPI_SR_RFDF_MASK;
    return obj->spi->POPR;
}

void spi_slave_write(spi_t *obj, int value) {
    while (!spi_writeable(obj));
}