2.3-InternetRadio/nutos/nut/arch/arm/dev/atmel/spibus_at91ssc.c

/*
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/*!
 * \file arch/arm/dev/atmel/spibus_at91ssc.c
 * \brief General SSC SPI bus driver routines.
 *
 * \verbatim
 * $Id$
 * \endverbatim
 */

#include <dev/spibus_ssc.h>
#include <sys/timer.h>

/*!
 * \brief Update SPI settings.
 */
int SscSpiSetup(NUTSPINODE * node)
{
    uint32_t mck;
    AT91SSCREG *sscreg = (AT91SSCREG *) node->node_stat;

    /* The SSC can transfer 8, 16 or 32 bits only. */
    if (node->node_bits != 8 && node->node_bits != 16 && node->node_bits != 32) {
        return -1;
    }
    sscreg->at91ssc_fmr = ((node->node_bits - 1) << SSC_DATLEN_LSB) | SSC_MSBF;

    /* Query peripheral clock. */
    mck = NutClockGet(NUT_HWCLK_PERIPHERAL);
    /* Calculate the SPI clock divider: n=mck/(2*rate). Avoid rounding errors. */
    sscreg->at91ssc_cmr = mck + node->node_rate - 1;
    sscreg->at91ssc_cmr /= node->node_rate;
    sscreg->at91ssc_cmr /= 2;
    /* Honor minimum and maximum value. */
    if (sscreg->at91ssc_cmr < 3) {
        /* Theoretically 1, but any value below 3 fails on the EIR.
           No other boards tested so far. */
        sscreg->at91ssc_cmr = 3;
    }
    else if (sscreg->at91ssc_cmr > 4095) {
        /* SSC maximum divider on the SAM7SE. No other CPUs had been tested. */
        sscreg->at91ssc_cmr = 4095;
    }
    /* Calculate the actual rate. */
    node->node_rate = mck / sscreg->at91ssc_cmr / 2;

    /* Update done. */
    node->node_mode &= ~SPI_MODE_UPDATE;

    return 0;
}