source: rtems/c/src/lib/libbsp/arm/lpc24xx/misc/dma.c @ f90c5fb

/**
 * @file
 *
 * @ingroup lpc24xx
 *
 * @brief DMA support.
 */

/*
 * Copyright (c) 2008, 2009
 * embedded brains GmbH
 * Obere Lagerstr. 30
 * D-82178 Puchheim
 * Germany
 * rtems@embedded-brains.de
 *
 * The license and distribution terms for this file may be found in the file
 * LICENSE in this distribution or at http://www.rtems.com/license/LICENSE.
 */

#include <rtems/endian.h>

#include <bsp/lpc24xx.h>
#include <bsp/dma.h>
#include <bsp/io.h>

/**
 * @brief Table that indicates if a channel is currently occupied.
 */
static bool lpc24xx_dma_channel_occupation [GPDMA_CH_NUMBER];

/**
 * @brief Initializes the general purpose DMA.
 */
void lpc24xx_dma_initialize(void)
{
  rtems_interrupt_level level;

  /* Enable module power */
  lpc24xx_module_enable(LPC24XX_MODULE_GPDMA, 0, LPC24XX_MODULE_PCLK_DEFAULT);

  /* Disable module */
  GPDMA_CONFIG = 0;

  /* Enable module */
  #if BYTE_ORDER == LITTLE_ENDIAN
    GPDMA_CONFIG = GPDMA_CONFIG_EN;
  #else
    GPDMA_CONFIG = GPDMA_CONFIG_EN | GPDMA_CONFIG_MODE;
  #endif

  /* Reset registers */
  GPDMA_SOFT_SREQ = 0;
  GPDMA_SOFT_BREQ = 0;
  GPDMA_SOFT_LSREQ = 0;
  GPDMA_SOFT_LBREQ = 0;
  GPDMA_SYNC = 0;
}

/**
 * @brief Tries to obtain the channel @a channel.
 *
 * @retval RTEMS_SUCCESSFUL Successful operation.
 * @retval RTEMS_INVALID_ID Invalid channel number.
 * @retval RTEMS_RESOURCE_IN_USE Channel already occupied.
 */
rtems_status_code lpc24xx_dma_channel_obtain(unsigned channel)
{
  if (channel < GPDMA_CH_NUMBER) {
    rtems_interrupt_level level;
    bool occupation = true;

    rtems_interrupt_disable(level);
    occupation = lpc24xx_dma_channel_occupation [channel];
    lpc24xx_dma_channel_occupation [channel] = true;
    rtems_interrupt_enable(level);

    return occupation ? RTEMS_RESOURCE_IN_USE : RTEMS_SUCCESSFUL;
  } else {
    return RTEMS_INVALID_ID;
  }
}

/**
 * @brief Releases the channel @a channel.
 *
 * You must have obtained this channel with lpc24xx_dma_channel_obtain()
 * previously.
 *
 * If the channel number @a channel is out of range nothing will happen.
 */
void lpc24xx_dma_channel_release(unsigned channel)
{
  if (channel < GPDMA_CH_NUMBER) {
    lpc24xx_dma_channel_occupation [channel] = false;
  }
}

/**
 * @brief Disables the channel @a channel.
 *
 * If @a force is false the channel will be halted and disabled when the
 * channel is inactive.
 *
 * If the channel number @a channel is out of range the behaviour is undefined.
 */
void lpc24xx_dma_channel_disable(unsigned channel, bool force)
{
  volatile lpc24xx_dma_channel *ch = GPDMA_CH_BASE_ADDR(channel);
  uint32_t cfg = ch->cfg;

  if (!force) {
    /* Halt */
    ch->cfg = SET_FLAG(cfg, GPDMA_CH_CFG_HALT);

    /* Wait for inactive */
    do {
      cfg = ch->cfg;
    } while (IS_FLAG_SET(cfg, GPDMA_CH_CFG_ACTIVE));
  }

  /* Disable */
  ch->cfg = CLEAR_FLAG(cfg, GPDMA_CH_CFG_EN);
}