nuttx/drivers/serial/serial_dma.c

/************************************************************************************
 * drivers/serial/serial_dma.c
 *
 *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
 *   Author:  Max Neklyudov <macscomp@gmail.com>
 *
 * 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.
 *
 ************************************************************************************/

/************************************************************************************
 * Included Files
 ************************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <semaphore.h>
#include <debug.h>

#include <nuttx/serial/serial.h>

#ifdef CONFIG_SERIAL_DMA

/************************************************************************************
 * Public Functions
 ************************************************************************************/

/************************************************************************************
 * Name: uart_xmitchars_dma
 *
 * Description:
 *   Set up to transfer bytes from the TX circular buffer using DMA
 *
 ************************************************************************************/

void uart_xmitchars_dma(FAR uart_dev_t *dev)
{
  FAR struct uart_dmaxfer_s *xfer = &dev->dmatx;

  if (dev->xmit.head == dev->xmit.tail)
    {
      /* No data to transfer. */

      return;
    }

  if (dev->xmit.tail < dev->xmit.head)
    {
      xfer->buffer  = &dev->xmit.buffer[dev->xmit.tail];
      xfer->length  = dev->xmit.head - dev->xmit.tail;
      xfer->nbuffer = NULL;
      xfer->nlength = 0;
    }
  else
    {
      xfer->buffer  = &dev->xmit.buffer[dev->xmit.tail];
      xfer->length  = dev->xmit.size - dev->xmit.tail;
      xfer->nbuffer = dev->xmit.buffer;
      xfer->nlength = dev->xmit.head;
    }

  uart_dmasend(dev);
}

/************************************************************************************
 * Name: uart_xmitchars_done
 *
 * Description:
 *   Perform operations necessary at the complete of DMA including adjusting the
 *   TX circular buffer indices and waking up of any threads that may have been
 *   waiting for space to become available in the TX circular buffer.
 *
 ************************************************************************************/

void uart_xmitchars_done(FAR uart_dev_t *dev)
{
  FAR struct uart_dmaxfer_s *xfer = &dev->dmatx;
  size_t nbytes = xfer->nbytes;
  struct uart_buffer_s *txbuf = &dev->xmit;

  /* Move tail for nbytes. */

  txbuf->tail  = (txbuf->tail + nbytes) % txbuf->size;
  xfer->nbytes = 0;
  xfer->length = xfer->nlength = 0;

  /* If any bytes were removed from the buffer, inform any waiters there there is
   * space available.
   */

  if (nbytes)
    {
      uart_datasent(dev);
    }
}

/************************************************************************************
 * Name: uart_recvchars_dma
 *
 * Description:
 *   Set up to receive bytes into the RX circular buffer using DMA
 *
 ************************************************************************************/

void uart_recvchars_dma(FAR uart_dev_t *dev)
{
  FAR struct uart_dmaxfer_s *xfer = &dev->dmarx;
  FAR struct uart_buffer_s *rxbuf = &dev->recv;
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
  unsigned int nbuffered;
  unsigned int watermark;
#endif
  bool is_full;
  int nexthead = rxbuf->head + 1;

  if (nexthead >= rxbuf->size)
    {
      nexthead = 0;
    }

  is_full = nexthead == rxbuf->tail;

#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
  /* Pre-calcuate the watermark level that we will need to test against. */

  watermark = (CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK * rxbuf->size) / 100;
#endif

#ifdef CONFIG_SERIAL_IFLOWCONTROL
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
  /* How many bytes are buffered */

  if (rxbuf->head >= rxbuf->tail)
    {
      nbuffered = rxbuf->head - rxbuf->tail;
    }
  else
    {
      nbuffered = rxbuf->size - rxbuf->tail + rxbuf->head;
    }

  /* Is the level now above the watermark level that we need to report? */

  if (nbuffered >= watermark)
    {
      /* Let the lower level driver know that the watermark level has been
       * crossed.  It will probably activate RX flow control.
       */

      if (uart_rxflowcontrol(dev, nbuffered, true))
        {
          /* Low-level driver activated RX flow control, return now. */

          return;
        }
    }

#else
  /* Check if RX buffer is full and allow serial low-level driver to pause
   * processing. This allows proper utilization of hardware flow control.
   */

  if (is_full)
    {
      if (uart_rxflowcontrol(dev, rxbuf->size, true))
        {
          /* Low-level driver activated RX flow control, return now. */

          return;
        }
    }
#endif
#endif

  if (is_full)
    {
      /* If there is no free space in receive buffer we cannot start DMA
       * transfer.
       */

      return;
    }

  if (rxbuf->tail <= rxbuf->head)
    {
      xfer->buffer  = &rxbuf->buffer[rxbuf->head];
      xfer->nbuffer = rxbuf->buffer;

      if (rxbuf->tail > 0)
        {
          xfer->length  = rxbuf->size - rxbuf->head;
          xfer->nlength = rxbuf->tail - 1;
        }
      else
        {
          xfer->length  = rxbuf->size - rxbuf->head - 1;
          xfer->nlength = 0;
        }
    }
  else
    {
      xfer->buffer  = &rxbuf->buffer[rxbuf->head];
      xfer->length  = rxbuf->tail - rxbuf->head - 1;
      xfer->nbuffer = NULL;
      xfer->nlength = 0;
    }

  uart_dmareceive(dev);
}

/************************************************************************************
 * Name: uart_recvchars_done
 *
 * Description:
 *   Perform operations necessary at the complete of DMA including adjusting the
 *   RX circular buffer indices and waking up of any threads that may have been
 *   waiting for new data to become available in the RX circular buffer.
 *
 ************************************************************************************/

void uart_recvchars_done(FAR uart_dev_t *dev)
{
  FAR struct uart_dmaxfer_s *xfer = &dev->dmarx;
  FAR struct uart_buffer_s *rxbuf = &dev->recv;
  size_t nbytes = xfer->nbytes;

  /* Move head for nbytes. */

  rxbuf->head  = (rxbuf->head + nbytes) % rxbuf->size;
  xfer->nbytes = 0;
  xfer->length = xfer->nlength = 0;

  /* If any bytes were added to the buffer, inform any waiters there is new
   * incoming data available.
   */

  if (nbytes)
    {
      uart_datareceived(dev);
    }
}

#endif /* CONFIG_SERIAL_DMA */