nuttx/drivers/serial/serial_dma.c

/****************************************************************************
 * drivers/serial/serial_dma.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you 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.
 *
 ****************************************************************************/

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

#include <nuttx/config.h>

#include <assert.h>
#include <sys/types.h>
#include <stdint.h>
#include <debug.h>
#include <nuttx/signal.h>

#include <nuttx/serial/serial.h>

#if defined(CONFIG_SERIAL_TXDMA) || defined(CONFIG_SERIAL_RXDMA)

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: uart_recvchars_check_special
 *
 * Description:
 *   Check if the SIGINT character is anywhere in the newly received DMA
 *   buffer.
 *
 *   REVISIT:  We must also remove the SIGINT/SIGTSTP character from the Rx
 *   buffer.  It should not be read as normal data by the caller.
 *
 ****************************************************************************/

#if defined(CONFIG_SERIAL_RXDMA) && \
   (defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGTSTP) || \
    defined(CONFIG_TTY_FORCE_PANIC) || defined(CONFIG_TTY_LAUNCH))
static int uart_recvchars_check_special(FAR uart_dev_t *dev)
{
  FAR struct uart_dmaxfer_s *xfer = &dev->dmarx;
  int signo;

  /* Check if the valid DMAed data is in one or two contiguous regions */

  if (xfer->nbytes <= xfer->length)
    {
      return uart_check_special(dev, xfer->buffer, xfer->nbytes);
    }
  else
    {
      /* REVISIT:  Additional signals could be in the second region. */

      signo = uart_check_special(dev, xfer->buffer, xfer->length);
      if (signo != 0)
        {
          return signo;
        }

      return uart_check_special(dev, xfer->nbuffer,
                                xfer->nbytes - xfer->length);
    }
}
#endif

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

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

#ifdef CONFIG_SERIAL_TXDMA
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);
}
#endif

/****************************************************************************
 * 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.
 *
 ****************************************************************************/

#ifdef CONFIG_SERIAL_TXDMA
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;

  /* Skip the update if the tail position change which mean
   * someone reset (e.g. TCOFLUSH) the xmit buffer during DMA.
   */

  if (xfer->buffer == &txbuf->buffer[txbuf->tail])
    {
      /* Move tail for nbytes. */

      txbuf->tail  = (txbuf->tail + nbytes) % txbuf->size;
    }

  /* Reset xmit buffer. */

  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);
    }
}
#endif

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

#ifdef CONFIG_SERIAL_RXDMA
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;

  /* If RX buffer is empty move tail and head to zero position */

  if (rxbuf->head == rxbuf->tail)
    {
      rxbuf->head = 0;
      rxbuf->tail = 0;
    }

  /* Get the next head index and check if there is room to adding another
   * byte to the buffer.
   */

  nexthead = rxbuf->head + 1;
  if (nexthead >= rxbuf->size)
    {
      nexthead = 0;
    }

  is_full = nexthead == rxbuf->tail;

#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
  /* Pre-calculate 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);
}
#endif

/****************************************************************************
 * 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.
 *
 ****************************************************************************/

#ifdef CONFIG_SERIAL_RXDMA
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;
#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGTSTP) || \
    defined(CONFIG_TTY_FORCE_PANIC) || defined(CONFIG_TTY_LAUNCH)
  int signo = 0;

  /* Check if the SIGINT character is anywhere in the newly received DMA
   * buffer.
   */

  signo = uart_recvchars_check_special(dev);
#endif

  /* 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);
    }

#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGTSTP) || \
    defined(CONFIG_TTY_FORCE_PANIC) || defined(CONFIG_TTY_LAUNCH)
  /* Send the signal if necessary */

  if (signo != 0)
    {
      nxsig_kill(dev->pid, signo);
      uart_reset_sem(dev);
    }
#endif
}
#endif

#endif /* CONFIG_SERIAL_TXDMA || CONFIG_SERIAL_RXDMA */