Implement high level DMA infrastructure for serial devices

ChangeLog

@@ -11084,4 +11084,7 @@
 	* drivers/mtd/mtd_progmem.c:  Add an upper half MTD device that can
 	  use the interfaces defined in included/nuttx/progmem.h to provide
 	  a standard MTD interface (2015-11-12).
+	* drivers/serial/serial.c, serialirq.c and include/nuttx/serial/serial.h:
+	  Implement high level DMA infrastructure for serial devices.  From
+	  Max Neklyudov (2015-11-12).
 

configs

@@ -1 +1 @@
-Subproject commit 758aa6d23647d98fb1a6064175a8abd6c9cc28b2
+Subproject commit 4d23ce39bf6bbf3ca0161ff6247fc9fe1610890f

drivers/serial/Kconfig

@@ -540,6 +540,10 @@ config SERIAL_OFLOWCONTROL
 	bool
 	default n
 
+config SERIAL_DMA
+	bool
+	default n
+
 config SERIAL_IFLOWCONTROL_WATERMARKS
 	bool "RX flow control watermarks"
 	default n
@@ -762,6 +766,13 @@ config UART_OFLOWCONTROL
 	---help---
 		Enable UART CTS flow control
 
+config UART_DMA
+	bool "UART DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART
+
 endmenu
 
 menu "UART0 Configuration"
@@ -820,6 +831,13 @@ config UART0_OFLOWCONTROL
 	---help---
 		Enable UART0 CTS flow control
 
+config UART0_DMA
+	bool "UART0 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART0
+
 endmenu
 
 menu "USART0 Configuration"
@@ -878,6 +896,13 @@ config USART0_OFLOWCONTROL
 	---help---
 		Enable USART0 CTS flow control
 
+config USART0_DMA
+	bool "USART0 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART0
+
 endmenu
 
 menu "UART1 Configuration"
@@ -936,6 +961,13 @@ config UART1_OFLOWCONTROL
 	---help---
 		Enable UART1 CTS flow control
 
+config UART1_DMA
+	bool "UART1 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART1
+
 endmenu
 
 menu "USART1 Configuration"
@@ -994,6 +1026,13 @@ config USART1_OFLOWCONTROL
 	---help---
 		Enable USART1 CTS flow control
 
+config USART1_DMA
+	bool "USART1 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART1
+
 endmenu
 
 menu "UART2 Configuration"
@@ -1052,6 +1091,13 @@ config UART2_OFLOWCONTROL
 	---help---
 		Enable UART2 CTS flow control
 
+config UART2_DMA
+	bool "UART2 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART2
+
 endmenu
 
 menu "USART2 Configuration"
@@ -1110,6 +1156,12 @@ config USART2_OFLOWCONTROL
 	---help---
 		Enable USART2 CTS flow control
 
+config USART2_DMA
+	bool "USART2 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART2
 endmenu
 
 menu "UART3 Configuration"
@@ -1168,6 +1220,13 @@ config UART3_OFLOWCONTROL
 	---help---
 		Enable UART3 CTS flow control
 
+config UART3_DMA
+	bool "UART3 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART3
+
 endmenu
 
 menu "USART3 Configuration"
@@ -1226,6 +1285,13 @@ config USART3_OFLOWCONTROL
 	---help---
 		Enable USART3 CTS flow control
 
+config USART3_DMA
+	bool "USART3 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART3
+
 endmenu
 
 menu "UART4 Configuration"
@@ -1284,6 +1350,13 @@ config UART4_OFLOWCONTROL
 	---help---
 		Enable UART4 CTS flow control
 
+config UART4_DMA
+	bool "UART4 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART4
+
 endmenu
 
 menu "USART4 Configuration"
@@ -1342,6 +1415,13 @@ config USART4_OFLOWCONTROL
 	---help---
 		Enable USART4 CTS flow control
 
+config USART4_DMA
+	bool "USART4 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART4
+
 endmenu
 
 menu "UART5 Configuration"
@@ -1400,6 +1480,13 @@ config UART5_OFLOWCONTROL
 	---help---
 		Enable UART5 CTS flow control
 
+config UART5_DMA
+	bool "UART5 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART5
+
 endmenu
 
 menu "USART5 Configuration"
@@ -1458,6 +1545,13 @@ config USART5_OFLOWCONTROL
 	---help---
 		Enable USART5 CTS flow control
 
+config USART5_DMA
+	bool "USART5 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART5
+
 endmenu
 
 menu "USART6 Configuration"
@@ -1516,6 +1610,13 @@ config USART6_OFLOWCONTROL
 	---help---
 		Enable USART6 CTS flow control
 
+config USART6_DMA
+	bool "USART6 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART6
+
 endmenu
 
 menu "UART6 Configuration"
@@ -1574,6 +1675,13 @@ config UART6_OFLOWCONTROL
 	---help---
 		Enable UART6 CTS flow control
 
+config UART6_DMA
+	bool "UART6 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART6
+
 endmenu
 
 menu "USART7 Configuration"
@@ -1632,6 +1740,13 @@ config USART7_OFLOWCONTROL
 	---help---
 		Enable USART7 CTS flow control
 
+config USART7_DMA
+	bool "USART7 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART7
+
 endmenu
 
 menu "UART7 Configuration"
@@ -1690,6 +1805,13 @@ config UART7_OFLOWCONTROL
 	---help---
 		Enable UART7 CTS flow control
 
+config UART7_DMA
+	bool "UART7 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART7
+
 endmenu
 
 menu "USART8 Configuration"
@@ -1748,6 +1870,13 @@ config USART8_OFLOWCONTROL
 	---help---
 		Enable USART8 CTS flow control
 
+config USART8_DMA
+	bool "USART8 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART8
+
 endmenu
 
 menu "UART8 Configuration"
@@ -1806,6 +1935,13 @@ config UART8_OFLOWCONTROL
 	---help---
 		Enable UART8 CTS flow control
 
+config UART8_DMA
+	bool "UART8 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on UART8
+
 endmenu
 
 menu "SCI0 Configuration"

drivers/serial/serial.c

@@ -249,6 +249,9 @@ static int uart_putxmitchar(FAR uart_dev_t *dev, int ch, bool oktoblock)
                */
 
               dev->xmitwaiting = true;
+#ifdef CONFIG_SERIAL_DMA
+              uart_dmatxavail(dev);
+#endif
               uart_enabletxint(dev);
               ret = uart_takesem(&dev->xmitsem, true);
               uart_disabletxint(dev);
@@ -507,6 +510,9 @@ static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer,
 
   if (dev->xmit.head != dev->xmit.tail)
     {
+#ifdef CONFIG_SERIAL_DMA
+      uart_dmatxavail(dev);
+#endif
       uart_enabletxint(dev);
     }
 
@@ -707,6 +713,20 @@ static ssize_t uart_read(FAR struct file *filep, FAR char *buffer, size_t buflen
                */
 
               flags = irqsave();
+
+#ifdef CONFIG_SERIAL_DMA
+              /* If RX buffer is empty move tail and head to zero position */
+
+              if (rxbuf->head == rxbuf->tail)
+                {
+                  rxbuf->head = rxbuf->tail = 0;
+                }
+
+              /* Notify DMA that there is free space in the RX buffer */
+
+              uart_dmarxfree(dev);
+#endif
+
               uart_enablerxint(dev);
 
 #ifdef CONFIG_SERIAL_REMOVABLE
@@ -778,6 +798,27 @@ static ssize_t uart_read(FAR struct file *filep, FAR char *buffer, size_t buflen
         }
     }
 
+#ifdef CONFIG_SERIAL_DMA
+  flags = irqsave();
+
+  /* If RX buffer is empty move tail and head to zero position */
+
+  if (rxbuf->head == rxbuf->tail)
+    {
+      rxbuf->head = rxbuf->tail = 0;
+    }
+
+  irqrestore(flags);
+
+  /* Notify DMA that there is free space in the RX buffer */
+
+  uart_dmarxfree(dev);
+
+  /* RX interrupt could be disabled by RX buffer overflow. Enable it now. */
+
+  uart_enablerxint(dev);
+#endif
+
 #ifdef CONFIG_SERIAL_IFLOWCONTROL
 #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
   /* How many bytes are now buffered */
@@ -1281,6 +1322,12 @@ static int uart_open(FAR struct file *filep)
         }
 #endif
 
+#ifdef CONFIG_SERIAL_DMA
+      /* Notify DMA that there is free space in the RX buffer */
+
+      uart_dmarxfree(dev);
+#endif
+
       /* Enable the RX interrupt */
 
       uart_enablerxint(dev);

drivers/serial/serialirq.c

@@ -1,7 +1,7 @@
 /************************************************************************************
  * drivers/serial/serialirq.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -65,10 +65,269 @@
  * Private Functions
  ************************************************************************************/
 
+/************************************************************************************
+ * Name: uart_dorxflowcontrol
+ *
+ * Description:
+ *   Handle RX flow control using watermark levels or not
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SERIAL_IFLOWCONTROL
+#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
+static inline bool uart_dorxflowcontrol(FAR uart_dev_t *dev,
+                                        FAR struct uart_buffer_s *rxbuf,
+                                        unsigned int watermark)
+{
+  unsigned int nbuffered;
+
+  /* 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, exit loop now. */
+
+          return true;
+        }
+    }
+
+  return false;
+}
+#else
+static inline bool uart_dorxflowcontrol(FAR uart_dev_t *dev,
+                                        FAR struct uart_buffer_s *rxbuf,
+                                        bool is_full)
+{
+  /* 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, exit loop now. */
+
+          return true;
+        }
+    }
+
+  return false;
+}
+#endif
+#endif
+
 /************************************************************************************
  * Public Functions
  ************************************************************************************/
 
+/************************************************************************************
+ * Name: uart_xmitchars_dma
+ *
+ * Description:
+ *   Set up to transfer bytes from the TX circular buffer using DMA
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SERIAL_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);
+}
+#endif /* CONFIG_SERIAL_DMA */
+
+/************************************************************************************
+ * 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_DMA
+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);
+    }
+}
+#endif /* CONFIG_SERIAL_DMA */
+
+/************************************************************************************
+ * Name: uart_recvchars_dma
+ *
+ * Description:
+ *   Set up to receive bytes into the RX circular buffer using DMA
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SERIAL_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 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
+  if (uart_dorxflowcontrol(dev, rxbuf, watermark))
+    {
+      return;
+    }
+#else
+  if (uart_dorxflowcontrol(dev, rxbuf, is_full))
+    {
+      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 /* CONFIG_SERIAL_DMA */
+
+/************************************************************************************
+ * 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_DMA
+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 */
+
 /************************************************************************************
  * Name: uart_xmitchars
  *
@@ -145,6 +404,7 @@ void uart_recvchars(FAR uart_dev_t *dev)
   unsigned int status;
   int nexthead = rxbuf->head + 1;
   uint16_t nbytes = 0;
+  bool is_full;
 
   if (nexthead >= rxbuf->size)
     {
@@ -163,52 +423,19 @@ void uart_recvchars(FAR uart_dev_t *dev)
 
   while (uart_rxavailable(dev))
     {
-      bool is_full = (nexthead == rxbuf->tail);
+      is_full = (nexthead == rxbuf->tail);
       char ch;
 
 #ifdef CONFIG_SERIAL_IFLOWCONTROL
 #ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
-      unsigned int nbuffered;
+      if (uart_dorxflowcontrol(dev, rxbuf, watermark))
-
-      /* How many bytes are buffered */
-
-      if (rxbuf->head >= rxbuf->tail)
         {
-          nbuffered = rxbuf->head - rxbuf->tail;
+          break;
-        }
-      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, exit loop now. */
-
-              break;
-            }
         }
 #else
-      /* Check if RX buffer is full and allow serial low-level driver to pause
+      if (uart_dorxflowcontrol(dev, rxbuf, is_full))
-       * processing. This allows proper utilization of hardware flow control.
-       */
-
-      if (is_full)
         {
-          if (uart_rxflowcontrol(dev, rxbuf->size, true))
+          break;
-            {
-              /* Low-level driver activated RX flow control, exit loop now. */
-
-              break;
-            }
         }
 #endif
 #endif
@@ -240,7 +467,7 @@ void uart_recvchars(FAR uart_dev_t *dev)
         }
     }
 
-  /* If any bytes were added to the buffer, inform any waiters there there is new
+  /* If any bytes were added to the buffer, inform any waiters there is new
    * incoming data available.
    */
 

include/nuttx/serial/serial.h

@@ -1,7 +1,7 @@
 /************************************************************************************
  * include/nuttx/serial/serial.h
  *
- *   Copyright (C) 2007-2008, 2012-2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2008, 2012-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -104,9 +104,16 @@
 #define uart_send(dev,ch)        dev->ops->send(dev,ch)
 #define uart_receive(dev,s)      dev->ops->receive(dev,s)
 
+#ifdef CONFIG_SERIAL_DMA
+#  define uart_dmasend(dev)      dev->ops->dmasend(dev)
+#  define uart_dmareceive(dev)   dev->ops->dmareceive(dev)
+#  define uart_dmarxfree(dev)    dev->ops->dmarxfree(dev)
+#  define uart_dmatxavail(dev)   dev->ops->dmatxavail(dev)
+#endif
+
 #ifdef CONFIG_SERIAL_IFLOWCONTROL
-#define uart_rxflowcontrol(dev,n,u) \
+#  define uart_rxflowcontrol(dev,n,u) \
-  (dev->ops->rxflowcontrol && dev->ops->rxflowcontrol(dev,n,u))
+    (dev->ops->rxflowcontrol && dev->ops->rxflowcontrol(dev,n,u))
 #endif
 
 /************************************************************************************
@@ -127,6 +134,17 @@ struct uart_buffer_s
   FAR char        *buffer; /* Pointer to the allocated buffer memory */
 };
 
+#ifdef CONFIG_SERIAL_DMA
+struct uart_dmaxfer_s
+{
+  FAR char        *buffer;  /* First DMA buffer */
+  FAR char        *nbuffer; /* Next DMA buffer */
+  size_t           length;  /* Length of first DMA buffer */
+  size_t           nlength; /* Length of next DMA buffer */
+  size_t           nbytes;  /* Bytes actually transferred by DMA from both buffers */
+};
+#endif /* CONFIG_SERIAL_DMA */
+
 /* This structure defines all of the operations providd by the architecture specific
  * logic.  All fields must be provided with non-NULL function pointers by the
  * caller of uart_register().
@@ -199,6 +217,24 @@ struct uart_ops_s
                              unsigned int nbuffered, bool upper);
 #endif
 
+#ifdef CONFIG_SERIAL_DMA
+  /* Start transfer bytes from the TX circular buffer using DMA */
+
+  CODE void (*dmasend)(FAR struct uart_dev_s *dev);
+
+  /* Start transfer bytes from the TX circular buffer using DMA */
+
+  CODE void (*dmareceive)(FAR struct uart_dev_s *dev);
+
+  /* Notify DMA that there is free space in the RX buffer */
+
+  CODE void (*dmarxfree)(FAR struct uart_dev_s *dev);
+
+  /* Notify DMA that there is data to be transferred in the TX buffer */
+
+  CODE void (*dmatxavail)(FAR struct uart_dev_s *dev);
+#endif
+
   /* This method will send one byte on the UART */
 
   CODE void (*send)(FAR struct uart_dev_s *dev, int ch);
@@ -266,6 +302,14 @@ struct uart_dev_s
   struct uart_buffer_s xmit;         /* Describes transmit buffer */
   struct uart_buffer_s recv;         /* Describes receive buffer */
 
+#ifdef CONFIG_SERIAL_DMA
+
+  /* DMA transfers */
+
+  struct uart_dmaxfer_s dmatx;       /* Describes transmit DMA transfer */
+  struct uart_dmaxfer_s dmarx;       /* Describes receive DMA transfer */
+#endif
+
   /* Driver interface */
 
   FAR const struct uart_ops_s *ops;  /* Arch-specific operations */
@@ -385,6 +429,58 @@ void uart_datasent(FAR uart_dev_t *dev);
 void uart_connected(FAR uart_dev_t *dev, bool connected);
 #endif
 
+/************************************************************************************
+ * Name: uart_xmitchars_dma
+ *
+ * Description:
+ *   Set up to transfer bytes from the TX circular buffer using DMA
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SERIAL_DMA
+void uart_xmitchars_dma(FAR uart_dev_t *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_DMA
+void uart_xmitchars_done(FAR uart_dev_t *dev);
+#endif
+
+/************************************************************************************
+ * Name: uart_recvchars_dma
+ *
+ * Description:
+ *   Set up to receive bytes into the RX circular buffer using DMA
+ *
+ ************************************************************************************/
+
+#ifdef CONFIG_SERIAL_DMA
+void uart_recvchars_dma(FAR uart_dev_t *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_DMA
+void uart_recvchars_done(FAR uart_dev_t *dev);
+#endif
+
 #undef EXTERN
 #if defined(__cplusplus)
 }