Removed delay after receiving in recvfrom(). This was killing network performance

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5107 42af7a65-404d-4744-a932-0658087f49c3

28 files changed, 130 insertions, 48 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 9e0ca4b68..5f27953c9 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3274,4 +3274,10 @@
 	* Kconfig: Verify configuration settings for the LPC43xx.  This includes
 	  some corrections to configuration variable names and defconfig settings.
 	* Kconfig: Add and verify configuration settings for the LPC31xx.
-
+	* arch/arm/src/stm32/stm32_uart.h and stm32_serial.c:  Add logic to
+	  re-initialize the console UART as needed to enable DMA on the
+	  console UART (contributed by Mike Smith).
+	* net/recvfrom.c, net/Kconfig, include/nuttx/net/uipopt.h: Remove delay
+	  after receiving data.  That has historical reasons to be there (it
+	  was needed before read-ahead buffering was added), but kills performance.
+	  (Noted by Max Holtzberg).
diff --git a/nuttx/Documentation/NuttxPortingGuide.html b/nuttx/Documentation/NuttxPortingGuide.html
index a03d9810f..b5473549a 100644
--- a/nuttx/Documentation/NuttxPortingGuide.html
+++ b/nuttx/Documentation/NuttxPortingGuide.html
@@ -5037,7 +5037,12 @@ build
     <code>CONFIG_NET_TCP_READAHEAD_BUFSIZE</code>: Size of TCP read-ahead buffers
   </li>
   <li>
-    <code>CONFIG_NET_NTCP_READAHEAD_BUFFERS</code>: Number of TCP read-ahead buffers (may be zero)
+    <code>CONFIG_NET_NTCP_READAHEAD_BUFFERS</code>: Number of TCP read-ahead buffers (may be zero to disable TCP/IP read-ahead buffering)
+  </li>
+  <li>
+    <code>CONFIG_NET_TCP_RECVDELAY</code>: Delay (in deciseconds) after a TCP/IP packet is received.
+     This delay may allow catching of additional packets when TCP/IP read-ahead is disabled.
+     Default: 0
   </li>
   <li>
     <code>CONFIG_NET_MAX_LISTENPORTS</code>: Maximum number of listening TCP ports (all tasks).
diff --git a/nuttx/arch/arm/src/stm32/stm32_uart.h b/nuttx/arch/arm/src/stm32/stm32_uart.h
index 7888d6316..a70923cbf 100644
--- a/nuttx/arch/arm/src/stm32/stm32_uart.h
+++ b/nuttx/arch/arm/src/stm32/stm32_uart.h
@@ -198,11 +198,11 @@
 #  define SERIAL_HAVE_CONSOLE_DMA 1
 #elif defined(CONFIG_USART3_SERIAL_CONSOLE) && defined(CONFIG_USART3_RXDMA)
 #  define SERIAL_HAVE_CONSOLE_DMA 1
-#elif defined(CONFIG_UART4_SERIAL_CONSOLE) && !efined(CONFIG_UART4_RXDMA)
+#elif defined(CONFIG_UART4_SERIAL_CONSOLE) && defined(CONFIG_UART4_RXDMA)
 #  define SERIAL_HAVE_CONSOLE_DMA 1
 #elif defined(CONFIG_UART5_SERIAL_CONSOLE) && defined(CONFIG_UART5_RXDMA)
 #  define SERIAL_HAVE_CONSOLE_DMA 1
-#elif defined(CONFIG_USART6_SERIAL_CONSOLE) && !efined(CONFIG_USART6_RXDMA)
+#elif defined(CONFIG_USART6_SERIAL_CONSOLE) && defined(CONFIG_USART6_RXDMA)
 #  define SERIAL_HAVE_CONSOLE_DMA 1
 #endif
 
diff --git a/nuttx/configs/README.txt b/nuttx/configs/README.txt
index 7ad2825d0..6cd5eef3f 100644
--- a/nuttx/configs/README.txt
+++ b/nuttx/configs/README.txt
@@ -990,7 +990,10 @@ defconfig -- This is a configuration file similar to the Linux
     CONFIG_NET_MAX_LISTENPORTS - Maximum number of listening TCP ports (all tasks)
     CONFIG_NET_TCP_READAHEAD_BUFSIZE - Size of TCP read-ahead buffers
     CONFIG_NET_NTCP_READAHEAD_BUFFERS - Number of TCP read-ahead buffers
-      (may be zero)
+      (may be zero to disable TCP/IP read-ahead buffering)
+    CONFIG_NET_TCP_RECVDELAY - Delay (in deciseconds) after a TCP/IP packet
+      is received.  This delay may allow catching of additional packets
+      when TCP/IP read-ahead is disabled.  Default: 0
     CONFIG_NET_TCPBACKLOG - Incoming connections pend in a backlog until
       accept() is called. The size of the backlog is selected when listen()
       is called.
diff --git a/nuttx/configs/olimex-stm32-p107/nsh/defconfig b/nuttx/configs/olimex-stm32-p107/nsh/defconfig
index 18858d5df..c7c71018a 100644
--- a/nuttx/configs/olimex-stm32-p107/nsh/defconfig
+++ b/nuttx/configs/olimex-stm32-p107/nsh/defconfig
@@ -365,7 +365,7 @@ CONFIG_NET_MULTICAST=n
 #
 # STM32F107vc Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=n
 CONFIG_STM32_RMII=y
 CONFIG_STM32_RMII_MCO=y
diff --git a/nuttx/configs/stm3220g-eval/dhcpd/defconfig b/nuttx/configs/stm3220g-eval/dhcpd/defconfig
index 848121e04..433fe97d2 100644
--- a/nuttx/configs/stm3220g-eval/dhcpd/defconfig
+++ b/nuttx/configs/stm3220g-eval/dhcpd/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/nettest/defconfig b/nuttx/configs/stm3220g-eval/nettest/defconfig
index 7e660ad02..ef5c2da96 100644
--- a/nuttx/configs/stm3220g-eval/nettest/defconfig
+++ b/nuttx/configs/stm3220g-eval/nettest/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/nsh/defconfig b/nuttx/configs/stm3220g-eval/nsh/defconfig
index 48912bd8b..591f24616 100644
--- a/nuttx/configs/stm3220g-eval/nsh/defconfig
+++ b/nuttx/configs/stm3220g-eval/nsh/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/nsh2/defconfig b/nuttx/configs/stm3220g-eval/nsh2/defconfig
index c2ede9c67..03ee777f4 100644
--- a/nuttx/configs/stm3220g-eval/nsh2/defconfig
+++ b/nuttx/configs/stm3220g-eval/nsh2/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/nxwm/defconfig b/nuttx/configs/stm3220g-eval/nxwm/defconfig
index 6e6933325..bd59f47de 100644
--- a/nuttx/configs/stm3220g-eval/nxwm/defconfig
+++ b/nuttx/configs/stm3220g-eval/nxwm/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/ostest/defconfig b/nuttx/configs/stm3220g-eval/ostest/defconfig
index d0ace11bc..30ec69419 100644
--- a/nuttx/configs/stm3220g-eval/ostest/defconfig
+++ b/nuttx/configs/stm3220g-eval/ostest/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3220g-eval/telnetd/defconfig b/nuttx/configs/stm3220g-eval/telnetd/defconfig
index 2ff215afc..550f654ba 100644
--- a/nuttx/configs/stm3220g-eval/telnetd/defconfig
+++ b/nuttx/configs/stm3220g-eval/telnetd/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F20xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/dhcpd/defconfig b/nuttx/configs/stm3240g-eval/dhcpd/defconfig
index 382ce6155..4e22244bb 100644
--- a/nuttx/configs/stm3240g-eval/dhcpd/defconfig
+++ b/nuttx/configs/stm3240g-eval/dhcpd/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/nettest/defconfig b/nuttx/configs/stm3240g-eval/nettest/defconfig
index 9eb8f3d5c..e21c1070b 100644
--- a/nuttx/configs/stm3240g-eval/nettest/defconfig
+++ b/nuttx/configs/stm3240g-eval/nettest/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/nsh/defconfig b/nuttx/configs/stm3240g-eval/nsh/defconfig
index 8b2617ec0..34f84db07 100644
--- a/nuttx/configs/stm3240g-eval/nsh/defconfig
+++ b/nuttx/configs/stm3240g-eval/nsh/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/nsh2/defconfig b/nuttx/configs/stm3240g-eval/nsh2/defconfig
index 00d9dac0a..dfb837e8a 100644
--- a/nuttx/configs/stm3240g-eval/nsh2/defconfig
+++ b/nuttx/configs/stm3240g-eval/nsh2/defconfig
@@ -204,7 +204,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/nxconsole/defconfig b/nuttx/configs/stm3240g-eval/nxconsole/defconfig
index 172d17b6f..417201f3e 100644
--- a/nuttx/configs/stm3240g-eval/nxconsole/defconfig
+++ b/nuttx/configs/stm3240g-eval/nxconsole/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/nxwm/defconfig b/nuttx/configs/stm3240g-eval/nxwm/defconfig
index 07bc408dc..88d3ecb8d 100644
--- a/nuttx/configs/stm3240g-eval/nxwm/defconfig
+++ b/nuttx/configs/stm3240g-eval/nxwm/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/ostest/defconfig b/nuttx/configs/stm3240g-eval/ostest/defconfig
index 1f2304730..2b95735bb 100644
--- a/nuttx/configs/stm3240g-eval/ostest/defconfig
+++ b/nuttx/configs/stm3240g-eval/ostest/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/telnetd/defconfig b/nuttx/configs/stm3240g-eval/telnetd/defconfig
index 44a0f27ba..9dc5bfc28 100644
--- a/nuttx/configs/stm3240g-eval/telnetd/defconfig
+++ b/nuttx/configs/stm3240g-eval/telnetd/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm3240g-eval/webserver/defconfig b/nuttx/configs/stm3240g-eval/webserver/defconfig
index 7bd8e52ce..8f3ea36dc 100644
--- a/nuttx/configs/stm3240g-eval/webserver/defconfig
+++ b/nuttx/configs/stm3240g-eval/webserver/defconfig
@@ -203,7 +203,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm32f4discovery/nsh/defconfig b/nuttx/configs/stm32f4discovery/nsh/defconfig
index 0a07e8489..12848ddee 100644
--- a/nuttx/configs/stm32f4discovery/nsh/defconfig
+++ b/nuttx/configs/stm32f4discovery/nsh/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm32f4discovery/nxlines/defconfig b/nuttx/configs/stm32f4discovery/nxlines/defconfig
index 52705977a..f99af0233 100644
--- a/nuttx/configs/stm32f4discovery/nxlines/defconfig
+++ b/nuttx/configs/stm32f4discovery/nxlines/defconfig
@@ -197,7 +197,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm32f4discovery/ostest/defconfig b/nuttx/configs/stm32f4discovery/ostest/defconfig
index 5c120c614..8657d7edf 100644
--- a/nuttx/configs/stm32f4discovery/ostest/defconfig
+++ b/nuttx/configs/stm32f4discovery/ostest/defconfig
@@ -192,7 +192,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/configs/stm32f4discovery/pm/defconfig b/nuttx/configs/stm32f4discovery/pm/defconfig
index 592ce5701..4608c16c6 100644
--- a/nuttx/configs/stm32f4discovery/pm/defconfig
+++ b/nuttx/configs/stm32f4discovery/pm/defconfig
@@ -198,7 +198,7 @@ CONFIG_CAN2_BAUD=700000
 #
 # STM32F40xxx Ethernet device driver settings
 #
-CONFIG_STM32_PHYADDR=0x01
+CONFIG_STM32_PHYADDR=1
 CONFIG_STM32_MII=y
 CONFIG_STM32_MII_MCO1=y
 CONFIG_STM32_MII_MCO2=n
diff --git a/nuttx/include/nuttx/net/uip/uipopt.h b/nuttx/include/nuttx/net/uip/uipopt.h
index 4eff56fe8..9797e0482 100644
--- a/nuttx/include/nuttx/net/uip/uipopt.h
+++ b/nuttx/include/nuttx/net/uip/uipopt.h
@@ -296,7 +296,23 @@
 /* The size of the TCP read buffer size */
 
 #ifndef CONFIG_NET_TCP_READAHEAD_BUFSIZE
-# define CONFIG_NET_TCP_READAHEAD_BUFSIZE UIP_TCP_MSS
+#  if CONFIG_NET_NTCP_READAHEAD_BUFFERS < 1
+#    define CONFIG_NET_TCP_READAHEAD_BUFSIZE 0
+#  else
+#    define CONFIG_NET_TCP_READAHEAD_BUFSIZE UIP_TCP_MSS
+#  endif
+#endif
+
+/* Delay after receive to catch a following packet.  No delay should be
+ * required if TCP/IP read-ahead buffering is enabled.
+ */
+
+#ifndef CONFIG_NET_TCP_RECVDELAY
+#  if CONFIG_NET_NTCP_READAHEAD_BUFFERS > 0
+#    define CONFIG_NET_TCP_RECVDELAY 0
+#  else
+#    define CONFIG_NET_TCP_RECVDELAY 5
+#  endif
 #endif
 
 /****************************************************************************
diff --git a/nuttx/net/Kconfig b/nuttx/net/Kconfig
index b6e10a2e0..3d39dc1d7 100644
--- a/nuttx/net/Kconfig
+++ b/nuttx/net/Kconfig
@@ -112,16 +112,43 @@ config NET_MAX_LISTENPORTS
 		Maximum number of listening TCP/IP ports (all tasks).  Default: 20
 
 config NET_TCP_READAHEAD_BUFSIZE
-	bool "TCP/IP read-ahead buffer size"
+	int "TCP/IP read-ahead buffer size"
 	default 562
 	---help---
-		Size of TCP/IP read-ahead buffers
+		Read-ahead buffers allows buffering of TCP/IP packets when there is no
+		receive in place to catch the TCP packet.  In that case, the packet
+		will be retained in the NuttX read-ahead buffers.
+
+		This setting specifies the size of one TCP/IP read-ahead buffer.
+		This should best be a equal to the maximum packet size (NET_BUFSIZE).
 
 config NET_NTCP_READAHEAD_BUFFERS
 	int "Number of TCP/IP read-ahead buffers"
 	default 8
 	---help---
-		Number of TCP/IP read-ahead buffers (may be zero)
+		Read-ahead buffers allows buffering of TCP/IP packets when there is no
+		receive in place to catch the TCP packet.  In that case, the packet
+		will be retained in the NuttX read-ahead buffers.
+
+		This setting specifies the number of TCP/IP read-ahead buffers  This
+		value can be set to zero to disable all TCP/IP read-ahead buffering.
+		You might want to disable TCP/IP read-ahead buffering on a highly
+		memory constained system that does not have any TCP/IP packet rate
+		issues.
+
+config NET_TCP_RECVDELAY
+	int "TCP Rx delay"
+	default 0
+	---help---
+		If NET_NTCP_READAHEAD_BUFFERS is zero, then there will be no buffering
+		of TCP/IP packets:  Any TCP/IP packet received will be ACKed, but its contents
+		will be dropped in the bit-bucket.
+
+		One low-performance option is delay for a short period of time after a
+		TCP/IP packet is received to see if another comes right behind it. Then
+		the packet data from both can be combined.  This option only makes since
+		if performance is not an issue and you need to handle short bursts of
+		small, back-to-back packets.  The delay is in units of deciseconds.
 
 config NET_TCPBACKLOG
 	bool "TCP/IP backlog support"
diff --git a/nuttx/net/recvfrom.c b/nuttx/net/recvfrom.c
index 741cd4c72..6b9eb9a90 100644
--- a/nuttx/net/recvfrom.c
+++ b/nuttx/net/recvfrom.c
@@ -59,8 +59,6 @@
  * Definitions
  ****************************************************************************/
 
-#define TCP_TIMEO 10  /* Deciseconds after data received before recv() returns */
-
 #define UDPBUF ((struct uip_udpip_hdr *)&dev->d_buf[UIP_LLH_LEN])
 #define TCPBUF ((struct uip_tcpip_hdr *)&dev->d_buf[UIP_LLH_LEN])
 
@@ -354,31 +352,39 @@ static int recvfrom_timeout(struct recvfrom_s *pstate)
   FAR struct socket *psock = 0;
   socktimeo_t        timeo = 0;
 
-  /* If this is a TCP socket that has already received some data,
-   * than we will always use a short timeout.
+  /* Check for a timeout configured via setsockopts(SO_RCVTIMEO). If none...
+   * we well let the read hang forever (except for the special case below).
    */
 
-  if (pstate->rf_recvlen > 0)
+  /* Get the socket reference from the private data */
+
+  psock = pstate->rf_sock;
+  if (psock)
     {
-      /* Use the short timeout */
+      /* Recover the timeout value (zero if no timeout) */
 
-      timeo = TCP_TIMEO;
+      timeo = psock->s_rcvtimeo;
     }
 
-  /* No.. check for a timeout configured via setsockopts(SO_RCVTIMEO).
-   * If none... we well let the read hang forever.
+  /* Use a fixed, configurable delay under the following circumstances:
+   *
+   * 1) This delay function has been enabled with CONFIG_NET_TCP_RECVDELAY > 0
+   * 2) Some data has already been received from the socket.  Since this can
+   *    only be true for a TCP/IP socket, this logic applies only to TCP/IP
+   *    sockets, and either
+   * 3) There is no configured receive timeout, or
+   * 4) The configured receive timeout is greater than than the delay
    */
 
-  else
+#if CONFIG_NET_TCP_RECVDELAY > 0
+  if ((timeo == 0 || timeo > CONFIG_NET_TCP_RECVDELAY) &&
+      pstate->rf_recvlen > 0)
     {
-      /* Get the socket reference from the private data */
+      /* Use the configured timeout */
 
-      psock = pstate->rf_sock;
-      if (psock)
-        {
-          timeo = psock->s_rcvtimeo;
-        }
+      timeo = CONFIG_NET_TCP_RECVDELAY;
     }
+#endif
 
   /* Is there an effective timeout? */
 
@@ -389,7 +395,7 @@ static int recvfrom_timeout(struct recvfrom_s *pstate)
       return net_timeo(pstate->rf_starttime, timeo);
     }
 
-  /* No timeout */
+  /* No timeout -- hang forever waiting for data. */
 
   return FALSE;
 }
@@ -489,9 +495,28 @@ static uint16_t recvfrom_tcpinterrupt(struct uip_driver_s *dev, void *conn,
 
           flags = (flags & ~UIP_NEWDATA) | UIP_SNDACK;
 
-          /* If the user buffer has been filled, then we are finished. */
+          /* Check for transfer complete.  We will consider the transfer
+           * complete in own of two different ways, depending on the setting
+           * of CONFIG_NET_TCP_RECVDELAY.
+           *
+           * 1) If CONFIG_NET_TCP_RECVDELAY == 0 then we will consider the
+           *    TCP/IP transfer complete as soon as any data has been received.
+           *    This is safe because if any additional data is received, it
+           *    will be retained inthe TCP/IP read-ahead buffer until the
+           *    next receive is performed.
+           * 2) CONFIG_NET_TCP_RECVDELAY > 0 may be set to wait a little
+           *    bit to determine if more data will be received.  You might
+           *    do this if read-ahead buffereing is disabled and we want to
+           *    minimize the loss of back-to-back packets.  In this case,
+           *    the transfer is complete when either a) the entire user buffer 
+           *    is full or 2) when the receive timeout occurs (below).
+           */
 
+#if CONFIG_NET_TCP_RECVDELAY > 0
           if (pstate->rf_buflen == 0)
+#else
+          if (pstate->rf_recvlen > 0)
+#endif
             {
               nllvdbg("TCP resume\n");