net: make ARP timeout configurable

Currently the timeout waiting for an ARP reply is hard set to 5 seconds.
On i.MX31ADS due to a hardware "strangeness" up to four first IP packets
to the boards get lost, which typically are ARP replies. By configuring
the timeout to a lower value we significantly improve the first network
transfer time on this board. The timeout is specified in milliseconds,
later internally it is converted to deciseconds, because it has to be
converted to hardware ticks, and CFG_HZ ranges from 900 to 27000000 on
different boards.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

README

@@ -1561,6 +1561,10 @@ The following options need to be configured:
 		before giving up the operation. If not defined, a
 		default value of 5 is used.
 
+		CONFIG_ARP_TIMEOUT
+
+		Timeout waiting for an ARP reply in milliseconds.
+
 - Command Interpreter:
 		CONFIG_AUTO_COMPLETE
 

net/net.c

@@ -94,11 +94,22 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#define ARP_TIMEOUT		5UL		/* Seconds before trying ARP again */
+#ifndef	CONFIG_ARP_TIMEOUT
+# define ARP_TIMEOUT		50UL	/* Deciseconds before trying ARP again */
+#elif (CONFIG_ARP_TIMEOUT < 100)
+# error "Due to possible overflow CONFIG_ARP_TIMEOUT must be greater than 100ms"
+#else
+# if (CONFIG_ARP_TIMEOUT % 100)
+#  warning "Supported ARP_TIMEOUT precision is 100ms"
+# endif
+# define ARP_TIMEOUT		(CONFIG_ARP_TIMEOUT / 100)
+#endif
+
+
 #ifndef	CONFIG_NET_RETRY_COUNT
 # define ARP_TIMEOUT_COUNT	5	/* # of timeouts before giving up  */
 #else
-# define ARP_TIMEOUT_COUNT  (CONFIG_NET_RETRY_COUNT)
+# define ARP_TIMEOUT_COUNT	CONFIG_NET_RETRY_COUNT
 #endif
 
 #if 0
@@ -129,7 +140,7 @@ uchar		NetOurEther[6];		/* Our ethernet address			*/
 uchar		NetServerEther[6] =	/* Boot server enet address		*/
 			{ 0, 0, 0, 0, 0, 0 };
 IPaddr_t	NetOurIP;		/* Our IP addr (0 = unknown)		*/
-IPaddr_t	NetServerIP;		/* Our IP addr (0 = unknown)		*/
+IPaddr_t	NetServerIP;		/* Server IP addr (0 = unknown)		*/
 volatile uchar *NetRxPkt;		/* Current receive packet		*/
 int		NetRxPktLen;		/* Current rx packet length		*/
 unsigned	NetIPID;		/* IP packet ID				*/
@@ -253,7 +264,7 @@ void ArpTimeoutCheck(void)
 	t = get_timer(0);
 
 	/* check for arp timeout */
-	if ((t - NetArpWaitTimerStart) > ARP_TIMEOUT * CFG_HZ) {
+	if ((t - NetArpWaitTimerStart) > ARP_TIMEOUT * CFG_HZ / 10) {
 		NetArpWaitTry++;
 
 		if (NetArpWaitTry >= ARP_TIMEOUT_COUNT) {