allow ports to override go behavior

Split the arch-specific logic out of the common go code and into a dedicated
weak function called do_go_exec() that lives in cpu directories.  This will
need review from i386/nios people to make sure I didn't break them.

common/cmd_boot.c

@@ -28,25 +28,11 @@
 #include <command.h>
 #include <net.h>
 
-#if defined(CONFIG_I386)
-DECLARE_GLOBAL_DATA_PTR;
-#endif
-
-static inline void go_setup(int argc, char *argv[])
+/* Allow ports to override the default behavior */
+__attribute__((weak))
+unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char *argv[])
 {
-#if defined(CONFIG_I386)
-	/*
-	 * x86 does not use a dedicated register to pass the pointer
-	 * to the global_data
-	 */
-	argv[0] = (char *)gd;
-
-#elif defined(CONFIG_BLACKFIN)
-	if (dcache_status ())
-		dcache_disable ();
-	if (icache_status ())
-		icache_disable ();
-#endif
+	return entry (argc, argv);
 }
 
 int do_go (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
@@ -63,20 +49,11 @@ int do_go (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 
 	printf ("## Starting application at 0x%08lX ...\n", addr);
 
-	go_setup(argc, argv);
-
-#if defined(CONFIG_NIOS)
-	/*
-	 * Nios function pointers are address >> 1
-	 */
-	addr >>= 1;
-#endif
-
 	/*
 	 * pass address parameter as argv[0] (aka command name),
 	 * and all remaining args
 	 */
-	rc = ((ulong (*)(int, char *[]))addr) (--argc, &argv[1]);
+	rc = do_go_exec ((void *)addr, argc - 1, argv + 1);
 	if (rc != 0) rcode = 1;
 
 	printf ("## Application terminated, rc = 0x%lX\n", rc);

lib_i386/board.c

@@ -421,3 +421,11 @@ void hang (void)
 	puts ("### ERROR ### Please RESET the board ###\n");
 	for (;;);
 }
+
+unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char *argv[])
+{
+	/*
+	 * Nios function pointers are address >> 1
+	 */
+	return (entry >> 1) (argc, argv);
+}

lib_nios/board.c

@@ -190,3 +190,13 @@ void hang (void)
 	puts("### ERROR ### Please reset board ###\n");
 	for (;;);
 }
+
+unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char *argv[])
+{
+	/*
+	 * x86 does not use a dedicated register to pass the pointer
+	 * to the global_data
+	 */
+	argv[-1] = (char *)gd;
+	return entry (argc, argv);
+}