cmd: bootm: add subcommand preload

Add a subcommand preload to bootm that execute the preload
stage on the image. Right now, it checks the signature
of the image with the pre-load header. If the check
succeed, the u-boot env variable 'loadaddr_verified'
is set to the address of the image (without the header).

It allows to run such commands:
tftp script.img && bootm preload $loadaddr && source $loadaddr_verified

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/cmd/bootm.c b/cmd/bootm.c
index 87d40d4..1f70ee9 100644
--- a/cmd/bootm.c
+++ b/cmd/bootm.c
@@ -44,6 +44,9 @@
 static struct cmd_tbl cmd_bootm_sub[] = {
 	U_BOOT_CMD_MKENT(start, 0, 1, (void *)BOOTM_STATE_START, "", ""),
 	U_BOOT_CMD_MKENT(loados, 0, 1, (void *)BOOTM_STATE_LOADOS, "", ""),
+#ifdef CONFIG_CMD_BOOTM_PRE_LOAD
+	U_BOOT_CMD_MKENT(preload, 0, 1, (void *)BOOTM_STATE_PRE_LOAD, "", ""),
+#endif
 #ifdef CONFIG_SYS_BOOT_RAMDISK_HIGH
 	U_BOOT_CMD_MKENT(ramdisk, 0, 1, (void *)BOOTM_STATE_RAMDISK, "", ""),
 #endif
@@ -57,6 +60,20 @@
 	U_BOOT_CMD_MKENT(go, 0, 1, (void *)BOOTM_STATE_OS_GO, "", ""),
 };
 
+#if defined(CONFIG_CMD_BOOTM_PRE_LOAD)
+static ulong bootm_get_addr(int argc, char *const argv[])
+{
+	ulong addr;
+
+	if (argc > 0)
+		addr = hextoul(argv[0], NULL);
+	else
+		addr = image_load_addr;
+
+	return addr;
+}
+#endif
+
 static int do_bootm_subcommand(struct cmd_tbl *cmdtp, int flag, int argc,
 			       char *const argv[])
 {
@@ -72,6 +89,10 @@
 		if (state == BOOTM_STATE_START)
 			state |= BOOTM_STATE_PRE_LOAD | BOOTM_STATE_FINDOS |
 				 BOOTM_STATE_FINDOTHER;
+#if defined(CONFIG_CMD_BOOTM_PRE_LOAD)
+		if (state == BOOTM_STATE_PRE_LOAD)
+			state |= BOOTM_STATE_START;
+#endif
 	} else {
 		/* Unrecognized command */
 		return CMD_RET_USAGE;
@@ -85,6 +106,12 @@
 
 	ret = do_bootm_states(cmdtp, flag, argc, argv, state, &images, 0);
 
+#if defined(CONFIG_CMD_BOOTM_PRE_LOAD)
+	if (!ret && (state & BOOTM_STATE_PRE_LOAD))
+		env_set_hex("loadaddr_verified",
+			    bootm_get_addr(argc, argv) + image_load_offset);
+#endif
+
 	return ret;
 }
 
@@ -177,6 +204,9 @@
 	"must be\n"
 	"issued in the order below (it's ok to not issue all sub-commands):\n"
 	"\tstart [addr [arg ...]]\n"
+#if defined(CONFIG_CMD_BOOTM_PRE_LOAD)
+	"\tpreload [addr [arg ..]] - run only the preload stage\n"
+#endif
 	"\tloados  - load OS image\n"
 #if defined(CONFIG_SYS_BOOT_RAMDISK_HIGH)
 	"\tramdisk - relocate initrd, set env initrd_start/initrd_end\n"