fdt: Avoid early panic() when there is no FDT present

CONFIG_OF_CONTROL requires a valid device tree. However, we cannot call
panic() before the console is set up since the message does not appear,
and we get a silent failure.

Remove the panic from fdtdec_check_fdt() and provide a new function to
prepare the fdt for use. This will be called after the console is ready.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

include/fdtdec.h

@@ -155,8 +155,21 @@ s32 fdtdec_get_int(const void *blob, int node, const char *prop_name,
 int fdtdec_get_is_enabled(const void *blob, int node);
 
 /**
- * Checks whether we have a valid fdt available to control U-Boot, and panic
- * if not.
+ * Make sure we have a valid fdt available to control U-Boot.
+ *
+ * If not, a message is printed to the console if the console is ready.
+ *
+ * @return 0 if all ok, -1 if not
+ */
+int fdtdec_prepare_fdt(void);
+
+/**
+ * Checks that we have a valid fdt available to control U-Boot.
+
+ * However, if not then for the moment nothing is done, since this function
+ * is called too early to panic().
+ *
+ * @returns 0
  */
 int fdtdec_check_fdt(void);
 

lib/fdtdec.c

@@ -262,17 +262,31 @@ int fdtdec_find_aliases_for_id(const void *blob, const char *name,
 	return num_found;
 }
 
+int fdtdec_check_fdt(void)
+{
+	/*
+	 * We must have an FDT, but we cannot panic() yet since the console
+	 * is not ready. So for now, just assert(). Boards which need an early
+	 * FDT (prior to console ready) will need to make their own
+	 * arrangements and do their own checks.
+	 */
+	assert(!fdtdec_prepare_fdt());
+	return 0;
+}
+
 /*
  * This function is a little odd in that it accesses global data. At some
  * point if the architecture board.c files merge this will make more sense.
  * Even now, it is common code.
  */
-int fdtdec_check_fdt(void)
+int fdtdec_prepare_fdt(void)
 {
-	/* We must have an fdt */
-	if (((uintptr_t)gd->fdt_blob & 3) || fdt_check_header(gd->fdt_blob))
-		panic("No valid fdt found - please append one to U-Boot\n"
-			"binary or define CONFIG_OF_EMBED\n");
+	if (((uintptr_t)gd->fdt_blob & 3) || fdt_check_header(gd->fdt_blob)) {
+		printf("No valid FDT found - please append one to U-Boot "
+			"binary, use u-boot-dtb.bin or define "
+			"CONFIG_OF_EMBED\n");
+		return -1;
+	}
 	return 0;
 }