loader: fdt: Try to load every possible DTB from u-boot

U-Boot setup a few variables :

 - fdt_addr which is the board static dtb (most of the time loaded before
   u-boot or coming from some hardware like a ROM)
 - fdt_addr_r which is a location in RAM that holds the DTB loaded by
   u-boot or before u-boot

In the case of u-boot + rpi firmware the DTB is loaded in RAM but the location
still end up in the fdt_addr variable and the fdt_addr_r variable exist.

Change the behavior so we test that a DTB exists for every possible variable :

 - fdt_addr_r is checked first as if u-boot needed to modify it the
   correct DTB will live there.
 - fdt_addr is checked second as if we run on a hardware with DTB in ROM
   it means that we what/need to run that
 - fdtaddr looks like a FreeBSD-ism but since I'm not sure leave it.

Reviewed by:	gonzo
Differential Revision:	https://reviews.freebsd.org/D16101

1 files changed, 30 insertions, 16 deletions

diff --git a/stand/uboot/fdt/uboot_fdt.c b/stand/uboot/fdt/uboot_fdt.c
index aed7885e961cf..417ec4aeb6eb5 100644
--- a/stand/uboot/fdt/uboot_fdt.c
+++ b/stand/uboot/fdt/uboot_fdt.c
@@ -39,6 +39,30 @@ __FBSDID("$FreeBSD$");
 #define STR(number) #number
 #define STRINGIFY(number) STR(number)
 
+static int
+fdt_platform_load_from_ubenv(const char *var)
+{
+	struct fdt_header *hdr;
+	const char *s;
+	char *p;
+
+	s = ub_env_get(var);
+	if (s == NULL || *s == '\0')
+		return (1);
+
+	hdr = (struct fdt_header *)strtoul(s, &p, 16);
+	if (*p != '\0')
+		return (1);
+
+	if (fdt_load_dtb_addr(hdr) == 0) {
+		printf("Using DTB provided by U-Boot at "
+		    "address %p.\n", hdr);
+		return (0);
+	}
+
+	return (1);
+}
+
 int
 fdt_platform_load_dtb(void)
 {
@@ -53,22 +77,12 @@ fdt_platform_load_dtb(void)
 	 * variable for fdt data loaded into ram is fdt_addr_r, so try that
 	 * first.  Board vendors also use both fdtaddr and fdt_addr names.
 	 */
-	s = ub_env_get("fdt_addr_r");
-	if (s == NULL)
-		s = ub_env_get("fdtaddr");
-	if (s == NULL)
-		s = ub_env_get("fdt_addr");
-	if (s != NULL && *s != '\0') {
-		hdr = (struct fdt_header *)strtoul(s, &p, 16);
-		if (*p == '\0') {
-			if (fdt_load_dtb_addr(hdr) == 0) {
-				printf("Using DTB provided by U-Boot at "
-				    "address %p.\n", hdr);
-				rv = 0;
-				goto exit;
-			}
-		}
-	}
+	if ((rv = fdt_platform_load_from_ubenv("fdt_addr_r")) == 0)
+		goto exit;
+	if ((rv = fdt_platform_load_from_ubenv("fdt_addr")) == 0)
+		goto exit;
+	if ((rv = fdt_platform_load_from_ubenv("fdtaddr")) == 0)
+		goto exit;
 
 	rv = 1;