[PATCH 1/2] librem5: properly set the `fdtfile` env variable

[Arnaud Ferraris]

In order to use the generic "distro boot" using an extlinux.conf file,
the `fdtfile` environment variable is mandatory. This commit ensure this
variable is properly constructed based on the detected board revision.

Signed-off-by: Arnaud Ferraris <arnaud.ferraris at collabora.com>
---
 board/purism/librem5/librem5.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/board/purism/librem5/librem5.c b/board/purism/librem5/librem5.c
index 386ed1b4fb..d0249e71f0 100644
--- a/board/purism/librem5/librem5.c
+++ b/board/purism/librem5/librem5.c
@@ -399,21 +399,46 @@ int board_init(void)
 int board_late_init(void)
 {
 	if (IS_ENABLED(CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG)) {
-		u32 rev;
+		/*
+		 * Use the r4 dtb by default as those are the most
+		 * widespread devices.
+		 */
+		u32 rev, dtb_rev = 4;
 		char rev_str[3];
+		char fdt_str[50];
 
 		env_set("board_name", "librem5");
 		if (fuse_read(9, 0, &rev)) {
 			env_set("board_rev", BOARD_REV_ERROR);
 		} else if (rev == 0) {
+			/*
+			 * If the fuses aren't burnt we should use either the
+			 * r2 or r3 DTB. The latter makes more sense as there
+			 * are far more r3 devices out there.
+			 */
+			dtb_rev = 3;
 			env_set("board_rev", BOARD_REV_UNKNOWN);
 		} else if (rev > 0) {
+			if (rev == 1)
+				dtb_rev = 2;
+			else if (rev < dtb_rev)
+				dtb_rev = rev;
+			/*
+			 * FCC-approved devices report '5' as their board
+			 * revision but use the r4 DTB as the PCB's are
+			 * functionally identical.
+			 */
+			else if (rev == 5)
+				dtb_rev = 4;
 			sprintf(rev_str, "%u", rev);
 			env_set("board_rev", rev_str);
 		}
 
 		printf("Board name: %s\n", env_get("board_name"));
 		printf("Board rev:  %s\n", env_get("board_rev"));
+
+		sprintf(fdt_str, "freescale/imx8mq-librem5-r%u.dtb", dtb_rev);
+		env_set("fdtfile", fdt_str);
 	}
 
 	if (is_usb_boot()) {
-- 
2.42.0