From d000dd2f8692c5b60121091d1252e8a677c926c3 Mon Sep 17 00:00:00 2001
From: Ian Lepore <ian@FreeBSD.org>
Date: Sat, 22 Feb 2014 19:10:58 +0000
Subject: [PATCH] Change fdt_setup_fdtp() from "guess then fail" to more
 probe-like behavior.

The old code basically said it was going to use some particular blob
without knowing whether it could successfully do so, then it would invoke
the function to do that and return its status.  If it failed, you were
done, even if other blobs might be available.  Now the code attempts to use
some particular blob and if that succeeds it says so and returns success,
otherwise it moves on to try another potential blob.

One specific problem this solves is when u-boot sets an fdtaddr variable
to point to some memory address, then doesn't actually load a blob at
that address.  Now the header check will fail, and the code will move
on to the fallback dtb compiled into the kernel (if any).
---
 sys/boot/fdt/fdt_loader_cmd.c | 63 +++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 18 deletions(-)

diff --git a/sys/boot/fdt/fdt_loader_cmd.c b/sys/boot/fdt/fdt_loader_cmd.c
index d8ad9426bd72..b553a85f8572 100644
--- a/sys/boot/fdt/fdt_loader_cmd.c
+++ b/sys/boot/fdt/fdt_loader_cmd.c
@@ -128,6 +128,8 @@ fdt_find_static_dtb()
 	char *strp;
 	int i, sym_count;
 
+	debugf("fdt_find_static_dtb()\n");
+
 	sym_count = symtab = strtab = 0;
 	strp = NULL;
 
@@ -189,6 +191,8 @@ fdt_load_dtb(vm_offset_t va)
 	struct fdt_header header;
 	int err;
 
+	debugf("fdt_load_dtb(0x%08jx)\n", (uintmax_t)va);
+
 	COPYOUT(va, &header, sizeof(header));
 	err = fdt_check_header(&header);
 	if (err < 0) {
@@ -229,6 +233,8 @@ fdt_load_dtb_addr(struct fdt_header *header)
 {
 	int err;
 
+	debugf("fdt_load_dtb_addr(0x%p)\n", header);
+
 	fdtp_size = fdt_totalsize(header);
 	err = fdt_check_header(header);
 	if (err < 0) {
@@ -252,39 +258,58 @@ fdt_setup_fdtp()
 {
 	struct preloaded_file *bfp;
 	struct fdt_header *hdr;
+	int err;
 	const char *s;
 	char *p;
 	vm_offset_t va;
 	
+	debugf("fdt_setup_fdtp()\n");
+
+	/* If we already loaded a file, use it. */
 	if ((bfp = file_findfile(NULL, "dtb")) != NULL) {
-		printf("Using DTB from loaded file.\n");
-		return fdt_load_dtb(bfp->f_addr);
-	}
-	
-	if (fdt_to_load != NULL) {
-		printf("Using DTB from memory address 0x%08X.\n",
-		    (unsigned int)fdt_to_load);
-		return fdt_load_dtb_addr(fdt_to_load);
+		if (fdt_load_dtb(bfp->f_addr) == 0) {
+			printf("Using DTB from loaded file.\n");
+			return (0);
+		}
 	}
 
-	/* Board vendors use both fdtaddr and fdt_addr names.  Grrrr. */
+	/* If we were given the address of a valid blob in memory, use it. */
+	if (fdt_to_load != NULL) {
+		if (fdt_load_dtb_addr(fdt_to_load) == 0) {
+			printf("Using DTB from memory address 0x%08X.\n",
+			    (unsigned int)fdt_to_load);
+			return (0);
+		}
+	}
+
+	/*
+	 * If the U-boot environment contains a variable giving the address of a
+	 * valid blob in memory, use it.  Board vendors use both fdtaddr and
+	 * fdt_addr names.
+	 */
 	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') {
-			printf("Using DTB provided by U-Boot.\n");
-			return fdt_load_dtb_addr(hdr);
+			if (fdt_load_dtb_addr(hdr) == 0) {
+				printf("Using DTB provided by U-Boot at "
+				    "address 0x%08X.\n", hdr);
+				return (0);
+			}
+		}
+	}
+
+	/* If there is a dtb compiled into the kernel, use it. */
+	if ((va = fdt_find_static_dtb()) != 0) {
+		if (fdt_load_dtb(va) == 0) {
+			printf("Using DTB compiled into kernel.\n");
+			return (0);
 		}
 	}
 	
-	if ((va = fdt_find_static_dtb()) != 0) {
-		printf("Using DTB compiled into kernel.\n");
-		return (fdt_load_dtb(va));
-	}
-	
-	command_errmsg = "no device tree blob found!";
+	command_errmsg = "No device tree blob found!\n";
 	return (1);
 }
 
@@ -678,6 +703,8 @@ fdt_fixup(void)
 	ethstr = NULL;
 	len = 0;
 
+	debugf("fdt_fixup()\n");
+
 	if (fdtp == NULL && fdt_setup_fdtp() != 0)
 		return (0);
 
@@ -741,7 +768,7 @@ int
 fdt_copy(vm_offset_t va)
 {
 	int err;
-
+	debugf("fdt_copy va 0x%08x\n", va);
 	if (fdtp == NULL) {
 		err = fdt_setup_fdtp();
 		if (err) {