Add uboot "fdt_high" enviroment variable

Add a new "fdt_high" enviroment variable. This can be used to control (or prevent) the
relocation of the flattened device tree on boot. It can be used to prevent relocation
of the fdt into highmem.  The variable behaves similarly to the existing "initrd_high"
variable.

Signed-off-by: David A. Long <dave.long@linaro.org>

2 files changed, 58 insertions, 11 deletions

diff --git a/README b/README
index 1e2d4d33c0..6a601d2688 100644
--- a/README
+++ b/README
@@ -3305,6 +3305,15 @@ List of environment variables (most likely not complete):
 		  This can be used to load and uncompress arbitrary
 		  data.
 
+  fdt_high	- if set this restricts the maximum address that the
+		  flattened device tree will be copied into upon boot.
+		  If this is set to the special value 0xFFFFFFFF then
+		  the fdt will not be copied at all on boot.  For this
+		  to work it must reside in writable memory, have
+		  sufficient padding on the end of it for u-boot to
+		  add the information it needs into it, and the memory
+		  must be accessible by the kernel.
+
   i2cfast	- (PPC405GP|PPC405EP only)
 		  if set to 'y' configures Linux I2C driver for fast
 		  mode (400kHZ). This environment variable is used in
diff --git a/common/image.c b/common/image.c
index e542a57367..c6cd85ef91 100644
--- a/common/image.c
+++ b/common/image.c
@@ -1234,8 +1234,10 @@ int boot_relocate_fdt (struct lmb *lmb, char **of_flat_tree, ulong *of_size)
 {
 	void	*fdt_blob = *of_flat_tree;
 	void	*of_start = 0;
+	char	*fdt_high;
 	ulong	of_len = 0;
 	int	err;
+	int	disable_relocation = 0;
 
 	/* nothing to do */
 	if (*of_size == 0)
@@ -1249,26 +1251,62 @@ int boot_relocate_fdt (struct lmb *lmb, char **of_flat_tree, ulong *of_size)
 	/* position on a 4K boundary before the alloc_current */
 	/* Pad the FDT by a specified amount */
 	of_len = *of_size + CONFIG_SYS_FDT_PAD;
-	of_start = (void *)(unsigned long)lmb_alloc_base(lmb, of_len, 0x1000,
-			getenv_bootm_mapsize() + getenv_bootm_low());
+
+	/* If fdt_high is set use it to select the relocation address */
+	fdt_high = getenv("fdt_high");
+	if (fdt_high) {
+		void *desired_addr = (void *)simple_strtoul(fdt_high, NULL, 16);
+
+		if (((ulong) desired_addr) == ~0UL) {
+			/* All ones means use fdt in place */
+			desired_addr = fdt_blob;
+			disable_relocation = 1;
+		}
+		if (desired_addr) {
+			of_start =
+			    (void *)(ulong) lmb_alloc_base(lmb, of_len, 0x1000,
+							   ((ulong)
+							    desired_addr)
+							   + of_len);
+			if (desired_addr && of_start != desired_addr) {
+				puts("Failed using fdt_high value for Device Tree");
+				goto error;
+			}
+		} else {
+			of_start =
+			    (void *)(ulong) mb_alloc(lmb, of_len, 0x1000);
+		}
+	} else {
+		of_start =
+		    (void *)(ulong) lmb_alloc_base(lmb, of_len, 0x1000,
+						   getenv_bootm_mapsize()
+						   + getenv_bootm_low());
+	}
 
 	if (of_start == 0) {
 		puts("device tree - allocation error\n");
 		goto error;
 	}
 
-	debug ("## device tree at %p ... %p (len=%ld [0x%lX])\n",
-		fdt_blob, fdt_blob + *of_size - 1, of_len, of_len);
+	if (disable_relocation) {
+		/* We assume there is space after the existing fdt to use for padding */
+		fdt_set_totalsize(of_start, of_len);
+		printf("   Using Device Tree in place at %p, end %p\n",
+		       of_start, of_start + of_len - 1);
+	} else {
+		debug ("## device tree at %p ... %p (len=%ld [0x%lX])\n",
+			fdt_blob, fdt_blob + *of_size - 1, of_len, of_len);
 
-	printf ("   Loading Device Tree to %p, end %p ... ",
-		of_start, of_start + of_len - 1);
+		printf ("   Loading Device Tree to %p, end %p ... ",
+			of_start, of_start + of_len - 1);
 
-	err = fdt_open_into (fdt_blob, of_start, of_len);
-	if (err != 0) {
-		fdt_error ("fdt move failed");
-		goto error;
+		err = fdt_open_into (fdt_blob, of_start, of_len);
+		if (err != 0) {
+			fdt_error ("fdt move failed");
+			goto error;
+		}
+		puts ("OK\n");
 	}
-	puts ("OK\n");
 
 	*of_flat_tree = of_start;
 	*of_size = of_len;