6 files changed, 184 insertions, 2 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c66e0808c2b1..73c320ea172c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1801,6 +1801,18 @@ config ARM_APPENDED_DTB
           location into r2 of a bootloader provided DTB is always preferable
           to this option.
 
+config ARM_ATAG_DTB_COMPAT
+        bool "Supplement the appended DTB with traditional ATAG information"
+        depends on ARM_APPENDED_DTB
+        help
+          Some old bootloaders can't be updated to a DTB capable one, yet
+          they provide ATAGs with memory configuration, the ramdisk address,
+          the kernel cmdline string, etc.  Such information is dynamically
+          provided by the bootloader and can't always be stored in a static
+          DTB.  To allow a device tree enabled kernel to be used with such
+          bootloaders, this option allows zImage to extract the information
+          from the ATAG list and store it at run time into the appended DTB.
+
 config CMDLINE
         string "Default kernel command string"
         default ""
diff --git a/arch/arm/boot/compressed/.gitignore b/arch/arm/boot/compressed/.gitignore
index c6028967d336..e0936a148516 100644
--- a/arch/arm/boot/compressed/.gitignore
+++ b/arch/arm/boot/compressed/.gitignore
@@ -5,3 +5,12 @@ piggy.lzo
 piggy.lzma
 vmlinux
 vmlinux.lds
+
+# borrowed libfdt files
+fdt.c
+fdt.h
+fdt_ro.c
+fdt_rw.c
+fdt_wip.c
+libfdt.h
+libfdt_internal.h
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index c20ddc69d950..55f86349d547 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -93,19 +93,36 @@ suffix_$(CONFIG_KERNEL_GZIP) = gzip
 suffix_$(CONFIG_KERNEL_LZO)  = lzo
 suffix_$(CONFIG_KERNEL_LZMA) = lzma
 
+# Borrowed libfdt files for the ATAG compatibility mode
+
+libfdt          := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c
+libfdt_hdrs     := fdt.h libfdt.h libfdt_internal.h
+
+libfdt_objs     := $(addsuffix .o, $(basename $(libfdt)))
+
+$(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/%
+        $(call cmd,shipped)
+
+$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \
+        $(addprefix $(obj)/,$(libfdt_hdrs))
+
+ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y)
+OBJS    += $(libfdt_objs) atags_to_fdt.o
+endif
+
 targets       := vmlinux vmlinux.lds \
                  piggy.$(suffix_y) piggy.$(suffix_y).o \
                  font.o font.c head.o misc.o $(OBJS)
 
 # Make sure files are removed during clean
-extra-y       += piggy.gzip piggy.lzo piggy.lzma lib1funcs.S
+extra-y       += piggy.gzip piggy.lzo piggy.lzma lib1funcs.S $(libfdt) $(libfdt_hdrs)
 
 ifeq ($(CONFIG_FUNCTION_TRACER),y)
 ORIG_CFLAGS := $(KBUILD_CFLAGS)
 KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
 endif
 
-ccflags-y := -fpic -fno-builtin
+ccflags-y := -fpic -fno-builtin -I$(obj)
 asflags-y := -Wa,-march=all
 
 # Supply kernel BSS size to the decompressor via a linker symbol.
diff --git a/arch/arm/boot/compressed/atags_to_fdt.c b/arch/arm/boot/compressed/atags_to_fdt.c
new file mode 100644
index 000000000000..6ce11c481178
--- /dev/null
+++ b/arch/arm/boot/compressed/atags_to_fdt.c
@@ -0,0 +1,97 @@
+#include <asm/setup.h>
+#include <libfdt.h>
+
+static int node_offset(void *fdt, const char *node_path)
+{
+        int offset = fdt_path_offset(fdt, node_path);
+        if (offset == -FDT_ERR_NOTFOUND)
+                offset = fdt_add_subnode(fdt, 0, node_path);
+        return offset;
+}
+
+static int setprop(void *fdt, const char *node_path, const char *property,
+                   uint32_t *val_array, int size)
+{
+        int offset = node_offset(fdt, node_path);
+        if (offset < 0)
+                return offset;
+        return fdt_setprop(fdt, offset, property, val_array, size);
+}
+
+static int setprop_string(void *fdt, const char *node_path,
+                          const char *property, const char *string)
+{
+        int offset = node_offset(fdt, node_path);
+        if (offset < 0)
+                return offset;
+        return fdt_setprop_string(fdt, offset, property, string);
+}
+
+static int setprop_cell(void *fdt, const char *node_path,
+                        const char *property, uint32_t val)
+{
+        int offset = node_offset(fdt, node_path);
+        if (offset < 0)
+                return offset;
+        return fdt_setprop_cell(fdt, offset, property, val);
+}
+
+/*
+ * Convert and fold provided ATAGs into the provided FDT.
+ *
+ * REturn values:
+ *    = 0 -> pretend success
+ *    = 1 -> bad ATAG (may retry with another possible ATAG pointer)
+ *    < 0 -> error from libfdt
+ */
+int atags_to_fdt(void *atag_list, void *fdt, int total_space)
+{
+        struct tag *atag = atag_list;
+        uint32_t mem_reg_property[2 * NR_BANKS];
+        int memcount = 0;
+        int ret;
+
+        /* make sure we've got an aligned pointer */
+        if ((u32)atag_list & 0x3)
+                return 1;
+
+        /* if we get a DTB here we're done already */
+        if (*(u32 *)atag_list == fdt32_to_cpu(FDT_MAGIC))
+               return 0;
+
+        /* validate the ATAG */
+        if (atag->hdr.tag != ATAG_CORE ||
+            (atag->hdr.size != tag_size(tag_core) &&
+             atag->hdr.size != 2))
+                return 1;
+
+        /* let's give it all the room it could need */
+        ret = fdt_open_into(fdt, fdt, total_space);
+        if (ret < 0)
+                return ret;
+
+        for_each_tag(atag, atag_list) {
+                if (atag->hdr.tag == ATAG_CMDLINE) {
+                        setprop_string(fdt, "/chosen", "bootargs",
+                                        atag->u.cmdline.cmdline);
+                } else if (atag->hdr.tag == ATAG_MEM) {
+                        if (memcount >= sizeof(mem_reg_property)/4)
+                                continue;
+                        mem_reg_property[memcount++] = cpu_to_fdt32(atag->u.mem.start);
+                        mem_reg_property[memcount++] = cpu_to_fdt32(atag->u.mem.size);
+                } else if (atag->hdr.tag == ATAG_INITRD2) {
+                        uint32_t initrd_start, initrd_size;
+                        initrd_start = atag->u.initrd.start;
+                        initrd_size = atag->u.initrd.size;
+                        setprop_cell(fdt, "/chosen", "linux,initrd-start",
+                                        initrd_start);
+                        setprop_cell(fdt, "/chosen", "linux,initrd-end",
+                                        initrd_start + initrd_size);
+                }
+        }
+
+        if (memcount)
+                setprop(fdt, "/memory", "reg", mem_reg_property, 4*memcount);
+
+        return fdt_pack(fdt);
+}
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index ba5c552f8c69..9f5ac11ccd8e 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -246,6 +246,38 @@ restart:	adr	r0, LC0
                 cmp     lr, r1
                 bne     dtb_check_done          @ not found
 
+#ifdef CONFIG_ARM_ATAG_DTB_COMPAT
+                /*
+                 * OK... Let's do some funky business here.
+                 * If we do have a DTB appended to zImage, and we do have
+                 * an ATAG list around, we want the later to be translated
+                 * and folded into the former here.  To be on the safe side,
+                 * let's temporarily move  the stack away into the malloc
+                 * area.  No GOT fixup has occurred yet, but none of the
+                 * code we're about to call uses any global variable.
+                */
+                add     sp, sp, #0x10000
+                stmfd   sp!, {r0-r3, ip, lr}
+                mov     r0, r8
+                mov     r1, r6
+                sub     r2, sp, r6
+                bl      atags_to_fdt
+
+                /*
+                 * If returned value is 1, there is no ATAG at the location
+                 * pointed by r8.  Try the typical 0x100 offset from start
+                 * of RAM and hope for the best.
+                 */
+                cmp     r0, #1
+                sub     r0, r4, #(TEXT_OFFSET - 0x100)
+                mov     r1, r6
+                sub     r2, sp, r6
+                blne    atags_to_fdt
+
+                ldmfd   sp!, {r0-r3, ip, lr}
+                sub     sp, sp, #0x10000
+#endif
+
                 mov     r8, r6                  @ use the appended device tree
 
                 /*
diff --git a/arch/arm/boot/compressed/libfdt_env.h b/arch/arm/boot/compressed/libfdt_env.h
new file mode 100644
index 000000000000..1f4e71876b00
--- /dev/null
+++ b/arch/arm/boot/compressed/libfdt_env.h
@@ -0,0 +1,15 @@
+#ifndef _ARM_LIBFDT_ENV_H
+#define _ARM_LIBFDT_ENV_H
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <asm/byteorder.h>
+
+#define fdt16_to_cpu(x)         be16_to_cpu(x)
+#define cpu_to_fdt16(x)         cpu_to_be16(x)
+#define fdt32_to_cpu(x)         be32_to_cpu(x)
+#define cpu_to_fdt32(x)         cpu_to_be32(x)
+#define fdt64_to_cpu(x)         be64_to_cpu(x)
+#define cpu_to_fdt64(x)         cpu_to_be64(x)
+
+#endif