[PATCH 07/11] arm-dt: parse devtree pointer on boot

[Jeremy Kerr]

Add code to parse the device tree pointer from the atags, and an (empty)
routine to create an mdesc from the discovered device tree.

Split the parsing code in setup_arch to handle both device-tree and tags
based machine discovery.

Signed-off-by: Jeremy Kerr <jeremy.kerr at canonical.com>

---
 arch/arm/include/asm/devtree.h |   22 +++++++++
 arch/arm/kernel/Makefile       |    1 
 arch/arm/kernel/devtree.c      |   14 +++++
 arch/arm/kernel/setup.c        |   80 +++++++++++++++++++++------------
 4 files changed, 90 insertions(+), 27 deletions(-)

diff --git a/arch/arm/include/asm/devtree.h b/arch/arm/include/asm/devtree.h
new file mode 100644
index 0000000..0914ac2
--- /dev/null
+++ b/arch/arm/include/asm/devtree.h
@@ -0,0 +1,22 @@
+/*
+ *  linux/arch/arm/include/asm/devtree.h
+ *
+ *  Copyright (C) 2009 Canonical Ltd. <jeremy.kerr at canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifdef CONFIG_ARM_DEVTREE
+
+extern struct machine_desc *parse_devicetree(void *devtree);
+
+#else
+
+static inline struct machine_desc *parse_devicetree(void *devtree)
+{
+	return NULL;
+}
+
+#endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 79087dd..45d2d82 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_ARM_THUMBEE)	+= thumbee.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_ARM_UNWIND)	+= unwind.o
 obj-$(CONFIG_HAVE_TCM)		+= tcm.o
+obj-$(CONFIG_ARM_DEVTREE)	+= devtree.o
 
 obj-$(CONFIG_CRUNCH)		+= crunch.o crunch-bits.o
 AFLAGS_crunch-bits.o		:= -Wa,-mcpu=ep9312
diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
new file mode 100644
index 0000000..864eab5
--- /dev/null
+++ b/arch/arm/kernel/devtree.c
@@ -0,0 +1,14 @@
+/*
+ *  linux/arch/arm/kernel/devtree.c
+ *
+ *  Copyright (C) 2009 Canonical Ltd. <jeremy.kerr at canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+struct machine_desc * __init parse_devicetree(void *devtree)
+{
+	return NULL;
+}
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e662d17..8abb4be 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -42,6 +42,7 @@
 #include <asm/mach/time.h>
 #include <asm/traps.h>
 #include <asm/unwind.h>
+#include <asm/devtree.h>
 
 #include "compat.h"
 #include "atags.h"
@@ -636,6 +637,17 @@ static void __init parse_tags(const struct tag *t)
 				t->hdr.tag);
 }
 
+static void * __init find_devtree(const struct tag *tags)
+{
+	const struct tag *t;
+
+	for_each_tag(t, tags)
+		if (t->hdr.tag == ATAG_DEVTREE)
+			return __va(t->u.devtree.devtree);
+
+	return NULL;
+}
+
 /*
  * This holds our defaults.
  */
@@ -692,48 +704,62 @@ void __init setup_arch(char **cmdline_p)
 	struct tag *tags = (struct tag *)&init_tags;
 	struct machine_desc *mdesc;
 	char *from = default_command_line;
+	void *devtree;
 
 	unwind_init();
 
 	setup_processor();
-	mdesc = setup_machine(machine_arch_type);
-	machine_name = mdesc->name;
-
-	if (mdesc->soft_reboot)
-		reboot_setup("s");
 
 	if (__atags_pointer)
 		tags = phys_to_virt(__atags_pointer);
-	else if (mdesc->boot_params)
-		tags = phys_to_virt(mdesc->boot_params);
 
-	/*
-	 * If we have the old style parameters, convert them to
-	 * a tag list.
-	 */
-	if (tags->hdr.tag != ATAG_CORE)
-		convert_to_tag_list(tags);
-	if (tags->hdr.tag != ATAG_CORE)
-		tags = (struct tag *)&init_tags;
-
-	if (mdesc->fixup)
-		mdesc->fixup(mdesc, tags, &from, &meminfo);
-
-	if (tags->hdr.tag == ATAG_CORE) {
-		if (meminfo.nr_banks != 0)
-			squash_mem_tags(tags);
-		save_atags(tags);
-		parse_tags(tags);
+	devtree = find_devtree(tags);
+	if (devtree) {
+		mdesc = parse_devicetree(devtree);
+
+		/*
+		 * todo: fallback to arch-number-based mdesc discovery
+		 * if device tree doesn't match
+		 */
+	} else {
+		mdesc = setup_machine(machine_arch_type);
+
+		if (!__atags_pointer && mdesc->boot_params)
+			tags = phys_to_virt(mdesc->boot_params);
+
+		/*
+		 * If we have the old style parameters, convert them to
+		 * a tag list.
+		 */
+		if (tags->hdr.tag != ATAG_CORE)
+			convert_to_tag_list(tags);
+		if (tags->hdr.tag != ATAG_CORE)
+			tags = (struct tag *)&init_tags;
+
+		if (mdesc->fixup)
+			mdesc->fixup(mdesc, tags, &from, &meminfo);
+
+		if (tags->hdr.tag == ATAG_CORE) {
+			if (meminfo.nr_banks != 0)
+				squash_mem_tags(tags);
+			save_atags(tags);
+			parse_tags(tags);
+		}
+
+		/* Copy discovered command line to boot_command_line */
+		strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);
+
 	}
 
+	machine_name = mdesc->name;
+	if (mdesc->soft_reboot)
+		reboot_setup("s");
+
 	init_mm.start_code = (unsigned long) _text;
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
 	init_mm.brk	   = (unsigned long) _end;
 
-	/* parse_early_param needs a boot_command_line */
-	strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);
-
 	/* populate cmd_line too for later use, preserving boot_command_line */
 	strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
 	*cmdline_p = cmd_line;