arm/dt: probe for platforms via the device tree

If a dtb is passed to the kernel then the kernel needs to iterate
through compiled-in mdescs looking for one that matches and move the
dtb data to a safe location before it gets accidentally overwritten by
the kernel.

This patch creates a new function, setup_machine_fdt() which is
analogous to the setup_machine_atags() created in the previous patch.
It does all the early setup needed to use a device tree machine
description.

v5: - Print warning with neither dtb nor atags are passed to the kernel
    - Fix bug in setting of __machine_arch_type to the selected machine,
      not just the last machine in the list.
      Reported-by: Tixy <tixy@yxit.co.uk>
    - Copy command line directly into boot_command_line instead of cmd_line
v4: - Dump some output when a matching machine_desc cannot be found
v3: - Added processing of reserved list.
    - Backed out the v2 change that copied instead of reserved the
      dtb.  dtb is reserved again and the real problem was fixed by
      using alloc_bootmem_align() for early allocation of RAM for
      unflattening the tree.
    - Moved cmd_line and initrd changes to earlier patch to make series
      bisectable.
v2: Changed to save the dtb by copying into an allocated buffer.
    - Since the dtb will very likely be passed in the first 16k of ram
      where the interrupt vectors live, memblock_reserve() is
      insufficient to protect the dtb data.

[based on work originally written by Jeremy Kerr <jeremy.kerr@canonical.com>]
Tested-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 19 insertions, 4 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 42c2f0cedf1b..05db25ef3dd5 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -20,6 +20,7 @@
 #include <linux/screen_info.h>
 #include <linux/init.h>
 #include <linux/kexec.h>
+#include <linux/of_fdt.h>
 #include <linux/crash_dump.h>
 #include <linux/root_dev.h>
 #include <linux/cpu.h>
@@ -42,6 +43,7 @@
 #include <asm/cachetype.h>
 #include <asm/tlbflush.h>
 
+#include <asm/prom.h>
 #include <asm/mach/arch.h>
 #include <asm/mach/irq.h>
 #include <asm/mach/time.h>
@@ -309,7 +311,7 @@ static void __init cacheid_init(void)
  */
 extern struct proc_info_list *lookup_processor_type(unsigned int);
 
-static void __init early_print(const char *str, ...)
+void __init early_print(const char *str, ...)
 {
         extern void printascii(const char *);
         char buf[256];
@@ -439,7 +441,7 @@ void cpu_init(void)
             : "r14");
 }
 
-static void __init dump_machine_table(void)
+void __init dump_machine_table(void)
 {
         struct machine_desc *p;
 
@@ -837,8 +839,17 @@ static struct machine_desc * __init setup_machine_tags(unsigned int nr)
         if (tags->hdr.tag != ATAG_CORE)
                 convert_to_tag_list(tags);
 #endif
-        if (tags->hdr.tag != ATAG_CORE)
+
+        if (tags->hdr.tag != ATAG_CORE) {
+#if defined(CONFIG_OF)
+                /*
+                 * If CONFIG_OF is set, then assume this is a reasonably
+                 * modern system that should pass boot parameters
+                 */
+                early_print("Warning: Neither atags nor dtb found\n");
+#endif
                 tags = (struct tag *)&init_tags;
+        }
 
         if (mdesc->fixup)
                 mdesc->fixup(mdesc, tags, &from, &meminfo);
@@ -864,7 +875,9 @@ void __init setup_arch(char **cmdline_p)
         unwind_init();
 
         setup_processor();
-        mdesc = setup_machine_tags(machine_arch_type);
+        mdesc = setup_machine_fdt(__atags_pointer);
+        if (!mdesc)
+                mdesc = setup_machine_tags(machine_arch_type);
         machine_desc = mdesc;
         machine_name = mdesc->name;
 
@@ -887,6 +900,8 @@ void __init setup_arch(char **cmdline_p)
         paging_init(mdesc);
         request_standard_resources(mdesc);
 
+        unflatten_device_tree();
+
 #ifdef CONFIG_SMP
         if (is_smp())
                 smp_init_cpus();