microblaze: Final support for statically linked DTB

If r7 is zero at kernel boot, or does not point to a valid DTB, then
we fall back to a DTB (assumed to be) linked statically in the kernel, instead
of blindly copying bogus cruft into the kernel DTB memory region

Signed-off-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

3 files changed, 26 insertions, 15 deletions

diff --git a/arch/microblaze/include/asm/prom.h b/arch/microblaze/include/asm/prom.h
index 20f7b3a926e8..37e6f305a68e 100644
--- a/arch/microblaze/include/asm/prom.h
+++ b/arch/microblaze/include/asm/prom.h
@@ -16,6 +16,18 @@
 #define _ASM_MICROBLAZE_PROM_H
 #ifdef __KERNEL__
 
+/* Definitions used by the flattened device tree */
+#define OF_DT_HEADER            0xd00dfeed /* marker */
+#define OF_DT_BEGIN_NODE        0x1 /* Start of node, full name */
+#define OF_DT_END_NODE          0x2 /* End node */
+#define OF_DT_PROP              0x3 /* Property: name off, size, content */
+#define OF_DT_NOP               0x4 /* nop */
+#define OF_DT_END               0x9
+
+#define OF_DT_VERSION           0x10
+
+#ifndef __ASSEMBLY__
+
 #include <linux/types.h>
 #include <linux/proc_fs.h>
 #include <linux/platform_device.h>
@@ -29,16 +41,6 @@
 #define of_prop_cmp(s1, s2)             strcmp((s1), (s2))
 #define of_node_cmp(s1, s2)             strcasecmp((s1), (s2))
 
-/* Definitions used by the flattened device tree */
-#define OF_DT_HEADER            0xd00dfeed /* marker */
-#define OF_DT_BEGIN_NODE        0x1 /* Start of node, full name */
-#define OF_DT_END_NODE          0x2 /* End node */
-#define OF_DT_PROP              0x3 /* Property: name off, size, content */
-#define OF_DT_NOP               0x4 /* nop */
-#define OF_DT_END               0x9
-
-#define OF_DT_VERSION           0x10
-
 /*
  * This is what gets passed to the kernel by prom_init or kexec
  *
@@ -309,5 +311,6 @@ extern void __iomem *of_iomap(struct device_node *device, int index);
  */
 #include <linux/of.h>
 
+#endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_MICROBLAZE_PROM_H */
diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S
index e568d6ec621b..815bcaae99c3 100644
--- a/arch/microblaze/kernel/head.S
+++ b/arch/microblaze/kernel/head.S
@@ -31,6 +31,7 @@
 #include <linux/linkage.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
+#include <asm/prom.h>           /* for OF_DT_HEADER */
 
 #ifdef CONFIG_MMU
 #include <asm/setup.h> /* COMMAND_LINE_SIZE */
@@ -54,11 +55,16 @@ ENTRY(_start)
         andi    r1, r1, ~2
         mts     rmsr, r1
 
-/* save fdt to kernel location */
-/* r7 stores pointer to fdt blob */
-        beqi    r7, no_fdt_arg
+/* r7 may point to an FDT, or there may be one linked in.
+   if it's in r7, we've got to save it away ASAP.
+   We ensure r7 points to a valid FDT, just in case the bootloader
+   is broken or non-existent */
+        beqi    r7, no_fdt_arg                  /* NULL pointer?  don't copy */
+        lw      r11, r0, r7                     /* Does r7 point to a */
+        rsubi   r11, r11, OF_DT_HEADER          /* valid FDT? */
+        bnei    r11, no_fdt_arg                 /* No - get out of here */
         or      r11, r0, r0 /* incremment */
-        ori     r4, r0, TOPHYS(_fdt_start) /* save bram context */
+        ori     r4, r0, TOPHYS(_fdt_start)
         ori     r3, r0, (0x4000 - 4)
 _copy_fdt:
         lw      r12, r7, r11 /* r12 = r7 + r11 */
@@ -67,6 +73,7 @@ _copy_fdt:
         bgtid   r3, _copy_fdt /* loop for all entries */
         addik   r3, r3, -4 /* descrement loop */
 no_fdt_arg:
+        add     r7, r0, r0                      /* Clear r7, just to be sure */
 
 #ifdef CONFIG_MMU
 
diff --git a/arch/microblaze/kernel/setup.c b/arch/microblaze/kernel/setup.c
index 8709bea09604..59a383621b22 100644
--- a/arch/microblaze/kernel/setup.c
+++ b/arch/microblaze/kernel/setup.c
@@ -139,7 +139,8 @@ void __init machine_early_init(const char *cmdline, unsigned int ram,
 #endif
 
         early_printk("Ramdisk addr 0x%08x, FDT 0x%08x\n", ram, fdt);
-        printk(KERN_NOTICE "Found FDT at 0x%08x\n", fdt);
+        if(fdt)
+                printk(KERN_NOTICE "Found FDT at 0x%08x\n", fdt);
 
 #ifdef CONFIG_MTD_UCLINUX
         early_printk("Found romfs @ 0x%08x (0x%08x)\n",