microblaze: Fix DTB passing from bootloader

Little endian system needs to check OF_DT_HEADER
but it is swapped because it is in big-endian.
Microblaze LE provides lwr instruction which loads
magic number in BIG endian format which can be compared.

There is used the fact that if you write 0x1 as word
and load it as byte then you get for big-endian zero
and 1 for little-endian.

Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 12 insertions, 2 deletions

diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S
index 42434008209e..0db20b5abb54 100644
--- a/arch/microblaze/kernel/head.S
+++ b/arch/microblaze/kernel/head.S
@@ -77,8 +77,18 @@ real_start:
    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? */
+/* Does r7 point to a valid FDT? Load HEADER magic number */
+        /* Run time Big/Little endian platform */
+        /* Save 1 as word and load byte - 0 - BIG, 1 - LITTLE */
+        addik   r11, r0, 0x1 /* BIG/LITTLE checking value */
+        /* __bss_start will be zeroed later - it is just temp location */
+        swi     r11, r0, TOPHYS(__bss_start)
+        lbui    r11, r0, TOPHYS(__bss_start)
+        beqid   r11, big_endian /* DO NOT break delay stop dependency */
+        lw      r11, r0, r7 /* Big endian load in delay slot */
+        lwr     r11, r0, r7 /* Little endian load */
+big_endian:
+        rsubi   r11, r11, OF_DT_HEADER  /* Check FDT header */
         beqi    r11, _prepare_copy_fdt
         or      r7, r0, r0              /* clear R7 when not valid DTB */
         bnei    r11, no_fdt_arg                 /* No - get out of here */