[PATCH] powerpc: Add back support for booting from BootX (#2)

ARCH=powerpc couldn't boot from BootX as it uses a "different" way of
getting in the kernel. This patch adds the necessary trampolines,
creating a flattened device-tree from the tree passed from MacOS, and
initializing the btext engine early for really-early debugging.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index fdd34dbd8797..6359e364fe66 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -125,6 +125,19 @@ __start:
         bl      prom_init
         trap
 
+/*
+ * Check for BootX signature when supporting PowerMac and branch to
+ * appropriate trampoline if it's present
+ */
+#ifdef CONFIG_PPC_PMAC
+1:      lis     r31,0x426f
+        ori     r31,r31,0x6f58
+        cmpw    0,r3,r31
+        bne     1f
+        bl      bootx_init
+        trap
+#endif /* CONFIG_PPC_PMAC */
+
 1:      mr      r31,r3                  /* save parameters */
         mr      r30,r4
         li      r24,0                   /* cpu # */