openrisc: enable passing of flattened device tree pointer
This patch enables passing a fdt pointer to the kernel.
This makes for the kernel parameter API:
void kernel(unsigned int fdt);
which, in accordance with the OpenRISC ABI results in:
r3 = pointer to fdt
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Signed-off-by: Jonas Bonn <jonas@southpole.se>
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index c75018d..1088b5f 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -26,6 +26,7 @@
#include <asm/cache.h>
#include <asm/spr_defs.h>
#include <asm/asm-offsets.h>
+#include <linux/of_fdt.h>
#define tophys(rd,rs) \
l.movhi rd,hi(-KERNELBASE) ;\
@@ -440,6 +441,9 @@
__HEAD
.global _start
_start:
+ /* save kernel parameters */
+ l.or r25,r0,r3 /* pointer to fdt */
+
/*
* ensure a deterministic start
*/
@@ -471,7 +475,6 @@
CLEAR_GPR(r22)
CLEAR_GPR(r23)
CLEAR_GPR(r24)
- CLEAR_GPR(r25)
CLEAR_GPR(r26)
CLEAR_GPR(r27)
CLEAR_GPR(r28)
@@ -565,6 +568,18 @@
// reset the simulation counters
l.nop 5
+ /* check fdt header magic word */
+ l.lwz r3,0(r25) /* load magic from fdt into r3 */
+ l.movhi r4,hi(OF_DT_HEADER)
+ l.ori r4,r4,lo(OF_DT_HEADER)
+ l.sfeq r3,r4
+ l.bf _fdt_found
+ l.nop
+ /* magic number mismatch, set fdt pointer to null */
+ l.or r25,r0,r0
+_fdt_found:
+ /* pass fdt pointer to or32_early_setup in r3 */
+ l.or r3,r0,r25
LOAD_SYMBOL_2_GPR(r24, or32_early_setup)
l.jalr r24
l.nop