arm: arm926ej-s: start.S: port save_boot_params support from armv7 code

The ARMv7 start code has support for saving some boot params at the
entry point, which is used by some SoCs to return to BROM.

Port this to ARM926EJ-S start code.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

diff --git a/arch/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
index 0afcc47..aca7793 100644 (file)
--- a/arch/arm/cpu/arm926ejs/start.S
+++ b/arch/arm/cpu/arm926ejs/start.S
@@ -17,6 +17,7 @@
 #include <asm-offsets.h>
 #include <config.h>
 #include <common.h>
+#include <linux/linkage.h>
 
 /*
  *************************************************************************
@@ -32,8 +33,13 @@
  */
 
        .globl  reset
+       .globl  save_boot_params_ret
+       .type   save_boot_params_ret,%function
 
 reset:
+       /* Allow the board to save important registers */
+       b       save_boot_params
+save_boot_params_ret:
        /*
         * set the cpu to SVC32 mode
         */
@@ -110,3 +116,16 @@ flush_dcache:
 #endif
        mov     pc, lr          /* back to my caller */
 #endif /* CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT) */
+
+/*************************************************************************
+ *
+ * void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3)
+ *     __attribute__((weak));
+ *
+ * Stack pointer is not yet initialized at this moment
+ * Don't save anything to stack even if compiled with -O0
+ *
+ *************************************************************************/
+WEAK(save_boot_params)
+       b       save_boot_params_ret    /* back to my caller */
+ENDPROC(save_boot_params)