rockchip: back-to-bootrom: replace assembly-implementation with C-code

The back-to-bootrom implementation for Rockchip has always relied on
the stack-pointer being valid on entry, so there was little reason to
have this as an assembly implementation.

This provides a new C-only implementation of save_boot_params and
back_to_bootrom (relying on setjmp/longjmp) and removes the older
assembly-only implementation.

Signed-off-by: Philipp Tomsich <[email protected]>
Tested-by: Andy Yan <[email protected]>

1 files changed, 20 insertions, 7 deletions

diff --git a/arch/arm/include/asm/arch-rockchip/bootrom.h b/arch/arm/include/asm/arch-rockchip/bootrom.h
index 169cc5e50b0..2f61a338116 100644
--- a/arch/arm/include/asm/arch-rockchip/bootrom.h
+++ b/arch/arm/include/asm/arch-rockchip/bootrom.h
@@ -1,5 +1,6 @@
 /*
  * (C) Copyright 2017 Heiko Stuebner <[email protected]>
+ * (C) Copyright 2017 Theobroma Systems Design und Consulting GmbH
  *
  * SPDX-License-Identifier:	GPL-2.0
  */
@@ -14,15 +15,27 @@
 extern u32 SAVE_SP_ADDR;
 
 /**
- * Hand control back to the bootrom to load another
- * boot stage.
+ * back_to_bootrom() - return to bootrom (for TPL/SPL), passing a
+ *                     result code
+ *
+ * Transfer control back to the Rockchip BROM, restoring necessary
+ * register context and passing a command/result code to the BROM
+ * to instruct its next actions (e.g. continue boot sequence, enter
+ * download mode, ...).
+ *
+ * This function does not return.
  */
-void back_to_bootrom(void);
+enum rockchip_bootrom_cmd {
+	/*
+	 * These can not start at 0, as 0 has a special meaning
+	 * for setjmp().
+	 */
 
-/**
- * Assembler component for the above (do not call this directly)
- */
-void _back_to_bootrom_s(void);
+	BROM_BOOT_NEXTSTAGE = 1,  /* continue boot-sequence */
+	BROM_BOOT_ENTER_DNL,      /* have BROM enter download-mode */
+};
+
+void back_to_bootrom(void);
 
 /**
  * Boot-device identifiers as used by the BROM