[U-Boot] [PATCH v2 2/5] rockchip: back-to-bootrom: replace assembly-implementation with C-code

Philipp Tomsich
2017-09-18T18:18:25Z

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 <philipp.tomsich@theobroma-systems.com>
---

Changes in v2: None

arch/arm/include/asm/arch-rockchip/bootrom.h | 27 ++++++++---
arch/arm/mach-rockchip/Makefile | 4 +-
arch/arm/mach-rockchip/bootrom.c | 52 ++++++++++++++++++++-
arch/arm/mach-rockchip/save_boot_param.S | 69 ----------------------------
4 files changed, 73 insertions(+), 79 deletions(-)
delete mode 100644 arch/arm/mach-rockchip/save_boot_param.S

diff --git a/arch/arm/include/asm/arch-rockchip/bootrom.h b/arch/arm/include/asm/arch-rockchip/bootrom.h
index 169cc5e..2f61a33 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 <heiko@sntech.de>
+ * (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
diff --git a/arch/arm/mach-rockchip/Makefile b/arch/arm/mach-rockchip/Makefile
index 79e9704..f8b23ea 100644
--- a/arch/arm/mach-rockchip/Makefile
+++ b/arch/arm/mach-rockchip/Makefile
@@ -8,8 +8,8 @@
# this may have entered from ATF with the stack-pointer pointing to
# inaccessible/protected memory (and the bootrom-helper assumes that
# the stack-pointer is valid before switching to the U-Boot stack).
-obj-spl-$(CONFIG_ROCKCHIP_BROM_HELPER) += bootrom.o save_boot_param.o
-obj-tpl-$(CONFIG_ROCKCHIP_BROM_HELPER) += bootrom.o save_boot_param.o
+obj-spl-$(CONFIG_ROCKCHIP_BROM_HELPER) += bootrom.o
+obj-tpl-$(CONFIG_ROCKCHIP_BROM_HELPER) += bootrom.o

obj-tpl-$(CONFIG_ROCKCHIP_RK3188) += rk3188-board-tpl.o
obj-tpl-$(CONFIG_ROCKCHIP_RK3368) += rk3368-board-tpl.o
diff --git a/arch/arm/mach-rockchip/bootrom.c b/arch/arm/mach-rockchip/bootrom.c
index 8380e4e..7b9b307 100644
--- a/arch/arm/mach-rockchip/bootrom.c
+++ b/arch/arm/mach-rockchip/bootrom.c
@@ -6,11 +6,61 @@

#include <common.h>
#include <asm/arch/bootrom.h>
+#include <asm/setjmp.h>
+#include <asm/system.h>
+
+/*
+ * Force the jmp_buf to the data-section, as .bss will not be valid
+ * when save_boot_params is invoked.
+ */
+static jmp_buf brom_ctx __section(".data");

void back_to_bootrom(void)
{
#if CONFIG_IS_ENABLED(LIBCOMMON_SUPPORT)
puts("Returning to boot ROM...\n");
#endif
- _back_to_bootrom_s();
+ longjmp(brom_ctx, BROM_BOOT_NEXTSTAGE);
+}
+
+/*
+ * All Rockchip BROM implementations enter with a valid stack-pointer,
+ * so this can safely be implemented in C (providing a single
+ * implementation both for ARMv7 and AArch64).
+ */
+int save_boot_params(void)
+{
+ int ret = setjmp(brom_ctx);
+
+ switch (ret) {
+ case 0:
+ /*
+ * This is the initial pass through this function
+ * (i.e. saving the context), setjmp just setup up the
+ * brom_ctx: transfer back into the startup-code at
+ * 'save_boot_params_ret' and let the compiler know
+ * that this will not return.
+ */
+ save_boot_params_ret();
+ while (true)
+ /* does not return */;
+ break;
+
+ case BROM_BOOT_NEXTSTAGE:
+ /*
+ * To instruct the BROM to boot the next stage, we
+ * need to return 0 to it: i.e. we need to rewrite
+ * the return code once more.
+ */
+ ret = 0;
+ break;
+
+ default:
+#if CONFIG_IS_ENABLED(LIBCOMMON_SUPPORT)
+ puts("FATAL: unexpected command to back_to_bootrom()\n");
+#endif
+ hang();
+ };
+
+ return ret;
}
diff --git a/arch/arm/mach-rockchip/save_boot_param.S b/arch/arm/mach-rockchip/save_boot_param.S
deleted file mode 100644
index 50fce20..0000000
--- a/arch/arm/mach-rockchip/save_boot_param.S
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * (C) Copyright 2016 Rockchip Electronics Co., Ltd
- * (C) Copyright 2017 Theobroma Systems Design und Consulting GmbH
- *
- * SPDX-License-Identifier: GPL-2.0+
- */
-
-#include <linux/linkage.h>
-
-#if defined(CONFIG_ARM64)
-.globl SAVE_SP_ADDR
-SAVE_SP_ADDR:
- .quad 0
-
-ENTRY(save_boot_params)
- sub sp, sp, #0x60
- stp x29, x30, [sp, #0x50]
- stp x27, x28, [sp, #0x40]
- stp x25, x26, [sp, #0x30]
- stp x23, x24, [sp, #0x20]
- stp x21, x22, [sp, #0x10]
- stp x19, x20, [sp, #0]
- ldr x8, =SAVE_SP_ADDR
- mov x9, sp
- str x9, [x8]
- b save_boot_params_ret /* back to my caller */
-ENDPROC(save_boot_params)
-
-.globl _back_to_bootrom_s
-ENTRY(_back_to_bootrom_s)
- ldr x0, =SAVE_SP_ADDR
- ldr x0, [x0]
- mov sp, x0
- ldp x29, x30, [sp, #0x50]
- ldp x27, x28, [sp, #0x40]
- ldp x25, x26, [sp, #0x30]
- ldp x23, x24, [sp, #0x20]
- ldp x21, x22, [sp, #0x10]
- ldp x19, x20, [sp]
- add sp, sp, #0x60
- mov x0, xzr
- ret
-ENDPROC(_back_to_bootrom_s)
-#else
-.globl SAVE_SP_ADDR
-SAVE_SP_ADDR:
- .word 0
-
-/*
- * void save_boot_params
- *
- * Save sp, lr, r1~r12
- */
-ENTRY(save_boot_params)
- push {r1-r12, lr}
- ldr r0, =SAVE_SP_ADDR
- str sp, [r0]
- b save_boot_params_ret @ back to my caller
-ENDPROC(save_boot_params)
-
-
-.globl _back_to_bootrom_s
-ENTRY(_back_to_bootrom_s)
- ldr r0, =SAVE_SP_ADDR
- ldr sp, [r0]
- mov r0, #0
- pop {r1-r12, pc}
-ENDPROC(_back_to_bootrom_s)
-#endif
--
2.1.4