imx: imx8qm/qxp: Recover SPL data section for partition reboot

When doing partition reboot, the boot image won't be reloaded by ROM,
it is just CPU reset to boot entry. The SW has to keep the boot image
inside the RAM unchanged. It includes both the TEXT section and DATA
section.

For SPL, the problem is DATA section will be updated at runtime, so in
next partition reboot the data is not same as the initial value from
cold boot. If any code depends on the initial value, then it will have
problem.

This patch introduces a mechanism to recover the data section
for partition reboot. It adds a new section in image for saving
data section. When from cold boot, the data section will be saved
to that new section at SPL early phase. When from partition reboot,
the data section will be restored from the new section.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>

arch/arm/cpu/armv8/Kconfig

@@ -76,6 +76,12 @@ config SPL_ARMV8_SEC_FIRMWARE_SUPPORT
 	help
 	  Say Y here to support this framework in SPL phase.
 
+config SPL_RECOVER_DATA_SECTION
+	bool "save/restore SPL data section"
+	help
+	  Say Y here to save SPL data section for cold boot, and restore
+	  at warm boot in SPL phase.
+
 config SEC_FIRMWARE_ARMV8_PSCI
 	bool "PSCI implementation in secure monitor firmware"
 	depends on ARMV8_SEC_FIRMWARE_SUPPORT || SPL_ARMV8_SEC_FIRMWARE_SUPPORT

arch/arm/cpu/armv8/Makefile

@@ -30,6 +30,10 @@ obj-$(CONFIG_ARMV8_SPIN_TABLE) += spin_table.o spin_table_v8.o
 endif
 obj-$(CONFIG_$(SPL_)ARMV8_SEC_FIRMWARE_SUPPORT) += sec_firmware.o sec_firmware_asm.o
 
+ifdef CONFIG_SPL_BUILD
+obj-$(CONFIG_SPL_RECOVER_DATA_SECTION) += spl_data.o
+endif
+
 obj-$(CONFIG_FSL_LAYERSCAPE) += fsl-layerscape/
 obj-$(CONFIG_S32V234) += s32v234/
 obj-$(CONFIG_TARGET_HIKEY) += hisilicon/

arch/arm/cpu/armv8/spl_data.c

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2020 NXP
+ */
+
+#include <common.h>
+#include <spl.h>
+
+char __data_save_start[0] __section(.__data_save_start);
+char __data_save_end[0] __section(.__data_save_end);
+
+u32 cold_reboot_flag = 1;
+
+void spl_save_restore_data(void)
+{
+	u32 data_size = __data_save_end - __data_save_start;
+
+	if (cold_reboot_flag == 1) {
+		/* Save data section to data_save section */
+		memcpy(__data_save_start, __data_save_start - data_size,
+		       data_size);
+	} else {
+		/* Restore the data_save section to data section */
+		memcpy(__data_save_start - data_size, __data_save_start,
+		       data_size);
+	}
+
+	cold_reboot_flag++;
+}

arch/arm/cpu/armv8/u-boot-spl.lds

@@ -38,6 +38,14 @@ SECTIONS
 		*(.data*)
 	} >.sram
 
+#ifdef CONFIG_SPL_RECOVER_DATA_SECTION
+	.data_save : {
+		*(.__data_save_start)
+		. = SIZEOF(.data);
+		*(.__data_save_end)
+	} >.sram
+#endif
+
 	.u_boot_list : {
 		. = ALIGN(8);
 		KEEP(*(SORT(.u_boot_list*)));

arch/arm/mach-imx/imx8/Kconfig

@@ -18,11 +18,13 @@ config MU_BASE_SPL
 config IMX8QM
 	select IMX8
 	select SUPPORT_SPL
+	select SPL_RECOVER_DATA_SECTION
 	bool
 
 config IMX8QXP
 	select IMX8
 	select SUPPORT_SPL
+	select SPL_RECOVER_DATA_SECTION
 	bool
 
 config SYS_SOC

arch/arm/mach-imx/imx8/cpu.c

@@ -13,6 +13,7 @@
 #include <dm/lists.h>
 #include <dm/uclass.h>
 #include <errno.h>
+#include <spl.h>
 #include <thermal.h>
 #include <asm/arch/sci/sci.h>
 #include <asm/arch/sys_proto.h>
@@ -39,6 +40,10 @@ struct pass_over_info_t *get_pass_over_info(void)
 
 int arch_cpu_init(void)
 {
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_RECOVER_DATA_SECTION)
+	spl_save_restore_data();
+#endif
+
 #ifdef CONFIG_SPL_BUILD
 	struct pass_over_info_t *pass_over;
 

include/spl.h

@@ -582,4 +582,5 @@ void spl_perform_fixups(struct spl_image_info *spl_image);
  */
 struct image_header *spl_get_load_buffer(ssize_t offset, size_t size);
 
+void spl_save_restore_data(void);
 #endif