arm: armv8: Improve SPL data save and restore implementation

Introduce a new symbol in the beginning of .data section in
the common ARMv8 linker script and use that as a reference
for data save and restore.

Previously, the code would rely on calculating the start of
the .data section address via data size, however, we observed
that the data size does not really reflect the SPL mapped
addresses.

In our case, the binman_sym section size was not included in
the data size, which will result in a wrong address for the
.data start section, which prevents us from properly saving
and restoring SPL data.

This approach skips the calculation for the starting address
of the .data section, and instead just defines the beginning
address of the .data section and calling the symbol as needed,
in which we think as a simpler and much more robust method.

Signed-off-by: Alif Zakuan Yuslaimi <alif.zakuan.yuslaimi@altera.com>
Signed-off-by: Tien Fong Chee <tien.fong.chee@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@altera.com>

arch/arm/cpu/armv8/spl_data.c

@@ -5,23 +5,28 @@
 
 #include <spl.h>
 
+char __data_start[0] __section(".__data_start");
 char __data_save_start[0] __section(".__data_save_start");
 char __data_save_end[0] __section(".__data_save_end");
 
 u32 cold_reboot_flag = 1;
 
+u32 __weak reset_flag(void)
+{
+	return 1;
+}
+
 void spl_save_restore_data(void)
 {
 	u32 data_size = __data_save_end - __data_save_start;
+	cold_reboot_flag = reset_flag();
 
 	if (cold_reboot_flag == 1) {
 		/* Save data section to data_save section */
-		memcpy(__data_save_start, __data_save_start - data_size,
-		       data_size);
+		memcpy(__data_save_start, __data_start, data_size);
 	} else {
 		/* Restore the data_save section to data section */
-		memcpy(__data_save_start - data_size, __data_save_start,
-		       data_size);
+		memcpy(__data_start, __data_save_start, data_size);
 	}
 
 	cold_reboot_flag++;

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

@@ -37,6 +37,7 @@ SECTIONS
 
 	.data : {
 		. = ALIGN(8);
+		*(.__data_start)
 		*(.data*)
 	} >.sram
 

arch/arm/mach-socfpga/spl_agilex5.c

@@ -21,11 +21,32 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+u32 reset_flag(void)
+{
+	/* Check rstmgr.stat for warm reset status */
+	u32 status = readl(SOCFPGA_RSTMGR_ADDRESS);
+
+	/* Check whether any L4 watchdogs or SDM had triggered warm reset */
+	u32 warm_reset_mask = RSTMGR_L4WD_MPU_WARMRESET_MASK;
+
+	if (status & warm_reset_mask)
+		return 0;
+
+	return 1;
+}
+
 void board_init_f(ulong dummy)
 {
 	int ret;
 	struct udevice *dev;
 
+	/* Enable Async */
+	asm volatile("msr daifclr, #4");
+
+#ifdef CONFIG_SPL_BUILD
+	spl_save_restore_data();
+#endif
+
 	ret = spl_early_init();
 	if (ret)
 		hang();

configs/socfpga_agilex5_defconfig

@@ -97,3 +97,4 @@ CONFIG_BLOBLIST=y
 CONFIG_BLOBLIST_SIZE=0x1000
 CONFIG_BLOBLIST_ADDR=0x7e000
 CONFIG_HANDOFF=y
+CONFIG_SPL_RECOVER_DATA_SECTION=y