[PATCH v2 21/26] arm: armv8: Improve SPL data save and restore implementation

[Chee, Tien Fong]

-----Original Message-----
From: alif.zakuan.yuslaimi at intel.com <alif.zakuan.yuslaimi at intel.com> 
Sent: Tuesday, February 18, 2025 4:35 PM
To: u-boot at lists.denx.de
Cc: Marek Vasut <marex at denx.de>; Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>; Chee, Tien Fong <tien.fong.chee at altera.com>; Yuslaimi, Alif Zakuan <alif.zakuan.yuslaimi at altera.com>; Meng, Tingting <tingting.meng at altera.com>; Ng, Boon Khai <boon.khai.ng at altera.com>; Hea, Kok Kiang <kok.kiang.hea at altera.com>; Alif Zakuan Yuslaimi <alif.zakuan.yuslaimi at intel.com>
Subject: [PATCH v2 21/26] arm: armv8: Improve SPL data save and restore implementation

From: Alif Zakuan Yuslaimi <alif.zakuan.yuslaimi at intel.com>

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 at altera.com>
Signed-off-by: Tien Fong Chee <tien.fong.chee at altera.com>

---

v1->v2
- Use common ARMv8 start.S script, introduce new symbol to
  preserve Agilex5 warm reset behaviour
---
 arch/arm/cpu/armv8/spl_data.c       | 13 +++++++++----
 arch/arm/cpu/armv8/u-boot-spl.lds   |  1 +
 arch/arm/mach-socfpga/spl_agilex5.c | 21 +++++++++++++++++++++
 configs/socfpga_agilex5_defconfig   |  1 +
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/arch/arm/cpu/armv8/spl_data.c b/arch/arm/cpu/armv8/spl_data.c index 259b49ff364..492353c93df 100644
--- a/arch/arm/cpu/armv8/spl_data.c
+++ b/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++;
diff --git a/arch/arm/cpu/armv8/u-boot-spl.lds b/arch/arm/cpu/armv8/u-boot-spl.lds
index fed69644b55..c4f83ec9cfc 100644
--- a/arch/arm/cpu/armv8/u-boot-spl.lds
+++ b/arch/arm/cpu/armv8/u-boot-spl.lds
@@ -37,6 +37,7 @@ SECTIONS
 
 	.data : {
 		. = ALIGN(8);
+		*(.__data_start)
 		*(.data*)
 	} >.sram
 
diff --git a/arch/arm/mach-socfpga/spl_agilex5.c b/arch/arm/mach-socfpga/spl_agilex5.c
index c87e9ed1641..3451611082d 100644
--- a/arch/arm/mach-socfpga/spl_agilex5.c
+++ b/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();
diff --git a/configs/socfpga_agilex5_defconfig b/configs/socfpga_agilex5_defconfig
index 10686a0a7b3..61ce065a2bf 100644
--- a/configs/socfpga_agilex5_defconfig
+++ b/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
--
2.25.1

Reviewed-by: Tien Fong Chee <tien.fong.chee at altera.com>

Best regards,
Tien Fong