[PATCH] ARM: stm32: Power cycle Buck3 in reset on DHSOM

[Marek Vasut]

In case the DHSOM is in suspend state and either reset button is pushed
or IWDG2 triggers a watchdog reset, then DRAM initialization could fail
as follows:

  "
  RAM: DDR3L 32bits 2x4Gb 533MHz
  DDR invalid size : 0x4, expected 0x40000000
  DRAM init failed: -22
  ### ERROR ### Please RESET the board ###
  "

Avoid this failure by not keeping any Buck regulators enabled during reset,
let the SoC and DRAMs power cycle fully. Since the change which keeps Buck3
VDD enabled during reset is ST specific, move this addition to ST specific
SPL board initialization so that it wouldn't affect the DHSOM .

Signed-off-by: Marek Vasut <marex at denx.de>
---
NOTE: This is 2023.07 material
NOTE: d1a4b09de64 ("board: st: stpmic1: add function stpmic1_init")
      mentions 'keep vdd on during the reset cycle (to avoid issue
      when backup battery is absent)', but there is no further
      description of the 'issue'. Can you please elaborate ?
---
Cc: Patrice Chotard <patrice.chotard at foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay at foss.st.com>
Cc: uboot-stm32 at st-md-mailman.stormreply.com
---
 board/st/common/stpmic1.c | 10 +++-------
 board/st/common/stpmic1.h |  2 +-
 board/st/stm32mp1/spl.c   | 13 +++++++++++--
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/board/st/common/stpmic1.c b/board/st/common/stpmic1.c
index d52dce4f657..969ad484864 100644
--- a/board/st/common/stpmic1.c
+++ b/board/st/common/stpmic1.c
@@ -185,21 +185,17 @@ static int stmpic_buck1_set(struct udevice *dev, u32 voltage_mv)
 }
 
 /* early init of PMIC */
-void stpmic1_init(u32 voltage_mv)
+struct udevice *stpmic1_init(u32 voltage_mv)
 {
 	struct udevice *dev;
 
 	if (uclass_get_device_by_driver(UCLASS_PMIC,
 					DM_DRIVER_GET(pmic_stpmic1), &dev))
-		return;
+		return NULL;
 
 	/* update VDDCORE = BUCK1 */
 	if (voltage_mv)
 		stmpic_buck1_set(dev, voltage_mv);
 
-	/* Keep vdd on during the reset cycle */
-	pmic_clrsetbits(dev,
-			STPMIC1_BUCKS_MRST_CR,
-			STPMIC1_MRST_BUCK(STPMIC1_BUCK3),
-			STPMIC1_MRST_BUCK(STPMIC1_BUCK3));
+	return dev;
 }
diff --git a/board/st/common/stpmic1.h b/board/st/common/stpmic1.h
index b17d6f16338..7a7169d7cea 100644
--- a/board/st/common/stpmic1.h
+++ b/board/st/common/stpmic1.h
@@ -3,4 +3,4 @@
  * Copyright (C) 2020, STMicroelectronics - All Rights Reserved
  */
 
-void stpmic1_init(u32 voltage_mv);
+struct udevice *stpmic1_init(u32 voltage_mv);
diff --git a/board/st/stm32mp1/spl.c b/board/st/stm32mp1/spl.c
index 747ec7e445a..8b4a529f759 100644
--- a/board/st/stm32mp1/spl.c
+++ b/board/st/stm32mp1/spl.c
@@ -5,6 +5,8 @@
 
 #include <config.h>
 #include <common.h>
+#include <power/pmic.h>
+#include <power/stpmic1.h>
 #include <asm/arch/sys_proto.h>
 #include "../common/stpmic1.h"
 
@@ -19,8 +21,15 @@ void board_vddcore_init(u32 voltage_mv)
 
 int board_early_init_f(void)
 {
-	if (IS_ENABLED(CONFIG_PMIC_STPMIC1) && CONFIG_IS_ENABLED(POWER))
-		stpmic1_init(opp_voltage_mv);
+	if (IS_ENABLED(CONFIG_PMIC_STPMIC1) && CONFIG_IS_ENABLED(POWER)) {
+		struct udevice *dev = stpmic1_init(opp_voltage_mv);
+
+		/* Keep vdd on during the reset cycle */
+		pmic_clrsetbits(dev,
+				STPMIC1_BUCKS_MRST_CR,
+				STPMIC1_MRST_BUCK(STPMIC1_BUCK3),
+				STPMIC1_MRST_BUCK(STPMIC1_BUCK3));
+	}
 
 	return 0;
 }
-- 
2.39.2