wdt: imx8qxp: add option to control external PMIC wdt via IMX8 SCU

Driver for a PMIC watchdog timer controlled via Siemens SCU firmware
extensions. Only useful on some Siemens i.MX8-based platforms as
special SCFW is needed which provides the needed SCU API.

Signed-off-by: Andrej Valek <andrej.valek@siemens.com>
Signed-off-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/misc/imx8/scu_api.c

@@ -951,6 +951,26 @@ int sc_timer_set_wdog_window(sc_ipc_t ipc, sc_timer_wdog_time_t window)
 	return ret;
 }
 
+int sc_timer_control_siemens_pmic_wdog(sc_ipc_t ipc, u8 cmd)
+{
+	struct udevice *dev = gd->arch.scu_dev;
+	struct sc_rpc_msg_s msg;
+	int size = sizeof(struct sc_rpc_msg_s);
+	int ret;
+
+	RPC_VER(&msg) = SC_RPC_VERSION;
+	RPC_SVC(&msg) = (u8)SC_RPC_SVC_TIMER;
+	RPC_FUNC(&msg) = (u8)TIMER_FUNC_CTRL_SIEMENS_PMIC_WDOG;
+	RPC_U8(&msg, 0U) = (u8)cmd;
+	RPC_SIZE(&msg) = 2U;
+
+	ret = misc_call(dev, SC_FALSE, &msg, size, &msg, size);
+	if (ret)
+		printf("%s: res:%d\n", __func__, RPC_R8(&msg));
+
+	return ret;
+}
+
 int sc_seco_authenticate(sc_ipc_t ipc, sc_seco_auth_cmd_t cmd,
 			 sc_faddr_t addr)
 {

drivers/watchdog/Kconfig

@@ -351,6 +351,13 @@ config WDT_SBSA
 	   In the single stage mode, when the timeout is reached, your system
 	   will be reset by WS1. The first signal (WS0) is ignored.
 
+config WDT_SIEMENS_PMIC
+	bool "Enable PMIC Watchdog Timer support for Siemens platforms"
+	depends on ARCH_IMX8 && WDT
+	help
+	  Select this to enable the PMIC watchdog driver controlled via
+	  IMX8 SCU API found on Siemens platforms.
+
 config WDT_SL28CPLD
 	bool "sl28cpld watchdog timer support"
 	depends on WDT && SL28CPLD

drivers/watchdog/Makefile

@@ -45,6 +45,7 @@ obj-$(CONFIG_WDT_OCTEONTX) += octeontx_wdt.o
 obj-$(CONFIG_WDT_OMAP3) += omap_wdt.o
 obj-$(CONFIG_WDT_SBSA) += sbsa_gwdt.o
 obj-$(CONFIG_WDT_K3_RTI) += rti_wdt.o
+obj-$(CONFIG_WDT_SIEMENS_PMIC) += siemens_pmic_wdt.o
 obj-$(CONFIG_WDT_SL28CPLD) += sl28cpld-wdt.o
 obj-$(CONFIG_WDT_SP805) += sp805_wdt.o
 obj-$(CONFIG_WDT_STARFIVE) += starfive_wdt.o

drivers/watchdog/siemens_pmic_wdt.c

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for a PMIC watchdog timer controlled via Siemens SCU firmware
+ * extensions. Only useful on some Siemens i.MX8-based platforms as
+ * special NXP SCFW is needed which provides the needed SCU API.
+ *
+ * Copyright (C) 2024 Siemens AG
+ */
+
+#include <dm.h>
+#include <wdt.h>
+#include <firmware/imx/sci/sci.h>
+
+/* watchdog commands */
+#define CMD_START_WDT 0x55
+#define CMD_STOP_WDT  0x45
+#define CMD_PING_WDT  0x35
+
+static int scu_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+	/* start external watchdog via Timer API */
+	return sc_timer_control_siemens_pmic_wdog(-1, CMD_START_WDT);
+}
+
+static int scu_wdt_stop(struct udevice *dev)
+{
+	/* stop external watchdog via Timer API */
+	return sc_timer_control_siemens_pmic_wdog(-1, CMD_STOP_WDT);
+}
+
+static int scu_wdt_reset(struct udevice *dev)
+{
+	return sc_timer_control_siemens_pmic_wdog(-1, CMD_PING_WDT);
+}
+
+static int scu_wdt_probe(struct udevice *dev)
+{
+	debug("%s(dev=%p)\n", __func__, dev);
+	return 0;
+}
+
+static const struct wdt_ops scu_wdt_ops = {
+	.reset		= scu_wdt_reset,
+	.start		= scu_wdt_start,
+	.stop		= scu_wdt_stop,
+};
+
+static const struct udevice_id scu_wdt_ids[] = {
+	{ .compatible = "siemens,scu-wdt" },
+	{ }
+};
+
+U_BOOT_DRIVER(scu_wdt) = {
+	.name		= "scu_wdt",
+	.id		= UCLASS_WDT,
+	.of_match	= scu_wdt_ids,
+	.probe		= scu_wdt_probe,
+	.ops		= &scu_wdt_ops,
+};

include/firmware/imx/sci/rpc.h

@@ -231,4 +231,7 @@ struct sc_rpc_msg_s {
 #define TIMER_FUNC_SET_SYSCTR_PERIODIC_ALARM 17U /* Index for sc_timer_set_sysctr_periodic_alarm() RPC call */
 #define TIMER_FUNC_CANCEL_SYSCTR_ALARM 18U /* Index for sc_timer_cancel_sysctr_alarm() RPC call */
 
+/* Siemens specific API extension */
+#define TIMER_FUNC_CTRL_SIEMENS_PMIC_WDOG 20U  /*!< Index for sc_timer_ctrl_pmic_wdog() RPC call */
+
 #endif /* SC_RPC_H */

include/firmware/imx/sci/sci.h

@@ -123,6 +123,7 @@ int sc_rm_set_master_sid(sc_ipc_t ipc, sc_rsrc_t resource, sc_rm_sid_t sid);
 
 /* Timer API */
 int sc_timer_set_wdog_window(sc_ipc_t ipc, sc_timer_wdog_time_t window);
+int sc_timer_control_siemens_pmic_wdog(sc_ipc_t ipc, u8 cmd);
 
 /* SECO API */
 int sc_seco_authenticate(sc_ipc_t ipc, sc_seco_auth_cmd_t cmd,