watchdog: arm_smc_wdt: add watchdog support

Implement a ARM SMCCC based driver that allow to use
a secure watchdog on the platform.

Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Patrick Delaunay <patrick.delaunay@foss.st.com>

drivers/watchdog/Kconfig

@@ -361,6 +361,14 @@ config WDT_TANGIER
 	  Intel Tangier SoC. If you're using a board with Intel Tangier
 	  SoC, say Y here.
 
+config WDT_ARM_SMC
+	bool "ARM SMC watchdog timer support"
+	depends on WDT && ARM_SMCCC
+	imply WATCHDOG
+	help
+	  Select this to enable Arm SMC watchdog timer. This watchdog will manage
+	  a watchdog based on ARM SMCCC communication.
+
 config SPL_WDT
 	bool "Enable driver model for watchdog timer drivers in SPL"
 	depends on SPL_DM

drivers/watchdog/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_$(SPL_TPL_)WDT) += wdt-uclass.o
 obj-$(CONFIG_WDT_SANDBOX) += sandbox_wdt.o
 obj-$(CONFIG_WDT_ALARM_SANDBOX) += sandbox_alarm-wdt.o
 obj-$(CONFIG_WDT_APPLE) += apple_wdt.o
+obj-$(CONFIG_WDT_ARM_SMC) += arm_smc_wdt.o
 obj-$(CONFIG_WDT_ARMADA_37XX) += armada-37xx-wdt.o
 obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
 obj-$(CONFIG_WDT_AST2600) += ast2600_wdt.o

drivers/watchdog/arm_smc_wdt.c

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * ARM Secure Monitor Call watchdog driver
+ * Copyright (C) 2022, STMicroelectronics - All Rights Reserved
+ * This file is based on Linux driver drivers/watchdog/arm_smc_wdt.c
+ */
+
+#define LOG_CATEGORY UCLASS_WDT
+
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <linux/arm-smccc.h>
+#include <linux/psci.h>
+#include <wdt.h>
+
+#define DRV_NAME		"arm_smc_wdt"
+
+#define WDT_TIMEOUT_SECS(TIMEOUT)	((TIMEOUT) / 1000)
+
+enum smcwd_call {
+	SMCWD_INIT		= 0,
+	SMCWD_SET_TIMEOUT	= 1,
+	SMCWD_ENABLE		= 2,
+	SMCWD_PET		= 3,
+	SMCWD_GET_TIMELEFT	= 4,
+};
+
+struct smcwd_priv_data {
+	u32 smc_id;
+	unsigned int min_timeout;
+	unsigned int max_timeout;
+};
+
+static int smcwd_call(struct udevice *dev, enum smcwd_call call,
+		      unsigned long arg, struct arm_smccc_res *res)
+{
+	struct smcwd_priv_data *priv = dev_get_priv(dev);
+	struct arm_smccc_res local_res;
+
+	if (!res)
+		res = &local_res;
+
+	arm_smccc_smc(priv->smc_id, call, arg, 0, 0, 0, 0, 0, res);
+
+	if (res->a0 == PSCI_RET_NOT_SUPPORTED)
+		return -ENODEV;
+	if (res->a0 == PSCI_RET_INVALID_PARAMS)
+		return -EINVAL;
+	if (res->a0 != PSCI_RET_SUCCESS)
+		return -EIO;
+
+	return 0;
+}
+
+static int smcwd_reset(struct udevice *dev)
+{
+	return smcwd_call(dev, SMCWD_PET, 0, NULL);
+}
+
+static int smcwd_stop(struct udevice *dev)
+{
+	return smcwd_call(dev, SMCWD_ENABLE, 0, NULL);
+}
+
+static int smcwd_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+	struct smcwd_priv_data *priv = dev_get_priv(dev);
+	u64 timeout_sec = WDT_TIMEOUT_SECS(timeout_ms);
+	int err;
+
+	if (timeout_sec < priv->min_timeout || timeout_sec > priv->max_timeout)	{
+		dev_err(dev, "Timeout value not supported\n");
+		return -EINVAL;
+	}
+
+	err = smcwd_call(dev, SMCWD_SET_TIMEOUT, timeout_sec, NULL);
+	if (err) {
+		dev_err(dev, "Timeout out configuration failed\n");
+		return err;
+	}
+
+	return smcwd_call(dev, SMCWD_ENABLE, 1, NULL);
+}
+
+static int smcwd_probe(struct udevice *dev)
+{
+	struct smcwd_priv_data *priv = dev_get_priv(dev);
+	struct arm_smccc_res res;
+	int err;
+
+	priv->smc_id = dev_read_u32_default(dev, "arm,smc-id", 0x82003D06);
+
+	err = smcwd_call(dev, SMCWD_INIT, 0, &res);
+	if (err < 0) {
+		dev_err(dev, "Init failed %i\n", err);
+		return err;
+	}
+
+	priv->min_timeout = res.a1;
+	priv->max_timeout = res.a2;
+
+	return 0;
+}
+
+static const struct wdt_ops smcwd_ops = {
+	.start		= smcwd_start,
+	.stop		= smcwd_stop,
+	.reset		= smcwd_reset,
+};
+
+static const struct udevice_id smcwd_dt_ids[] = {
+	{ .compatible = "arm,smc-wdt" },
+	{}
+};
+
+U_BOOT_DRIVER(wdt_sandbox) = {
+	.name = "smcwd",
+	.id = UCLASS_WDT,
+	.of_match = smcwd_dt_ids,
+	.priv_auto = sizeof(struct smcwd_priv_data),
+	.probe = smcwd_probe,
+	.ops = &smcwd_ops,
+};