[PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver

[Evan Benn]

From: Julius Werner <jwerner@xxxxxxxxxxxx>

This patch adds a stub watchdog driver that can be used on ARM systems
with a Secure Monitor firmware to forward watchdog operations to
firmware via a Secure Monitor Call. This may be useful for platforms
using TrustZone that want the Secure Monitor firmware to have the final
control over the watchdog.

Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx>
Signed-off-by: Evan Benn <evanbenn@xxxxxxxxxxxx>
---

 MAINTAINERS                    |   1 +
 arch/arm64/configs/defconfig   |   1 +
 drivers/watchdog/Kconfig       |  12 +++
 drivers/watchdog/Makefile      |   1 +
 drivers/watchdog/arm_smc_wdt.c | 191 +++++++++++++++++++++++++++++++++
 5 files changed, 206 insertions(+)
 create mode 100644 drivers/watchdog/arm_smc_wdt.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5c45536e1177..71df3c110fdb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1426,6 +1426,7 @@ M:	Julius Werner <jwerner@xxxxxxxxxxxx>
 R:	Evan Benn <evanbenn@xxxxxxxxxxxx>
 S:	Maintained
 F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
+F:	drivers/watchdog/arm_smc_wdt.c
 
 ARM SMMU DRIVERS
 M:	Will Deacon <will@xxxxxxxxxx>
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index b2f667307f82..8527db9e92a6 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -451,6 +451,7 @@ CONFIG_QCOM_TSENS=y
 CONFIG_UNIPHIER_THERMAL=y
 CONFIG_WATCHDOG=y
 CONFIG_ARM_SP805_WATCHDOG=y
+CONFIG_ARM_SMC_WATCHDOG=y
 CONFIG_S3C2410_WATCHDOG=y
 CONFIG_DW_WATCHDOG=y
 CONFIG_SUNXI_WATCHDOG=m
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index cec868f8db3f..0f7f93342051 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -857,6 +857,18 @@ config DIGICOLOR_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called digicolor_wdt.
 
+config ARM_SMC_WATCHDOG
+	tristate "ARM Secure Monitor Call based watchdog support"
+	depends on ARM || ARM64
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for a watchdog timer
+	  implemented by the EL3 Secure Monitor on ARM platforms.
+	  Requires firmware support.
+	  To compile this driver as a module, choose M here: the
+	  module will be called arm_smc_wdt.
+
+
 config LPC18XX_WATCHDOG
 	tristate "LPC18xx/43xx Watchdog"
 	depends on ARCH_LPC18XX || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee352bf3372..a1e6d83a7659 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
 obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
 obj-$(CONFIG_RTD119X_WATCHDOG) += rtd119x_wdt.o
 obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
+obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
diff --git a/drivers/watchdog/arm_smc_wdt.c b/drivers/watchdog/arm_smc_wdt.c
new file mode 100644
index 000000000000..58e7294136ef
--- /dev/null
+++ b/drivers/watchdog/arm_smc_wdt.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARM Secure Monitor Call watchdog driver
+ *
+ * Copyright 2018 The Chromium OS Authors. All rights reserved.
+ *
+ * Julius Werner <jwerner@xxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Based on mtk_wdt.c
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+#include <uapi/linux/psci.h>
+
+#define DRV_NAME		"arm_smc_wdt"
+#define DRV_VERSION		"1.0"
+
+#define SMCWD_FUNC_ID		0x82003d06
+
+enum smcwd_call {
+	SMCWD_INFO		= 0,
+	SMCWD_SET_TIMEOUT	= 1,
+	SMCWD_ENABLE		= 2,
+	SMCWD_PET		= 3,
+};
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+static unsigned int timeout;
+
+static int smcwd_call(enum smcwd_call call, unsigned long arg,
+		      struct arm_smccc_res *res)
+{
+	struct arm_smccc_res local_res;
+
+	if (!res)
+		res = &local_res;
+
+	arm_smccc_smc(SMCWD_FUNC_ID, call, arg, 0, 0, 0, 0, 0, res);
+
+	if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
+		return -ENOTSUPP;
+	if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
+		return -EINVAL;
+	if ((int)res->a0 < 0)
+		return -EIO;
+	return res->a0;
+}
+
+static int smcwd_ping(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_PET, 0, NULL);
+}
+
+static int smcwd_set_timeout(struct watchdog_device *wdd,
+				unsigned int timeout)
+{
+	int res;
+
+	res = smcwd_call(SMCWD_SET_TIMEOUT, timeout, NULL);
+	if (!res)
+		wdd->timeout = timeout;
+	return res;
+}
+
+static int smcwd_stop(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_ENABLE, 0, NULL);
+}
+
+static int smcwd_start(struct watchdog_device *wdd)
+{
+	return smcwd_call(SMCWD_ENABLE, 1, NULL);
+}
+
+static const struct watchdog_info smcwd_info = {
+	.identity	= DRV_NAME,
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops smcwd_ops = {
+	.owner		= THIS_MODULE,
+	.start		= smcwd_start,
+	.stop		= smcwd_stop,
+	.ping		= smcwd_ping,
+	.set_timeout	= smcwd_set_timeout,
+};
+
+static int smcwd_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	int err;
+	struct arm_smccc_res res;
+
+	err = smcwd_call(SMCWD_INFO, 0, &res);
+	if (err < 0)
+		return err;
+
+	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
+	if (!wdd)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, wdd);
+
+	wdd->info = &smcwd_info;
+	wdd->ops = &smcwd_ops;
+	wdd->timeout = res.a2;
+	wdd->max_timeout = res.a2;
+	wdd->min_timeout = res.a1;
+	wdd->parent = &pdev->dev;
+
+	watchdog_set_nowayout(wdd, nowayout);
+	watchdog_init_timeout(wdd, timeout, &pdev->dev);
+	err = smcwd_set_timeout(wdd, wdd->timeout);
+	if (err)
+		return err;
+
+	err = watchdog_register_device(wdd);
+	if (err)
+		return err;
+
+	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)\n",
+			wdd->timeout, nowayout);
+
+	return 0;
+}
+
+static void smcwd_shutdown(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+
+	if (watchdog_active(wdd))
+		smcwd_stop(wdd);
+}
+
+static int smcwd_remove(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd = platform_get_drvdata(pdev);
+
+	watchdog_unregister_device(wdd);
+
+	return 0;
+}
+
+static const struct of_device_id smcwd_dt_ids[] = {
+	{ .compatible = "arm,smc-wdt" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
+
+static struct platform_driver smcwd_driver = {
+	.probe		= smcwd_probe,
+	.remove		= smcwd_remove,
+	.shutdown	= smcwd_shutdown,
+	.driver		= {
+		.name		= DRV_NAME,
+		.of_match_table	= smcwd_dt_ids,
+	},
+};
+
+module_platform_driver(smcwd_driver);
+
+module_param(timeout, uint, 0);
+MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
+
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Julius Werner <jwerner@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
+MODULE_VERSION(DRV_VERSION);
-- 
2.25.0.265.gbab2e86ba0-goog