watchdog: Add Mstar MSC313e WDT driver

It adds a driver for the IP block handling the watchdog timer found for
Mstar MSC313e SoCs and newer.

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Co-developed-by: Romain Perier <romain.perier@gmail.com>
Signed-off-by: Romain Perier <romain.perier@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20210611200801.52139-3-romain.perier@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

MAINTAINERS

@@ -2175,6 +2175,7 @@ F:	arch/arm/boot/dts/mstar-*
 F:	arch/arm/mach-mstar/
 F:	drivers/clk/mstar/
 F:	drivers/gpio/gpio-msc313.c
+F:	drivers/watchdog/msc313e_wdt.c
 F:	include/dt-bindings/clock/mstar-*
 F:	include/dt-bindings/gpio/msc313-gpio.h
 

drivers/watchdog/Kconfig

@@ -989,6 +989,18 @@ config VISCONTI_WATCHDOG
 	  Say Y here to include support for the watchdog timer in Toshiba
 	  Visconti SoCs.
 
+config MSC313E_WATCHDOG
+	tristate "MStar MSC313e watchdog"
+	depends on ARCH_MSTARV7 || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for the Watchdog timer embedded
+	  into MStar MSC313e chips. This will reboot your system when the
+	  timeout is reached.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called msc313e_wdt.
+
 # X86 (i386 + ia64 + x86_64) Architecture
 
 config ACQUIRE_WDT

drivers/watchdog/Makefile

@@ -93,6 +93,7 @@ obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
 obj-$(CONFIG_PM8916_WATCHDOG) += pm8916_wdt.o
 obj-$(CONFIG_ARM_SMC_WATCHDOG) += arm_smc_wdt.o
 obj-$(CONFIG_VISCONTI_WATCHDOG) += visconti_wdt.o
+obj-$(CONFIG_MSC313E_WATCHDOG) += msc313e_wdt.o
 
 # X86 (i386 + ia64 + x86_64) Architecture
 obj-$(CONFIG_ACQUIRE_WDT) += acquirewdt.o

drivers/watchdog/msc313e_wdt.c

@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MStar WDT driver
+ *
+ * Copyright (C) 2019 - 2021 Daniel Palmer
+ * Copyright (C) 2021 Romain Perier
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define REG_WDT_CLR			0x0
+#define REG_WDT_MAX_PRD_L		0x10
+#define REG_WDT_MAX_PRD_H		0x14
+
+#define MSC313E_WDT_MIN_TIMEOUT		1
+#define MSC313E_WDT_DEFAULT_TIMEOUT	30
+
+static unsigned int timeout;
+
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+struct msc313e_wdt_priv {
+	void __iomem *base;
+	struct watchdog_device wdev;
+	struct clk *clk;
+};
+
+static int msc313e_wdt_start(struct watchdog_device *wdev)
+{
+	struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);
+	u32 timeout;
+	int err;
+
+	err = clk_prepare_enable(priv->clk);
+	if (err)
+		return err;
+
+	timeout = wdev->timeout * clk_get_rate(priv->clk);
+	writew(timeout & 0xffff, priv->base + REG_WDT_MAX_PRD_L);
+	writew((timeout >> 16) & 0xffff, priv->base + REG_WDT_MAX_PRD_H);
+	writew(1, priv->base + REG_WDT_CLR);
+	return 0;
+}
+
+static int msc313e_wdt_ping(struct watchdog_device *wdev)
+{
+	struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);
+
+	writew(1, priv->base + REG_WDT_CLR);
+	return 0;
+}
+
+static int msc313e_wdt_stop(struct watchdog_device *wdev)
+{
+	struct msc313e_wdt_priv *priv = watchdog_get_drvdata(wdev);
+
+	writew(0, priv->base + REG_WDT_MAX_PRD_L);
+	writew(0, priv->base + REG_WDT_MAX_PRD_H);
+	writew(0, priv->base + REG_WDT_CLR);
+	clk_disable_unprepare(priv->clk);
+	return 0;
+}
+
+static int msc313e_wdt_settimeout(struct watchdog_device *wdev, unsigned int new_time)
+{
+	wdev->timeout = new_time;
+
+	return msc313e_wdt_start(wdev);
+}
+
+static const struct watchdog_info msc313e_wdt_ident = {
+	.identity = "MSC313e watchdog",
+	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
+};
+
+static const struct watchdog_ops msc313e_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = msc313e_wdt_start,
+	.stop = msc313e_wdt_stop,
+	.ping = msc313e_wdt_ping,
+	.set_timeout = msc313e_wdt_settimeout,
+};
+
+static const struct of_device_id msc313e_wdt_of_match[] = {
+	{ .compatible = "mstar,msc313e-wdt", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, msc313e_wdt_of_match);
+
+static int msc313e_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct msc313e_wdt_priv *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		dev_err(dev, "No input clock\n");
+		return PTR_ERR(priv->clk);
+	}
+
+	priv->wdev.info = &msc313e_wdt_ident,
+	priv->wdev.ops = &msc313e_wdt_ops,
+	priv->wdev.parent = dev;
+	priv->wdev.min_timeout = MSC313E_WDT_MIN_TIMEOUT;
+	priv->wdev.max_timeout = U32_MAX / clk_get_rate(priv->clk);
+	priv->wdev.timeout = MSC313E_WDT_DEFAULT_TIMEOUT;
+
+	watchdog_set_drvdata(&priv->wdev, priv);
+
+	watchdog_init_timeout(&priv->wdev, timeout, dev);
+	watchdog_stop_on_reboot(&priv->wdev);
+	watchdog_stop_on_unregister(&priv->wdev);
+
+	return devm_watchdog_register_device(dev, &priv->wdev);
+}
+
+static int __maybe_unused msc313e_wdt_suspend(struct device *dev)
+{
+	struct msc313e_wdt_priv *priv = dev_get_drvdata(dev);
+
+	if (watchdog_active(&priv->wdev))
+		msc313e_wdt_stop(&priv->wdev);
+
+	return 0;
+}
+
+static int __maybe_unused msc313e_wdt_resume(struct device *dev)
+{
+	struct msc313e_wdt_priv *priv = dev_get_drvdata(dev);
+
+	if (watchdog_active(&priv->wdev))
+		msc313e_wdt_start(&priv->wdev);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(msc313e_wdt_pm_ops, msc313e_wdt_suspend, msc313e_wdt_resume);
+
+static struct platform_driver msc313e_wdt_driver = {
+	.driver = {
+		.name = "msc313e-wdt",
+		.of_match_table = msc313e_wdt_of_match,
+		.pm = &msc313e_wdt_pm_ops,
+	},
+	.probe = msc313e_wdt_probe,
+};
+module_platform_driver(msc313e_wdt_driver);
+
+MODULE_AUTHOR("Daniel Palmer <daniel@thingy.jp>");
+MODULE_DESCRIPTION("Watchdog driver for MStar MSC313e");
+MODULE_LICENSE("GPL v2");