watchdog: Add MOXA ART watchdog driver

This patch adds a watchdog driver for the main hardware watchdog timer
found on MOXA ART SoCs.

The MOXA ART SoC provides one writable timer register, restarting
the hardware once it reaches zero. The register is auto decremented
every APB clock cycle.

Signed-off-by: Jonas Jensen <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/moxa,moxart-watchdog.txt

···
+MOXA ART Watchdog timer
+
+Required properties:
+
+- compatible : Must be "moxa,moxart-watchdog"
+- reg : Should contain registers location and length
+- clocks : Should contain phandle for the clock that drives the counter
+
+Example:
+
+	watchdog: watchdog@98500000 {
+		compatible = "moxa,moxart-watchdog";
+		reg = <0x98500000 0x10>;
+		clocks = <&coreclk>;
+	};

drivers/watchdog/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called retu_wdt.
 
+config MOXART_WDT
+	tristate "MOXART watchdog"
+	depends on ARCH_MOXART
+	help
+	  Say Y here to include Watchdog timer support for the watchdog
+	  existing on the MOXA ART SoC series platforms.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called moxart_wdt.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT

drivers/watchdog/Makefile

···
 obj-$(CONFIG_UX500_WATCHDOG) += ux500_wdt.o
 obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
 obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
+obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o

drivers/watchdog/moxart_wdt.c

···
+/*
+ * MOXA ART SoCs watchdog driver.
+ *
+ * Copyright (C) 2013 Jonas Jensen
+ *
+ * Jonas Jensen <[e-mail]>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+#include <linux/moduleparam.h>
+
+#define REG_COUNT			0x4
+#define REG_MODE			0x8
+#define REG_ENABLE			0xC
+
+struct moxart_wdt_dev {
+	struct watchdog_device dev;
+	void __iomem *base;
+	unsigned int clock_frequency;
+};
+
+static int heartbeat;
+
+static int moxart_wdt_stop(struct watchdog_device *wdt_dev)
+{
+	struct moxart_wdt_dev *moxart_wdt = watchdog_get_drvdata(wdt_dev);
+
+	writel(0, moxart_wdt->base + REG_ENABLE);
+
+	return 0;
+}
+
+static int moxart_wdt_start(struct watchdog_device *wdt_dev)
+{
+	struct moxart_wdt_dev *moxart_wdt = watchdog_get_drvdata(wdt_dev);
+
+	writel(moxart_wdt->clock_frequency * wdt_dev->timeout,
+	       moxart_wdt->base + REG_COUNT);
+	writel(0x5ab9, moxart_wdt->base + REG_MODE);
+	writel(0x03, moxart_wdt->base + REG_ENABLE);
+
+	return 0;
+}
+
+static int moxart_wdt_set_timeout(struct watchdog_device *wdt_dev,
+				  unsigned int timeout)
+{
+	wdt_dev->timeout = timeout;
+
+	return 0;
+}
+
+static const struct watchdog_info moxart_wdt_info = {
+	.identity       = "moxart-wdt",
+	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops moxart_wdt_ops = {
+	.owner          = THIS_MODULE,
+	.start          = moxart_wdt_start,
+	.stop           = moxart_wdt_stop,
+	.set_timeout    = moxart_wdt_set_timeout,
+};
+
+static int moxart_wdt_probe(struct platform_device *pdev)
+{
+	struct moxart_wdt_dev *moxart_wdt;
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct resource *res;
+	struct clk *clk;
+	int err;
+	unsigned int max_timeout;
+	bool nowayout = WATCHDOG_NOWAYOUT;
+
+	moxart_wdt = devm_kzalloc(dev, sizeof(*moxart_wdt), GFP_KERNEL);
+	if (!moxart_wdt)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, moxart_wdt);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	moxart_wdt->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(moxart_wdt->base))
+		return PTR_ERR(moxart_wdt->base);
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk)) {
+		pr_err("%s: of_clk_get failed\n", __func__);
+		return PTR_ERR(clk);
+	}
+
+	moxart_wdt->clock_frequency = clk_get_rate(clk);
+	if (moxart_wdt->clock_frequency == 0) {
+		pr_err("%s: incorrect clock frequency\n", __func__);
+		return -EINVAL;
+	}
+
+	max_timeout = UINT_MAX / moxart_wdt->clock_frequency;
+
+	moxart_wdt->dev.info = &moxart_wdt_info;
+	moxart_wdt->dev.ops = &moxart_wdt_ops;
+	moxart_wdt->dev.timeout = max_timeout;
+	moxart_wdt->dev.min_timeout = 1;
+	moxart_wdt->dev.max_timeout = max_timeout;
+	moxart_wdt->dev.parent = dev;
+
+	watchdog_init_timeout(&moxart_wdt->dev, heartbeat, dev);
+	watchdog_set_nowayout(&moxart_wdt->dev, nowayout);
+
+	watchdog_set_drvdata(&moxart_wdt->dev, moxart_wdt);
+
+	err = watchdog_register_device(&moxart_wdt->dev);
+	if (err)
+		return err;
+
+	dev_dbg(dev, "Watchdog enabled (heartbeat=%d sec, nowayout=%d)\n",
+		moxart_wdt->dev.timeout, nowayout);
+
+	return 0;
+}
+
+static int moxart_wdt_remove(struct platform_device *pdev)
+{
+	struct moxart_wdt_dev *moxart_wdt = platform_get_drvdata(pdev);
+
+	moxart_wdt_stop(&moxart_wdt->dev);
+	watchdog_unregister_device(&moxart_wdt->dev);
+
+	return 0;
+}
+
+static const struct of_device_id moxart_watchdog_match[] = {
+	{ .compatible = "moxa,moxart-watchdog" },
+	{ },
+};
+
+static struct platform_driver moxart_wdt_driver = {
+	.probe      = moxart_wdt_probe,
+	.remove     = moxart_wdt_remove,
+	.driver     = {
+		.name		= "moxart-watchdog",
+		.owner		= THIS_MODULE,
+		.of_match_table	= moxart_watchdog_match,
+	},
+};
+module_platform_driver(moxart_wdt_driver);
+
+module_param(heartbeat, int, 0);
+MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds");
+
+MODULE_DESCRIPTION("MOXART watchdog driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jonas Jensen <[e-mail]>");