watchdog: NXP LPC18xx Watchdog Timer Driver

This commit adds support for the watchdog timer found in NXP LPC SoCs
family, which includes LPC18xx/LPC43xx. Other SoCs in that family may
share the same watchdog hardware.

Watchdog driver registers a restart handler that will restart the system
by performing an incorrect feed after ensuring the watchdog is enabled in
reset mode.

As watchdog cannot be disabled in hardware, driver's stop routine will
regularly send a keepalive ping using a timer.

Signed-off-by: Ariel D'Alessandro <ariel@vanguardiasur.com.ar>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

3 files changed, 352 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 241fafde42cb..b69bd67eea96 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -558,6 +558,17 @@ config DIGICOLOR_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called digicolor_wdt.
 
+config LPC18XX_WATCHDOG
+	tristate "LPC18xx/43xx Watchdog"
+	depends on ARCH_LPC18XX || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here if to include support for the watchdog timer
+	  in NXP LPC SoCs family, which includes LPC18xx/LPC43xx
+	  processors.
+	  To compile this driver as a module, choose M here: the
+	  module will be called lpc18xx_wdt.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 59ea9a1b8e76..1b0ef48bf19a 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -66,6 +66,7 @@ obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
 obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
 obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
+obj-$(CONFIG_LPC18XX_WATCHDOG) += lpc18xx_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
diff --git a/drivers/watchdog/lpc18xx_wdt.c b/drivers/watchdog/lpc18xx_wdt.c
new file mode 100644
index 000000000000..00ff5bdd2db0
--- /dev/null
+++ b/drivers/watchdog/lpc18xx_wdt.c
@@ -0,0 +1,340 @@
+/*
+ * NXP LPC18xx Watchdog Timer (WDT)
+ *
+ * Copyright (c) 2015 Ariel D'Alessandro <ariel@vanguardiasur.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * Notes
+ * -----
+ * The Watchdog consists of a fixed divide-by-4 clock pre-scaler and a 24-bit
+ * counter which decrements on every clock cycle.
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+
+/* Registers */
+#define LPC18XX_WDT_MOD			0x00
+#define LPC18XX_WDT_MOD_WDEN		BIT(0)
+#define LPC18XX_WDT_MOD_WDRESET		BIT(1)
+
+#define LPC18XX_WDT_TC			0x04
+#define LPC18XX_WDT_TC_MIN		0xff
+#define LPC18XX_WDT_TC_MAX		0xffffff
+
+#define LPC18XX_WDT_FEED		0x08
+#define LPC18XX_WDT_FEED_MAGIC1		0xaa
+#define LPC18XX_WDT_FEED_MAGIC2		0x55
+
+#define LPC18XX_WDT_TV			0x0c
+
+/* Clock pre-scaler */
+#define LPC18XX_WDT_CLK_DIV		4
+
+/* Timeout values in seconds */
+#define LPC18XX_WDT_DEF_TIMEOUT		30U
+
+static int heartbeat;
+module_param(heartbeat, int, 0);
+MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds (default="
+		 __MODULE_STRING(LPC18XX_WDT_DEF_TIMEOUT) ")");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+struct lpc18xx_wdt_dev {
+	struct watchdog_device	wdt_dev;
+	struct clk		*reg_clk;
+	struct clk		*wdt_clk;
+	unsigned long		clk_rate;
+	void __iomem		*base;
+	struct timer_list	timer;
+	struct notifier_block	restart_handler;
+	spinlock_t		lock;
+};
+
+static int lpc18xx_wdt_feed(struct watchdog_device *wdt_dev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
+	unsigned long flags;
+
+	/*
+	 * An abort condition will occur if an interrupt happens during the feed
+	 * sequence.
+	 */
+	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
+	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
+
+	return 0;
+}
+
+static void lpc18xx_wdt_timer_feed(unsigned long data)
+{
+	struct watchdog_device *wdt_dev = (struct watchdog_device *)data;
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
+
+	lpc18xx_wdt_feed(wdt_dev);
+
+	/* Use safe value (1/2 of real timeout) */
+	mod_timer(&lpc18xx_wdt->timer, jiffies +
+		  msecs_to_jiffies((wdt_dev->timeout * MSEC_PER_SEC) / 2));
+}
+
+/*
+ * Since LPC18xx Watchdog cannot be disabled in hardware, we must keep feeding
+ * it with a timer until userspace watchdog software takes over.
+ */
+static int lpc18xx_wdt_stop(struct watchdog_device *wdt_dev)
+{
+	lpc18xx_wdt_timer_feed((unsigned long)wdt_dev);
+
+	return 0;
+}
+
+static void __lpc18xx_wdt_set_timeout(struct lpc18xx_wdt_dev *lpc18xx_wdt)
+{
+	unsigned int val;
+
+	val = DIV_ROUND_UP(lpc18xx_wdt->wdt_dev.timeout * lpc18xx_wdt->clk_rate,
+			   LPC18XX_WDT_CLK_DIV);
+	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_TC);
+}
+
+static int lpc18xx_wdt_set_timeout(struct watchdog_device *wdt_dev,
+				   unsigned int new_timeout)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
+
+	lpc18xx_wdt->wdt_dev.timeout = new_timeout;
+	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
+
+	return 0;
+}
+
+unsigned int lpc18xx_wdt_get_timeleft(struct watchdog_device *wdt_dev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
+	unsigned int val;
+
+	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_TV);
+	return (val * LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
+}
+
+static int lpc18xx_wdt_start(struct watchdog_device *wdt_dev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = watchdog_get_drvdata(wdt_dev);
+	unsigned int val;
+
+	if (timer_pending(&lpc18xx_wdt->timer))
+		del_timer(&lpc18xx_wdt->timer);
+
+	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
+	val |= LPC18XX_WDT_MOD_WDEN;
+	val |= LPC18XX_WDT_MOD_WDRESET;
+	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
+
+	/*
+	 * Setting the WDEN bit in the WDMOD register is not sufficient to
+	 * enable the Watchdog. A valid feed sequence must be completed after
+	 * setting WDEN before the Watchdog is capable of generating a reset.
+	 */
+	lpc18xx_wdt_feed(wdt_dev);
+
+	return 0;
+}
+
+static struct watchdog_info lpc18xx_wdt_info = {
+	.identity	= "NXP LPC18xx Watchdog",
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops lpc18xx_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= lpc18xx_wdt_start,
+	.stop		= lpc18xx_wdt_stop,
+	.ping		= lpc18xx_wdt_feed,
+	.set_timeout	= lpc18xx_wdt_set_timeout,
+	.get_timeleft	= lpc18xx_wdt_get_timeleft,
+};
+
+static int lpc18xx_wdt_restart(struct notifier_block *this, unsigned long mode,
+			       void *cmd)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = container_of(this,
+				struct lpc18xx_wdt_dev, restart_handler);
+	unsigned long flags;
+	int val;
+
+	/*
+	 * Incorrect feed sequence causes immediate watchdog reset if enabled.
+	 */
+	spin_lock_irqsave(&lpc18xx_wdt->lock, flags);
+
+	val = readl(lpc18xx_wdt->base + LPC18XX_WDT_MOD);
+	val |= LPC18XX_WDT_MOD_WDEN;
+	val |= LPC18XX_WDT_MOD_WDRESET;
+	writel(val, lpc18xx_wdt->base + LPC18XX_WDT_MOD);
+
+	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+	writel(LPC18XX_WDT_FEED_MAGIC2, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+
+	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+	writel(LPC18XX_WDT_FEED_MAGIC1, lpc18xx_wdt->base + LPC18XX_WDT_FEED);
+
+	spin_unlock_irqrestore(&lpc18xx_wdt->lock, flags);
+
+	return NOTIFY_OK;
+}
+
+static int lpc18xx_wdt_probe(struct platform_device *pdev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt;
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	int ret;
+
+	lpc18xx_wdt = devm_kzalloc(dev, sizeof(*lpc18xx_wdt), GFP_KERNEL);
+	if (!lpc18xx_wdt)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	lpc18xx_wdt->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(lpc18xx_wdt->base))
+		return PTR_ERR(lpc18xx_wdt->base);
+
+	lpc18xx_wdt->reg_clk = devm_clk_get(dev, "reg");
+	if (IS_ERR(lpc18xx_wdt->reg_clk)) {
+		dev_err(dev, "failed to get the reg clock\n");
+		return PTR_ERR(lpc18xx_wdt->reg_clk);
+	}
+
+	lpc18xx_wdt->wdt_clk = devm_clk_get(dev, "wdtclk");
+	if (IS_ERR(lpc18xx_wdt->wdt_clk)) {
+		dev_err(dev, "failed to get the wdt clock\n");
+		return PTR_ERR(lpc18xx_wdt->wdt_clk);
+	}
+
+	ret = clk_prepare_enable(lpc18xx_wdt->reg_clk);
+	if (ret) {
+		dev_err(dev, "could not prepare or enable sys clock\n");
+		return ret;
+	}
+
+	ret = clk_prepare_enable(lpc18xx_wdt->wdt_clk);
+	if (ret) {
+		dev_err(dev, "could not prepare or enable wdt clock\n");
+		goto disable_reg_clk;
+	}
+
+	/* We use the clock rate to calculate timeouts */
+	lpc18xx_wdt->clk_rate = clk_get_rate(lpc18xx_wdt->wdt_clk);
+	if (lpc18xx_wdt->clk_rate == 0) {
+		dev_err(dev, "failed to get clock rate\n");
+		ret = -EINVAL;
+		goto disable_wdt_clk;
+	}
+
+	lpc18xx_wdt->wdt_dev.info = &lpc18xx_wdt_info;
+	lpc18xx_wdt->wdt_dev.ops = &lpc18xx_wdt_ops;
+
+	lpc18xx_wdt->wdt_dev.min_timeout = DIV_ROUND_UP(LPC18XX_WDT_TC_MIN *
+				LPC18XX_WDT_CLK_DIV, lpc18xx_wdt->clk_rate);
+
+	lpc18xx_wdt->wdt_dev.max_timeout = (LPC18XX_WDT_TC_MAX *
+				LPC18XX_WDT_CLK_DIV) / lpc18xx_wdt->clk_rate;
+
+	lpc18xx_wdt->wdt_dev.timeout = min(lpc18xx_wdt->wdt_dev.max_timeout,
+					   LPC18XX_WDT_DEF_TIMEOUT);
+
+	spin_lock_init(&lpc18xx_wdt->lock);
+
+	lpc18xx_wdt->wdt_dev.parent = dev;
+	watchdog_set_drvdata(&lpc18xx_wdt->wdt_dev, lpc18xx_wdt);
+
+	ret = watchdog_init_timeout(&lpc18xx_wdt->wdt_dev, heartbeat, dev);
+
+	__lpc18xx_wdt_set_timeout(lpc18xx_wdt);
+
+	setup_timer(&lpc18xx_wdt->timer, lpc18xx_wdt_timer_feed,
+		    (unsigned long)&lpc18xx_wdt->wdt_dev);
+
+	watchdog_set_nowayout(&lpc18xx_wdt->wdt_dev, nowayout);
+
+	platform_set_drvdata(pdev, lpc18xx_wdt);
+
+	ret = watchdog_register_device(&lpc18xx_wdt->wdt_dev);
+	if (ret)
+		goto disable_wdt_clk;
+
+	lpc18xx_wdt->restart_handler.notifier_call = lpc18xx_wdt_restart;
+	lpc18xx_wdt->restart_handler.priority = 128;
+	ret = register_restart_handler(&lpc18xx_wdt->restart_handler);
+	if (ret)
+		dev_warn(dev, "failed to register restart handler: %d\n", ret);
+
+	return 0;
+
+disable_wdt_clk:
+	clk_disable_unprepare(lpc18xx_wdt->wdt_clk);
+disable_reg_clk:
+	clk_disable_unprepare(lpc18xx_wdt->reg_clk);
+	return ret;
+}
+
+static void lpc18xx_wdt_shutdown(struct platform_device *pdev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);
+
+	lpc18xx_wdt_stop(&lpc18xx_wdt->wdt_dev);
+}
+
+static int lpc18xx_wdt_remove(struct platform_device *pdev)
+{
+	struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);
+
+	unregister_restart_handler(&lpc18xx_wdt->restart_handler);
+
+	dev_warn(&pdev->dev, "I quit now, hardware will probably reboot!\n");
+	del_timer(&lpc18xx_wdt->timer);
+
+	watchdog_unregister_device(&lpc18xx_wdt->wdt_dev);
+	clk_disable_unprepare(lpc18xx_wdt->wdt_clk);
+	clk_disable_unprepare(lpc18xx_wdt->reg_clk);
+
+	return 0;
+}
+
+static const struct of_device_id lpc18xx_wdt_match[] = {
+	{ .compatible = "nxp,lpc1850-wwdt" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, lpc18xx_wdt_match);
+
+static struct platform_driver lpc18xx_wdt_driver = {
+	.driver = {
+		.name = "lpc18xx-wdt",
+		.of_match_table	= lpc18xx_wdt_match,
+	},
+	.probe = lpc18xx_wdt_probe,
+	.remove = lpc18xx_wdt_remove,
+	.shutdown = lpc18xx_wdt_shutdown,
+};
+module_platform_driver(lpc18xx_wdt_driver);
+
+MODULE_AUTHOR("Ariel D'Alessandro <ariel@vanguardiasur.com.ar>");
+MODULE_DESCRIPTION("NXP LPC18xx Watchdog Timer Driver");
+MODULE_LICENSE("GPL v2");