watchdog: add a driver to support SAMA5D4 watchdog timer

From SAMA5D4, the watchdog timer is upgrated with a new feature,
which is describled as in the datasheet, "WDT_MR can be written
until a LOCKMR command is issued in WDT_CR".
That is to say, as long as the bootstrap and u-boot don't issue
a LOCKMR command, WDT_MR can be written more than once in the driver.

So the SAMA5D4 watchdog driver's implementation is different from
the at91sam9260 watchdog driver implemented in file at91sam9_wdt.c.
The user application open the device file to enable the watchdog timer
hardware, and close to disable it, and set the watchdog timer timeout
by seting WDV and WDD fields of WDT_MR register, and ping the watchdog
by issuing WDRSTT command to WDT_CR register with hard-coded key.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/Kconfig

@@ -188,6 +188,15 @@ config AT91SAM9X_WATCHDOG
 	  Watchdog timer embedded into AT91SAM9X and AT91CAP9 chips. This will
 	  reboot your system when the timeout is reached.
 
+config SAMA5D4_WATCHDOG
+	tristate "Atmel SAMA5D4 Watchdog Timer"
+	depends on ARCH_AT91
+	select WATCHDOG_CORE
+	help
+	  Atmel SAMA5D4 watchdog timer is embedded into SAMA5D4 chips.
+	  Its Watchdog Timer Mode Register can be written more than once.
+	  This will reboot your system when the timeout is reached.
+
 config CADENCE_WATCHDOG
 	tristate "Cadence Watchdog Timer"
 	depends on HAS_IOMEM

drivers/watchdog/Makefile

@@ -41,6 +41,7 @@ obj-$(CONFIG_IXP4XX_WATCHDOG) += ixp4xx_wdt.o
 obj-$(CONFIG_KS8695_WATCHDOG) += ks8695_wdt.o
 obj-$(CONFIG_S3C2410_WATCHDOG) += s3c2410_wdt.o
 obj-$(CONFIG_SA1100_WATCHDOG) += sa1100_wdt.o
+obj-$(CONFIG_SAMA5D4_WATCHDOG) += sama5d4_wdt.o
 obj-$(CONFIG_DW_WATCHDOG) += dw_wdt.o
 obj-$(CONFIG_EP93XX_WATCHDOG) += ep93xx_wdt.o
 obj-$(CONFIG_PNX4008_WATCHDOG) += pnx4008_wdt.o

drivers/watchdog/at91sam9_wdt.h

@@ -22,11 +22,13 @@
 
 #define AT91_WDT_MR		0x04			/* Watchdog Mode Register */
 #define		AT91_WDT_WDV		(0xfff << 0)		/* Counter Value */
+#define			AT91_WDT_SET_WDV(x)	((x) & AT91_WDT_WDV)
 #define		AT91_WDT_WDFIEN		(1     << 12)		/* Fault Interrupt Enable */
 #define		AT91_WDT_WDRSTEN	(1     << 13)		/* Reset Processor */
 #define		AT91_WDT_WDRPROC	(1     << 14)		/* Timer Restart */
 #define		AT91_WDT_WDDIS		(1     << 15)		/* Watchdog Disable */
 #define		AT91_WDT_WDD		(0xfff << 16)		/* Delta Value */
+#define			AT91_WDT_SET_WDD(x)	(((x) << 16) & AT91_WDT_WDD)
 #define		AT91_WDT_WDDBGHLT	(1     << 28)		/* Debug Halt */
 #define		AT91_WDT_WDIDLEHLT	(1     << 29)		/* Idle Halt */
 

drivers/watchdog/sama5d4_wdt.c

@@ -0,0 +1,280 @@
+/*
+ * Driver for Atmel SAMA5D4 Watchdog Timer
+ *
+ * Copyright (C) 2015 Atmel Corporation
+ *
+ * Licensed under GPLv2.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+
+#include "at91sam9_wdt.h"
+
+/* minimum and maximum watchdog timeout, in seconds */
+#define MIN_WDT_TIMEOUT		1
+#define MAX_WDT_TIMEOUT		16
+#define WDT_DEFAULT_TIMEOUT	MAX_WDT_TIMEOUT
+
+#define WDT_SEC2TICKS(s)	((s) ? (((s) << 8) - 1) : 0)
+
+struct sama5d4_wdt {
+	struct watchdog_device	wdd;
+	void __iomem		*reg_base;
+	u32	config;
+};
+
+static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
+static bool nowayout = WATCHDOG_NOWAYOUT;
+
+module_param(wdt_timeout, int, 0);
+MODULE_PARM_DESC(wdt_timeout,
+	"Watchdog timeout in seconds. (default = "
+	__MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
+
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout,
+	"Watchdog cannot be stopped once started (default="
+	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+#define wdt_read(wdt, field) \
+	readl_relaxed((wdt)->reg_base + (field))
+
+#define wdt_write(wtd, field, val) \
+	writel_relaxed((val), (wdt)->reg_base + (field))
+
+static int sama5d4_wdt_start(struct watchdog_device *wdd)
+{
+	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 reg;
+
+	reg = wdt_read(wdt, AT91_WDT_MR);
+	reg &= ~AT91_WDT_WDDIS;
+	wdt_write(wdt, AT91_WDT_MR, reg);
+
+	return 0;
+}
+
+static int sama5d4_wdt_stop(struct watchdog_device *wdd)
+{
+	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 reg;
+
+	reg = wdt_read(wdt, AT91_WDT_MR);
+	reg |= AT91_WDT_WDDIS;
+	wdt_write(wdt, AT91_WDT_MR, reg);
+
+	return 0;
+}
+
+static int sama5d4_wdt_ping(struct watchdog_device *wdd)
+{
+	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
+
+	return 0;
+}
+
+static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
+				 unsigned int timeout)
+{
+	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 value = WDT_SEC2TICKS(timeout);
+	u32 reg;
+
+	reg = wdt_read(wdt, AT91_WDT_MR);
+	reg &= ~AT91_WDT_WDV;
+	reg &= ~AT91_WDT_WDD;
+	reg |= AT91_WDT_SET_WDV(value);
+	reg |= AT91_WDT_SET_WDD(value);
+	wdt_write(wdt, AT91_WDT_MR, reg);
+
+	wdd->timeout = timeout;
+
+	return 0;
+}
+
+static const struct watchdog_info sama5d4_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+	.identity = "Atmel SAMA5D4 Watchdog",
+};
+
+static struct watchdog_ops sama5d4_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = sama5d4_wdt_start,
+	.stop = sama5d4_wdt_stop,
+	.ping = sama5d4_wdt_ping,
+	.set_timeout = sama5d4_wdt_set_timeout,
+};
+
+static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
+{
+	struct sama5d4_wdt *wdt = platform_get_drvdata(dev_id);
+
+	if (wdt_read(wdt, AT91_WDT_SR)) {
+		pr_crit("Atmel Watchdog Software Reset\n");
+		emergency_restart();
+		pr_crit("Reboot didn't succeed\n");
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
+{
+	const char *tmp;
+
+	wdt->config = AT91_WDT_WDDIS;
+
+	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
+	    !strcmp(tmp, "software"))
+		wdt->config |= AT91_WDT_WDFIEN;
+	else
+		wdt->config |= AT91_WDT_WDRSTEN;
+
+	if (of_property_read_bool(np, "atmel,idle-halt"))
+		wdt->config |= AT91_WDT_WDIDLEHLT;
+
+	if (of_property_read_bool(np, "atmel,dbg-halt"))
+		wdt->config |= AT91_WDT_WDDBGHLT;
+
+	return 0;
+}
+
+static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
+{
+	struct watchdog_device *wdd = &wdt->wdd;
+	u32 value = WDT_SEC2TICKS(wdd->timeout);
+	u32 reg;
+
+	/*
+	 * Because the fields WDV and WDD must not be modified when the WDDIS
+	 * bit is set, so clear the WDDIS bit before writing the WDT_MR.
+	 */
+	reg = wdt_read(wdt, AT91_WDT_MR);
+	reg &= ~AT91_WDT_WDDIS;
+	wdt_write(wdt, AT91_WDT_MR, reg);
+
+	reg = wdt->config;
+	reg |= AT91_WDT_SET_WDD(value);
+	reg |= AT91_WDT_SET_WDV(value);
+
+	wdt_write(wdt, AT91_WDT_MR, reg);
+
+	return 0;
+}
+
+static int sama5d4_wdt_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	struct sama5d4_wdt *wdt;
+	struct resource *res;
+	void __iomem *regs;
+	u32 irq = 0;
+	int ret;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	wdd = &wdt->wdd;
+	wdd->timeout = wdt_timeout;
+	wdd->info = &sama5d4_wdt_info;
+	wdd->ops = &sama5d4_wdt_ops;
+	wdd->min_timeout = MIN_WDT_TIMEOUT;
+	wdd->max_timeout = MAX_WDT_TIMEOUT;
+
+	watchdog_set_drvdata(wdd, wdt);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	wdt->reg_base = regs;
+
+	if (pdev->dev.of_node) {
+		irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
+		if (!irq)
+			dev_warn(&pdev->dev, "failed to get IRQ from DT\n");
+
+		ret = of_sama5d4_wdt_init(pdev->dev.of_node, wdt);
+		if (ret)
+			return ret;
+	}
+
+	if ((wdt->config & AT91_WDT_WDFIEN) && irq) {
+		ret = devm_request_irq(&pdev->dev, irq, sama5d4_wdt_irq_handler,
+				       IRQF_SHARED | IRQF_IRQPOLL |
+				       IRQF_NO_SUSPEND, pdev->name, pdev);
+		if (ret) {
+			dev_err(&pdev->dev,
+				"cannot register interrupt handler\n");
+			return ret;
+		}
+	}
+
+	ret = watchdog_init_timeout(wdd, wdt_timeout, &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to set timeout value\n");
+		return ret;
+	}
+
+	ret = sama5d4_wdt_init(wdt);
+	if (ret)
+		return ret;
+
+	watchdog_set_nowayout(wdd, nowayout);
+
+	ret = watchdog_register_device(wdd);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register watchdog device\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, wdt);
+
+	dev_info(&pdev->dev, "initialized (timeout = %d sec, nowayout = %d)\n",
+		 wdt_timeout, nowayout);
+
+	return 0;
+}
+
+static int sama5d4_wdt_remove(struct platform_device *pdev)
+{
+	struct sama5d4_wdt *wdt = platform_get_drvdata(pdev);
+
+	sama5d4_wdt_stop(&wdt->wdd);
+
+	watchdog_unregister_device(&wdt->wdd);
+
+	return 0;
+}
+
+static const struct of_device_id sama5d4_wdt_of_match[] = {
+	{ .compatible = "atmel,sama5d4-wdt", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
+
+static struct platform_driver sama5d4_wdt_driver = {
+	.probe		= sama5d4_wdt_probe,
+	.remove		= sama5d4_wdt_remove,
+	.driver		= {
+		.name	= "sama5d4_wdt",
+		.of_match_table = sama5d4_wdt_of_match,
+	}
+};
+module_platform_driver(sama5d4_wdt_driver);
+
+MODULE_AUTHOR("Atmel Corporation");
+MODULE_DESCRIPTION("Atmel SAMA5D4 Watchdog Timer driver");
+MODULE_LICENSE("GPL v2");