watchdog: Add tegra watchdog

Add a driver for the hardware watchdogs in NVIDIA Tegra SoCs (Tegra30 and
later).  This driver will configure one watchdog timer that will reset the
system in the case of a watchdog timeout.

This driver binds to the nvidia,tegra30-timer device node and gets its
register base from there.

Signed-off-by: Andrew Chew <achew@nvidia.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

3 files changed, 314 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 4b54a0faa167..ce9309152fdf 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -430,6 +430,17 @@ config SIRFSOC_WATCHDOG
 	  Support for CSR SiRFprimaII and SiRFatlasVI watchdog. When
 	  the watchdog triggers the system will be reset.
 
+config TEGRA_WATCHDOG
+	tristate "Tegra watchdog"
+	depends on ARCH_TEGRA || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include support for the watchdog timer
+	  embedded in NVIDIA Tegra SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called tegra_wdt.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 985a66cda76f..1b5f3d5efad5 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
 obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
 obj-$(CONFIG_SIRFSOC_WATCHDOG) += sirfsoc_wdt.o
 obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
+obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 
 # AVR32 Architecture
 obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
diff --git a/drivers/watchdog/tegra_wdt.c b/drivers/watchdog/tegra_wdt.c
new file mode 100644
index 000000000000..750e2a26cb12
--- /dev/null
+++ b/drivers/watchdog/tegra_wdt.c
@@ -0,0 +1,302 @@
+/*
+ * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+/* minimum and maximum watchdog trigger timeout, in seconds */
+#define MIN_WDT_TIMEOUT			1
+#define MAX_WDT_TIMEOUT			255
+
+/*
+ * Base of the WDT registers, from the timer base address.  There are
+ * actually 5 watchdogs that can be configured (by pairing with an available
+ * timer), at bases 0x100 + (WDT ID) * 0x20, where WDT ID is 0 through 4.
+ * This driver only configures the first watchdog (WDT ID 0).
+ */
+#define WDT_BASE			0x100
+#define WDT_ID				0
+
+/*
+ * Register base of the timer that's selected for pairing with the watchdog.
+ * This driver arbitrarily uses timer 5, which is currently unused by
+ * other drivers (in particular, the Tegra clocksource driver).  If this
+ * needs to change, take care that the new timer is not used by the
+ * clocksource driver.
+ */
+#define WDT_TIMER_BASE			0x60
+#define WDT_TIMER_ID			5
+
+/* WDT registers */
+#define WDT_CFG				0x0
+#define WDT_CFG_PERIOD_SHIFT		4
+#define WDT_CFG_PERIOD_MASK		0xff
+#define WDT_CFG_INT_EN			(1 << 12)
+#define WDT_CFG_PMC2CAR_RST_EN		(1 << 15)
+#define WDT_STS				0x4
+#define WDT_STS_COUNT_SHIFT		4
+#define WDT_STS_COUNT_MASK		0xff
+#define WDT_STS_EXP_SHIFT		12
+#define WDT_STS_EXP_MASK		0x3
+#define WDT_CMD				0x8
+#define WDT_CMD_START_COUNTER		(1 << 0)
+#define WDT_CMD_DISABLE_COUNTER		(1 << 1)
+#define WDT_UNLOCK			(0xc)
+#define WDT_UNLOCK_PATTERN		(0xc45a << 0)
+
+/* Timer registers */
+#define TIMER_PTV			0x0
+#define TIMER_EN			(1 << 31)
+#define TIMER_PERIODIC			(1 << 30)
+
+struct tegra_wdt {
+	struct watchdog_device	wdd;
+	void __iomem		*wdt_regs;
+	void __iomem		*tmr_regs;
+};
+
+#define WDT_HEARTBEAT 120
+static int heartbeat = WDT_HEARTBEAT;
+module_param(heartbeat, int, 0);
+MODULE_PARM_DESC(heartbeat,
+	"Watchdog heartbeats in seconds. (default = "
+	__MODULE_STRING(WDT_HEARTBEAT) ")");
+
+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) ")");
+
+static int tegra_wdt_start(struct watchdog_device *wdd)
+{
+	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 val;
+
+	/*
+	 * This thing has a fixed 1MHz clock.  Normally, we would set the
+	 * period to 1 second by writing 1000000ul, but the watchdog system
+	 * reset actually occurs on the 4th expiration of this counter,
+	 * so we set the period to 1/4 of this amount.
+	 */
+	val = 1000000ul / 4;
+	val |= (TIMER_EN | TIMER_PERIODIC);
+	writel(val, wdt->tmr_regs + TIMER_PTV);
+
+	/*
+	 * Set number of periods and start counter.
+	 *
+	 * Interrupt handler is not required for user space
+	 * WDT accesses, since the caller is responsible to ping the
+	 * WDT to reset the counter before expiration, through ioctls.
+	 */
+	val = WDT_TIMER_ID |
+	      (wdd->timeout << WDT_CFG_PERIOD_SHIFT) |
+	      WDT_CFG_PMC2CAR_RST_EN;
+	writel(val, wdt->wdt_regs + WDT_CFG);
+
+	writel(WDT_CMD_START_COUNTER, wdt->wdt_regs + WDT_CMD);
+
+	return 0;
+}
+
+static int tegra_wdt_stop(struct watchdog_device *wdd)
+{
+	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	writel(WDT_UNLOCK_PATTERN, wdt->wdt_regs + WDT_UNLOCK);
+	writel(WDT_CMD_DISABLE_COUNTER, wdt->wdt_regs + WDT_CMD);
+	writel(0, wdt->tmr_regs + TIMER_PTV);
+
+	return 0;
+}
+
+static int tegra_wdt_ping(struct watchdog_device *wdd)
+{
+	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	writel(WDT_CMD_START_COUNTER, wdt->wdt_regs + WDT_CMD);
+
+	return 0;
+}
+
+static int tegra_wdt_set_timeout(struct watchdog_device *wdd,
+				 unsigned int timeout)
+{
+	wdd->timeout = timeout;
+
+	if (watchdog_active(wdd))
+		return tegra_wdt_start(wdd);
+
+	return 0;
+}
+
+static unsigned int tegra_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	struct tegra_wdt *wdt = watchdog_get_drvdata(wdd);
+	u32 val;
+	int count;
+	int exp;
+
+	val = readl(wdt->wdt_regs + WDT_STS);
+
+	/* Current countdown (from timeout) */
+	count = (val >> WDT_STS_COUNT_SHIFT) & WDT_STS_COUNT_MASK;
+
+	/* Number of expirations (we are waiting for the 4th expiration) */
+	exp = (val >> WDT_STS_EXP_SHIFT) & WDT_STS_EXP_MASK;
+
+	/*
+	 * The entire thing is divided by 4 because we are ticking down 4 times
+	 * faster due to needing to wait for the 4th expiration.
+	 */
+	return (((3 - exp) * wdd->timeout) + count) / 4;
+}
+
+static const struct watchdog_info tegra_wdt_info = {
+	.options	= WDIOF_SETTIMEOUT |
+			  WDIOF_MAGICCLOSE |
+			  WDIOF_KEEPALIVEPING,
+	.firmware_version = 0,
+	.identity	= "Tegra Watchdog",
+};
+
+static struct watchdog_ops tegra_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = tegra_wdt_start,
+	.stop = tegra_wdt_stop,
+	.ping = tegra_wdt_ping,
+	.set_timeout = tegra_wdt_set_timeout,
+	.get_timeleft = tegra_wdt_get_timeleft,
+};
+
+static int tegra_wdt_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	struct tegra_wdt *wdt;
+	struct resource *res;
+	void __iomem *regs;
+	int ret;
+
+	/* This is the timer base. */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	/*
+	 * Allocate our watchdog driver data, which has the
+	 * struct watchdog_device nested within it.
+	 */
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	/* Initialize struct tegra_wdt. */
+	wdt->wdt_regs = regs + WDT_BASE;
+	wdt->tmr_regs = regs + WDT_TIMER_BASE;
+
+	/* Initialize struct watchdog_device. */
+	wdd = &wdt->wdd;
+	wdd->timeout = heartbeat;
+	wdd->info = &tegra_wdt_info;
+	wdd->ops = &tegra_wdt_ops;
+	wdd->min_timeout = MIN_WDT_TIMEOUT;
+	wdd->max_timeout = MAX_WDT_TIMEOUT;
+
+	watchdog_set_drvdata(wdd, wdt);
+
+	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 (heartbeat = %d sec, nowayout = %d)\n",
+		 heartbeat, nowayout);
+
+	return 0;
+}
+
+static int tegra_wdt_remove(struct platform_device *pdev)
+{
+	struct tegra_wdt *wdt = platform_get_drvdata(pdev);
+
+	tegra_wdt_stop(&wdt->wdd);
+
+	watchdog_unregister_device(&wdt->wdd);
+
+	dev_info(&pdev->dev, "removed wdt\n");
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int tegra_wdt_runtime_suspend(struct device *dev)
+{
+	struct tegra_wdt *wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(&wdt->wdd))
+		tegra_wdt_stop(&wdt->wdd);
+
+	return 0;
+}
+
+static int tegra_wdt_runtime_resume(struct device *dev)
+{
+	struct tegra_wdt *wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(&wdt->wdd))
+		tegra_wdt_start(&wdt->wdd);
+
+	return 0;
+}
+#endif
+
+static const struct of_device_id tegra_wdt_of_match[] = {
+	{ .compatible = "nvidia,tegra30-timer", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tegra_wdt_of_match);
+
+static const struct dev_pm_ops tegra_wdt_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(tegra_wdt_runtime_suspend,
+				tegra_wdt_runtime_resume)
+};
+
+static struct platform_driver tegra_wdt_driver = {
+	.probe		= tegra_wdt_probe,
+	.remove		= tegra_wdt_remove,
+	.driver		= {
+		.owner	= THIS_MODULE,
+		.name	= "tegra-wdt",
+		.pm	= &tegra_wdt_pm_ops,
+		.of_match_table = tegra_wdt_of_match,
+	},
+};
+module_platform_driver(tegra_wdt_driver);
+
+MODULE_AUTHOR("NVIDIA Corporation");
+MODULE_DESCRIPTION("Tegra Watchdog Driver");
+MODULE_LICENSE("GPL v2");