watchdog: Add support for Armada 37xx CPU watchdog

This adds support for the CPU watchdog found on Marvell Armada 37xx
SoCs.

There are 4 counters which can be set as CPU watchdog counters.
This driver uses the second counter (ID 1, counting from 0) as watchdog
counter, and first counter (ID 0) to implement pinging on the second
counter without the need to disable it.

Since counters IDs 2 and 3 are enabled already before even U-Boot
starts, this driver does not use them at all, for example by adding a
device tree property for counter selection.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

3 files changed, 399 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 5637d8be31e0..2d64333f4782 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -273,6 +273,17 @@ config ARM_SBSA_WATCHDOG
 	  To compile this driver as module, choose M here: The module
 	  will be called sbsa_gwdt.
 
+config ARMADA_37XX_WATCHDOG
+	tristate "Armada 37xx watchdog"
+	depends on ARCH_MVEBU || COMPILE_TEST
+	select MFD_SYSCON
+	select WATCHDOG_CORE
+	help
+	   Say Y here to include support for the watchdog timer found on
+	   Marvell Armada 37xx SoCs.
+	   To compile this driver as a module, choose M here: the
+	   module will be called armada_37xx_wdt.
+
 config ASM9260_WATCHDOG
 	tristate "Alphascale ASM9260 watchdog"
 	depends on MACH_ASM9260 || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index bf92e7bf9ce0..f69cdff5ad7f 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
 # ARM Architecture
 obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
 obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
+obj-$(CONFIG_ARMADA_37XX_WATCHDOG) += armada_37xx_wdt.o
 obj-$(CONFIG_ASM9260_WATCHDOG) += asm9260_wdt.o
 obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
 obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o
diff --git a/drivers/watchdog/armada_37xx_wdt.c b/drivers/watchdog/armada_37xx_wdt.c
new file mode 100644
index 000000000000..c43c313ba63d
--- /dev/null
+++ b/drivers/watchdog/armada_37xx_wdt.c
@@ -0,0 +1,387 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Watchdog driver for Marvell Armada 37xx SoCs
+ *
+ * Author: Marek Behun <marek.behun@nic.cz>
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+
+/*
+ * There are four counters that can be used for watchdog on Armada 37xx.
+ * The addresses for counter control registers are register base plus ID*0x10,
+ * where ID is 0, 1, 2 or 3.
+ *
+ * In this driver we use IDs 0 and 1. Counter ID 1 is used as watchdog counter,
+ * while counter ID 0 is used to implement pinging the watchdog: counter ID 1 is
+ * set to restart counting from initial value on counter ID 0 end count event.
+ * Pinging is done by forcing immediate end count event on counter ID 0.
+ * If only one counter was used, pinging would have to be implemented by
+ * disabling and enabling the counter, leaving the system in a vulnerable state
+ * for a (really) short period of time.
+ *
+ * Counters ID 2 and 3 are enabled by default even before U-Boot loads,
+ * therefore this driver does not provide a way to use them, eg. by setting a
+ * property in device tree.
+ */
+
+#define CNTR_ID_RETRIGGER		0
+#define CNTR_ID_WDOG			1
+
+/* relative to cpu_misc */
+#define WDT_TIMER_SELECT		0x64
+#define WDT_TIMER_SELECT_MASK		0xf
+#define WDT_TIMER_SELECT_VAL		BIT(CNTR_ID_WDOG)
+
+/* relative to reg */
+#define CNTR_CTRL(id)			((id) * 0x10)
+#define CNTR_CTRL_ENABLE		0x0001
+#define CNTR_CTRL_ACTIVE		0x0002
+#define CNTR_CTRL_MODE_MASK		0x000c
+#define CNTR_CTRL_MODE_ONESHOT		0x0000
+#define CNTR_CTRL_MODE_HWSIG		0x000c
+#define CNTR_CTRL_TRIG_SRC_MASK		0x00f0
+#define CNTR_CTRL_TRIG_SRC_PREV_CNTR	0x0050
+#define CNTR_CTRL_PRESCALE_MASK		0xff00
+#define CNTR_CTRL_PRESCALE_MIN		2
+#define CNTR_CTRL_PRESCALE_SHIFT	8
+
+#define CNTR_COUNT_LOW(id)		(CNTR_CTRL(id) + 0x4)
+#define CNTR_COUNT_HIGH(id)		(CNTR_CTRL(id) + 0x8)
+
+#define WATCHDOG_TIMEOUT		120
+
+static unsigned int timeout;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+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 armada_37xx_watchdog {
+	struct watchdog_device wdt;
+	struct regmap *cpu_misc;
+	void __iomem *reg;
+	u64 timeout; /* in clock ticks */
+	unsigned long clk_rate;
+	struct clk *clk;
+};
+
+static u64 get_counter_value(struct armada_37xx_watchdog *dev, int id)
+{
+	u64 val;
+
+	/*
+	 * when low is read, high is latched into flip-flops so that it can be
+	 * read consistently without using software debouncing
+	 */
+	val = readl(dev->reg + CNTR_COUNT_LOW(id));
+	val |= ((u64)readl(dev->reg + CNTR_COUNT_HIGH(id))) << 32;
+
+	return val;
+}
+
+static void set_counter_value(struct armada_37xx_watchdog *dev, int id, u64 val)
+{
+	writel(val & 0xffffffff, dev->reg + CNTR_COUNT_LOW(id));
+	writel(val >> 32, dev->reg + CNTR_COUNT_HIGH(id));
+}
+
+static void counter_enable(struct armada_37xx_watchdog *dev, int id)
+{
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL(id));
+	reg |= CNTR_CTRL_ENABLE;
+	writel(reg, dev->reg + CNTR_CTRL(id));
+}
+
+static void counter_disable(struct armada_37xx_watchdog *dev, int id)
+{
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL(id));
+	reg &= ~CNTR_CTRL_ENABLE;
+	writel(reg, dev->reg + CNTR_CTRL(id));
+}
+
+static void init_counter(struct armada_37xx_watchdog *dev, int id, u32 mode,
+			 u32 trig_src)
+{
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL(id));
+
+	reg &= ~(CNTR_CTRL_MODE_MASK | CNTR_CTRL_PRESCALE_MASK |
+		 CNTR_CTRL_TRIG_SRC_MASK);
+
+	/* set mode */
+	reg |= mode & CNTR_CTRL_MODE_MASK;
+
+	/* set prescaler to the min value */
+	reg |= CNTR_CTRL_PRESCALE_MIN << CNTR_CTRL_PRESCALE_SHIFT;
+
+	/* set trigger source */
+	reg |= trig_src & CNTR_CTRL_TRIG_SRC_MASK;
+
+	writel(reg, dev->reg + CNTR_CTRL(id));
+}
+
+static int armada_37xx_wdt_ping(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	/* counter 1 is retriggered by forcing end count on counter 0 */
+	counter_disable(dev, CNTR_ID_RETRIGGER);
+	counter_enable(dev, CNTR_ID_RETRIGGER);
+
+	return 0;
+}
+
+static unsigned int armada_37xx_wdt_get_timeleft(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+	unsigned int res;
+
+	res = get_counter_value(dev, CNTR_ID_WDOG) *
+	      CNTR_CTRL_PRESCALE_MIN / dev->clk_rate;
+
+	return res;
+}
+
+static int armada_37xx_wdt_set_timeout(struct watchdog_device *wdt,
+				       unsigned int timeout)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	wdt->timeout = timeout;
+
+	/*
+	 * Compute the timeout in clock rate. We use smallest possible
+	 * prescaler, which divides the clock rate by 2
+	 * (CNTR_CTRL_PRESCALE_MIN).
+	 */
+	dev->timeout = (u64)dev->clk_rate * timeout / CNTR_CTRL_PRESCALE_MIN;
+
+	return 0;
+}
+
+static bool armada_37xx_wdt_is_running(struct armada_37xx_watchdog *dev)
+{
+	u32 reg;
+
+	regmap_read(dev->cpu_misc, WDT_TIMER_SELECT, &reg);
+	if ((reg & WDT_TIMER_SELECT_MASK) != WDT_TIMER_SELECT_VAL)
+		return false;
+
+	reg = readl(dev->reg + CNTR_CTRL(CNTR_ID_WDOG));
+	return !!(reg & CNTR_CTRL_ACTIVE);
+}
+
+static int armada_37xx_wdt_start(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	/* select counter 1 as watchdog counter */
+	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, WDT_TIMER_SELECT_VAL);
+
+	/* init counter 0 as retrigger counter for counter 1 */
+	init_counter(dev, CNTR_ID_RETRIGGER, CNTR_CTRL_MODE_ONESHOT, 0);
+	set_counter_value(dev, CNTR_ID_RETRIGGER, 0);
+
+	/* init counter 1 to be retriggerable by counter 0 end count */
+	init_counter(dev, CNTR_ID_WDOG, CNTR_CTRL_MODE_HWSIG,
+		     CNTR_CTRL_TRIG_SRC_PREV_CNTR);
+	set_counter_value(dev, CNTR_ID_WDOG, dev->timeout);
+
+	/* enable counter 1 */
+	counter_enable(dev, CNTR_ID_WDOG);
+
+	/* start counter 1 by forcing immediate end count on counter 0 */
+	counter_enable(dev, CNTR_ID_RETRIGGER);
+
+	return 0;
+}
+
+static int armada_37xx_wdt_stop(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	counter_disable(dev, CNTR_ID_WDOG);
+	counter_disable(dev, CNTR_ID_RETRIGGER);
+	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, 0);
+
+	return 0;
+}
+
+static const struct watchdog_info armada_37xx_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.identity = "Armada 37xx Watchdog",
+};
+
+static const struct watchdog_ops armada_37xx_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = armada_37xx_wdt_start,
+	.stop = armada_37xx_wdt_stop,
+	.ping = armada_37xx_wdt_ping,
+	.set_timeout = armada_37xx_wdt_set_timeout,
+	.get_timeleft = armada_37xx_wdt_get_timeleft,
+};
+
+static int armada_37xx_wdt_probe(struct platform_device *pdev)
+{
+	struct armada_37xx_watchdog *dev;
+	struct resource *res;
+	struct regmap *regmap;
+	int ret;
+
+	dev = devm_kzalloc(&pdev->dev, sizeof(struct armada_37xx_watchdog),
+			   GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->wdt.info = &armada_37xx_wdt_info;
+	dev->wdt.ops = &armada_37xx_wdt_ops;
+
+	regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+						 "marvell,system-controller");
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+	dev->cpu_misc = regmap;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+	dev->reg = devm_ioremap(&pdev->dev, res->start, resource_size(res));
+
+	/* init clock */
+	dev->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(dev->clk))
+		return PTR_ERR(dev->clk);
+
+	ret = clk_prepare_enable(dev->clk);
+	if (ret)
+		return ret;
+
+	dev->clk_rate = clk_get_rate(dev->clk);
+	if (!dev->clk_rate) {
+		ret = -EINVAL;
+		goto disable_clk;
+	}
+
+	/*
+	 * Since the timeout in seconds is given as 32 bit unsigned int, and
+	 * the counters hold 64 bit values, even after multiplication by clock
+	 * rate the counter can hold timeout of UINT_MAX seconds.
+	 */
+	dev->wdt.min_timeout = 1;
+	dev->wdt.max_timeout = UINT_MAX;
+	dev->wdt.parent = &pdev->dev;
+
+	/* default value, possibly override by module parameter or dtb */
+	dev->wdt.timeout = WATCHDOG_TIMEOUT;
+	watchdog_init_timeout(&dev->wdt, timeout, &pdev->dev);
+
+	platform_set_drvdata(pdev, &dev->wdt);
+	watchdog_set_drvdata(&dev->wdt, dev);
+
+	armada_37xx_wdt_set_timeout(&dev->wdt, dev->wdt.timeout);
+
+	if (armada_37xx_wdt_is_running(dev))
+		set_bit(WDOG_HW_RUNNING, &dev->wdt.status);
+
+	watchdog_set_nowayout(&dev->wdt, nowayout);
+	ret = watchdog_register_device(&dev->wdt);
+	if (ret)
+		goto disable_clk;
+
+	dev_info(&pdev->dev, "Initial timeout %d sec%s\n",
+		 dev->wdt.timeout, nowayout ? ", nowayout" : "");
+
+	return 0;
+
+disable_clk:
+	clk_disable_unprepare(dev->clk);
+	return ret;
+}
+
+static int armada_37xx_wdt_remove(struct platform_device *pdev)
+{
+	struct watchdog_device *wdt = platform_get_drvdata(pdev);
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	watchdog_unregister_device(wdt);
+	clk_disable_unprepare(dev->clk);
+	return 0;
+}
+
+static void armada_37xx_wdt_shutdown(struct platform_device *pdev)
+{
+	struct watchdog_device *wdt = platform_get_drvdata(pdev);
+
+	armada_37xx_wdt_stop(wdt);
+}
+
+static int __maybe_unused armada_37xx_wdt_suspend(struct device *dev)
+{
+	struct watchdog_device *wdt = dev_get_drvdata(dev);
+
+	return armada_37xx_wdt_stop(wdt);
+}
+
+static int __maybe_unused armada_37xx_wdt_resume(struct device *dev)
+{
+	struct watchdog_device *wdt = dev_get_drvdata(dev);
+
+	if (watchdog_active(wdt))
+		return armada_37xx_wdt_start(wdt);
+
+	return 0;
+}
+
+static const struct dev_pm_ops armada_37xx_wdt_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(armada_37xx_wdt_suspend,
+				armada_37xx_wdt_resume)
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id armada_37xx_wdt_match[] = {
+	{ .compatible = "marvell,armada-3700-wdt", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, armada_37xx_wdt_match);
+#endif
+
+static struct platform_driver armada_37xx_wdt_driver = {
+	.probe		= armada_37xx_wdt_probe,
+	.remove		= armada_37xx_wdt_remove,
+	.shutdown	= armada_37xx_wdt_shutdown,
+	.driver		= {
+		.name	= "armada_37xx_wdt",
+		.of_match_table = of_match_ptr(armada_37xx_wdt_match),
+		.pm = &armada_37xx_wdt_dev_pm_ops,
+	},
+};
+
+module_platform_driver(armada_37xx_wdt_driver);
+
+MODULE_AUTHOR("Marek Behun <marek.behun@nic.cz>");
+MODULE_DESCRIPTION("Armada 37xx CPU Watchdog");
+
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:armada_37xx_wdt");