[PATCH v1 4/7] watchdog: Add support for Armada 37xx CPU watchdog

[marek.behun@nic.cz (Marek Behún)]

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)
(Marvell's Linux also uses second counter by default).
In the future it could be adapted to use other counters, with
definition in the device tree.

Signed-off-by: Marek Behun <marek.behun@nic.cz>
Tested-by: Gregory CLEMENT <gregory.clement@bootlin.com>

 create mode 100644 Documentation/devicetree/bindings/watchdog/armada-37xx-wdt.txt
 create mode 100644 drivers/watchdog/armada_37xx_wdt.c

diff --git a/Documentation/devicetree/bindings/watchdog/armada-37xx-wdt.txt b/Documentation/devicetree/bindings/watchdog/armada-37xx-wdt.txt
new file mode 100644
index 000000000000..4ba9e40ad386
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/armada-37xx-wdt.txt
@@ -0,0 +1,23 @@
+* Armada 37xx CPU Watchdog Timer Controller
+
+Required properties:
+- compatible : must be "marvell,armada-3700-wdt"
+- reg : base physical address of the controller and length of memory mapped
+	region.
+- clocks : the clock feeding the watchdog timer. See clock-bindings.txt
+- marvell,system-controller : reference to syscon node for the CPU Miscellaneous
+	Registers
+
+Example:
+
+	cpu_misc: system-controller at d000 {
+		compatible = "syscon", "simple-mfd";
+		reg = <0xd000 0x1000>;
+	};
+
+	wdt: watchdog-timer at 8300 {
+		compatible = "marvell,armada-3700-wdt";
+		reg = <0x8300 0x40>;
+		marvell,system-controller = <&cpu_misc>;
+		clocks = <&xtalclk>;
+	};
diff --git a/MAINTAINERS b/MAINTAINERS
index cfac1b21596c..e2d2955a8331 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1385,6 +1385,7 @@ S:	Maintained
 F:	include/mfd/moxtet.h
 F:	drivers/gpio/gpio-moxtet-sfp.c
 F:	drivers/mfd/moxtet.c
+F:	drivers/watchdog/armada_37xx_wdt.c
 
 ARM/EBSA110 MACHINE SUPPORT
 M:	Russell King <linux@armlinux.org.uk>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 9af07fd92763..c3d82e3fe1e1 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -263,6 +263,17 @@ 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 1d3c6b094fe5..476d9069ed7c 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..83ba4ce40d2f
--- /dev/null
+++ b/drivers/watchdog/armada_37xx_wdt.c
@@ -0,0 +1,353 @@
+// 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 ID 1. Marvell's Linux also uses this ID by default,
+ * and the U-Boot driver written simultaneosly by the same author as this
+ * driver also uses ID 1.
+ * Maybe in the future we could change this driver to support other counters,
+ * depending on the device tree, but I don't think this is necessary.
+ *
+ * Note that CNTR_ID cannot be 3, because the third counter is an increment
+ * counter, and this driver is written to support decrementing counters only.
+ */
+
+/* relative to cpu_misc */
+#define WDT_TIMER_SELECT		0x64
+#define WDT_TIMER_SELECT_MASK		0xf
+#define WDT_TIMER_SELECT_VAL		BIT(CNTR_ID)
+
+/* relative to reg */
+#define CNTR_ID				1
+
+#define CNTR_CTRL			(CNTR_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_PRESCALE_MASK		0xff00
+#define CNTR_CTRL_PRESCALE_MIN		2
+#define CNTR_CTRL_PRESCALE_SHIFT	8
+
+#define CNTR_COUNT_LOW			(CNTR_CTRL + 0x4)
+#define CNTR_COUNT_HIGH			(CNTR_CTRL + 0x8)
+
+#define WATCHDOG_TIMEOUT		120
+
+static unsigned int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
+			  __MODULE_STRING(WATCHDOG_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 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)
+{
+	u64 val;
+
+	val = readl(dev->reg + CNTR_COUNT_HIGH);
+	val = (val << 32) | readl(dev->reg + CNTR_COUNT_LOW);
+
+	return val;
+}
+
+static void set_counter_value(struct armada_37xx_watchdog *dev)
+{
+	writel(dev->timeout & 0xffffffff, dev->reg + CNTR_COUNT_LOW);
+	writel(dev->timeout >> 32, dev->reg + CNTR_COUNT_HIGH);
+}
+
+static void armada_37xx_wdt_counter_enable(struct armada_37xx_watchdog *dev)
+{
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL);
+	reg |= CNTR_CTRL_ENABLE;
+	writel(reg, dev->reg + CNTR_CTRL);
+}
+
+static void armada_37xx_wdt_counter_disable(struct armada_37xx_watchdog *dev)
+{
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL);
+	reg &= ~CNTR_CTRL_ENABLE;
+	writel(reg, dev->reg + CNTR_CTRL);
+}
+
+static int armada_37xx_wdt_ping(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	armada_37xx_wdt_counter_disable(dev);
+	set_counter_value(dev);
+	armada_37xx_wdt_counter_enable(dev);
+
+	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_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);
+	return !!(reg & CNTR_CTRL_ACTIVE);
+}
+
+static int armada_37xx_wdt_start(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+	u32 reg;
+
+	reg = readl(dev->reg + CNTR_CTRL);
+
+	if (reg & CNTR_CTRL_ACTIVE)
+		return -EBUSY;
+
+	/* set mode */
+	reg = (reg & ~CNTR_CTRL_MODE_MASK) | CNTR_CTRL_MODE_ONESHOT;
+
+	/* set prescaler to the min value of 2 */
+	reg &= ~CNTR_CTRL_PRESCALE_MASK;
+	reg |= CNTR_CTRL_PRESCALE_MIN << CNTR_CTRL_PRESCALE_SHIFT;
+
+	writel(reg, dev->reg + CNTR_CTRL);
+
+	set_counter_value(dev);
+
+	regmap_write(dev->cpu_misc, WDT_TIMER_SELECT, WDT_TIMER_SELECT_VAL);
+	armada_37xx_wdt_counter_enable(dev);
+
+	return 0;
+}
+
+static int armada_37xx_wdt_stop(struct watchdog_device *wdt)
+{
+	struct armada_37xx_watchdog *dev = watchdog_get_drvdata(wdt);
+
+	armada_37xx_wdt_counter_disable(dev);
+	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;
+	dev->wdt.min_timeout = 1;
+
+	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);
+
+	/*
+	 * 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 = 0;
+	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);
+	else
+		armada_37xx_wdt_stop(&dev->wdt);
+
+	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");
-- 
2.16.4