[PATCH 2/3] watchdog: sam9x60_wdt: introduce sam9x60 watchdog timer driver

[<Eugen.Hristev@microchip.com>]

From: Eugen Hristev <eugen.hristev@microchip.com>

This is the driver for SAM9X60 watchdog timer.
The offered functionality is the same as sama5d4_wdt.
The difference comes in register map, way to configure the timeout and
interrupts.
Developed starting from sama5d4_wdt.c

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
 drivers/watchdog/Kconfig       |   9 ++
 drivers/watchdog/Makefile      |   1 +
 drivers/watchdog/sam9x60_wdt.c | 335 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 345 insertions(+)
 create mode 100644 drivers/watchdog/sam9x60_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 58e7c10..3562e26 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -416,6 +416,15 @@ config SAMA5D4_WATCHDOG
 	  Its Watchdog Timer Mode Register can be written more than once.
 	  This will reboot your system when the timeout is reached.
 
+config SAM9X60_WATCHDOG
+	tristate "Microchip SAM9X60 Watchdog Timer"
+	depends on ARCH_AT91 || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Microchip SAM9X60 watchdog timer is embedded into SAM9X60 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
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee352b..93ba599 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_IXP4XX_WATCHDOG) += ixp4xx_wdt.o
 obj-$(CONFIG_S3C2410_WATCHDOG) += s3c2410_wdt.o
 obj-$(CONFIG_SA1100_WATCHDOG) += sa1100_wdt.o
 obj-$(CONFIG_SAMA5D4_WATCHDOG) += sama5d4_wdt.o
+obj-$(CONFIG_SAM9X60_WATCHDOG) += sam9x60_wdt.o
 obj-$(CONFIG_DW_WATCHDOG) += dw_wdt.o
 obj-$(CONFIG_EP93XX_WATCHDOG) += ep93xx_wdt.o
 obj-$(CONFIG_PNX4008_WATCHDOG) += pnx4008_wdt.o
diff --git a/drivers/watchdog/sam9x60_wdt.c b/drivers/watchdog/sam9x60_wdt.c
new file mode 100644
index 00000000..f612230
--- /dev/null
+++ b/drivers/watchdog/sam9x60_wdt.c
@@ -0,0 +1,335 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Microchip SAM9X60 Watchdog Timer
+ *
+ * Copyright (C) 2019 Microchip Technology, Inc.
+ * Author: Eugen Hristev <eugen.hristev@microchip.com>
+ *
+ */
+
+#include <linux/delay.h>
+#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>
+
+#define AT91_WDT_CR		0x00			/* Watchdog Control Register */
+#define		AT91_WDT_WDRSTT		BIT(0)		/* Restart */
+#define		AT91_WDT_KEY		(0xa5 << 24)		/* KEY Password */
+
+#define AT91_WDT_MR		0x04			/* Watchdog Mode Register */
+#define		AT91_WDT_PERIODRST	BIT(4)		/* Period Reset */
+#define		AT91_WDT_RPTHRST	BIT(5)		/* Minimum Restart Period */
+#define		AT91_WDT_WDDIS		BIT(12)		/* Disable */
+#define		AT91_WDT_WDDBGHLT	BIT(28)		/* Debug Halt */
+#define		AT91_WDT_WDIDLEHLT	BIT(29)		/* Idle Halt */
+
+#define AT91_WDT_VR		0x08			/* Watchdog Timer Value Register */
+
+#define AT91_WDT_WLR		0x0c
+#define		AT91_WDT_COUNTER	(0xfff << 0)		/* Watchdog Period Value */
+#define		AT91_WDT_SET_COUNTER(x)	((x) & AT91_WDT_COUNTER)
+
+#define AT91_WDT_IER		0x14			/* Interrupt Enable Register */
+#define		AT91_WDT_PERINT		BIT(0)		/* Period Interrupt Enable */
+#define AT91_WDT_IDR		0x18			/* Interrupt Disable Register */
+#define AT91_WDT_ISR		0x1c			/* Interrupt Status Register */
+
+/* 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 sam9x60_wdt {
+	struct watchdog_device	wdd;
+	void __iomem		*reg_base;
+	u32			mr;
+	u32			ir;
+	unsigned long		last_ping;
+};
+
+static int wdt_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_enabled (!(wdt->mr & AT91_WDT_WDDIS))
+
+#define wdt_read(wdt, field) \
+	readl_relaxed((wdt)->reg_base + (field))
+
+/* 4 slow clock periods is 4/32768 = 122.07us*/
+#define WDT_DELAY	usecs_to_jiffies(123)
+
+static void wdt_write(struct sam9x60_wdt *wdt, u32 field, u32 val)
+{
+	/*
+	 * WDT_CR and WDT_MR must not be modified within three slow clock
+	 * periods following a restart of the watchdog performed by a write
+	 * access in WDT_CR.
+	 */
+	while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
+		usleep_range(30, 125);
+	writel_relaxed(val, wdt->reg_base + field);
+	wdt->last_ping = jiffies;
+}
+
+static void wdt_write_nosleep(struct sam9x60_wdt *wdt, u32 field, u32 val)
+{
+	if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
+		usleep_range(123, 250);
+	writel_relaxed(val, wdt->reg_base + field);
+	wdt->last_ping = jiffies;
+}
+
+static int sam9x60_wdt_start(struct watchdog_device *wdd)
+{
+	struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdt->mr &= ~AT91_WDT_WDDIS;
+	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
+	wdt_write_nosleep(wdt, AT91_WDT_IER, wdt->ir);
+
+	return 0;
+}
+
+static int sam9x60_wdt_stop(struct watchdog_device *wdd)
+{
+	struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdt->mr |= AT91_WDT_WDDIS;
+	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
+	wdt_write_nosleep(wdt, AT91_WDT_IDR, wdt->ir);
+
+	return 0;
+}
+
+static int sam9x60_wdt_ping(struct watchdog_device *wdd)
+{
+	struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
+
+	return 0;
+}
+
+static int sam9x60_wdt_set_timeout(struct watchdog_device *wdd,
+				   unsigned int timeout)
+{
+	struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdt_write(wdt, AT91_WDT_WLR,
+		  AT91_WDT_SET_COUNTER(WDT_SEC2TICKS(timeout)));
+
+	wdd->timeout = timeout;
+
+	return 0;
+}
+
+static const struct watchdog_info sam9x60_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+	.identity = "Microchip SAM9X60 Watchdog",
+};
+
+static const struct watchdog_ops sam9x60_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = sam9x60_wdt_start,
+	.stop = sam9x60_wdt_stop,
+	.ping = sam9x60_wdt_ping,
+	.set_timeout = sam9x60_wdt_set_timeout,
+};
+
+static irqreturn_t sam9x60_wdt_irq_handler(int irq, void *dev_id)
+{
+	struct sam9x60_wdt *wdt = platform_get_drvdata(dev_id);
+
+	if (wdt_read(wdt, AT91_WDT_ISR)) {
+		pr_crit("Microchip Watchdog Software Reset\n");
+		emergency_restart();
+		pr_crit("Reboot didn't succeed\n");
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int of_sam9x60_wdt_init(struct device_node *np, struct sam9x60_wdt *wdt)
+{
+	const char *tmp;
+
+	wdt->mr = AT91_WDT_WDDIS;
+
+	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
+	    !strcmp(tmp, "software"))
+		wdt->ir = AT91_WDT_PERINT;
+	else
+		wdt->mr |= AT91_WDT_PERIODRST;
+
+	if (of_property_read_bool(np, "atmel,idle-halt"))
+		wdt->mr |= AT91_WDT_WDIDLEHLT;
+
+	if (of_property_read_bool(np, "atmel,dbg-halt"))
+		wdt->mr |= AT91_WDT_WDDBGHLT;
+
+	return 0;
+}
+
+static int sam9x60_wdt_init(struct sam9x60_wdt *wdt)
+{
+	u32 reg;
+	/*
+	 * When booting and resuming, the bootloader may have changed the
+	 * watchdog configuration.
+	 * If the watchdog is already running, we can safely update it.
+	 * Else, we have to disable it properly.
+	 */
+	if (wdt_enabled) {
+		wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
+		wdt_write_nosleep(wdt, AT91_WDT_IER, wdt->ir);
+		wdt_write(wdt, AT91_WDT_WLR,
+			  AT91_WDT_SET_COUNTER(WDT_SEC2TICKS(WDT_DEFAULT_TIMEOUT)));
+
+	} else {
+		reg = wdt_read(wdt, AT91_WDT_MR);
+		if (!(reg & AT91_WDT_WDDIS))
+			wdt_write_nosleep(wdt, AT91_WDT_MR,
+					  reg | AT91_WDT_WDDIS);
+	}
+	return 0;
+}
+
+static int sam9x60_wdt_probe(struct platform_device *pdev)
+{
+	struct watchdog_device *wdd;
+	struct sam9x60_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_DEFAULT_TIMEOUT;
+	wdd->info = &sam9x60_wdt_info;
+	wdd->ops = &sam9x60_wdt_ops;
+	wdd->min_timeout = MIN_WDT_TIMEOUT;
+	wdd->max_timeout = MAX_WDT_TIMEOUT;
+	wdt->last_ping = jiffies;
+
+	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;
+
+	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_sam9x60_wdt_init(pdev->dev.of_node, wdt);
+	if (ret)
+		return ret;
+
+	if ((wdt->ir & AT91_WDT_PERINT) && irq) {
+		ret = devm_request_irq(&pdev->dev, irq, sam9x60_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;
+		}
+	}
+
+	watchdog_init_timeout(wdd, wdt_timeout, &pdev->dev);
+
+	ret = sam9x60_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",
+		 wdd->timeout, nowayout);
+
+	return 0;
+}
+
+static int sam9x60_wdt_remove(struct platform_device *pdev)
+{
+	struct sam9x60_wdt *wdt = platform_get_drvdata(pdev);
+
+	sam9x60_wdt_stop(&wdt->wdd);
+
+	watchdog_unregister_device(&wdt->wdd);
+
+	return 0;
+}
+
+static const struct of_device_id sam9x60_wdt_of_match[] = {
+	{ .compatible = "microchip,sam9x60-wdt", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sam9x60_wdt_of_match);
+
+#ifdef CONFIG_PM_SLEEP
+static int sam9x60_wdt_resume(struct device *dev)
+{
+	struct sam9x60_wdt *wdt = dev_get_drvdata(dev);
+
+	/*
+	 * FIXME: writing MR also pings the watchdog which may not be desired.
+	 * This should only be done when the registers are lost on suspend but
+	 * there is no way to get this information right now.
+	 */
+	sam9x60_wdt_init(wdt);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(sam9x60_wdt_pm_ops, NULL,
+			 sam9x60_wdt_resume);
+
+static struct platform_driver sam9x60_wdt_driver = {
+	.probe		= sam9x60_wdt_probe,
+	.remove		= sam9x60_wdt_remove,
+	.driver		= {
+		.name	= "sam9x60_wdt",
+		.pm	= &sam9x60_wdt_pm_ops,
+		.of_match_table = sam9x60_wdt_of_match,
+	}
+};
+module_platform_driver(sam9x60_wdt_driver);
+
+MODULE_AUTHOR("Eugen Hristev");
+MODULE_DESCRIPTION("Microchip SAM9X60 Watchdog Timer driver");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4