watchdog: add driver for Cortina Gemini watchdog

This add support for the Cortina systems Gemini (SL3516)
SoC watchdog.

I have tried to use all the right new kernel interfaces
and tested with busybox' "watchdog" command both to kick
and get timeouts and reboots.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/watchdog/Kconfig

@@ -301,6 +301,17 @@ config 977_WATCHDOG
 
 	  Not sure? It's safe to say N.
 
+config GEMINI_WATCHDOG
+	tristate "Gemini watchdog"
+	depends on ARCH_GEMINI
+	select WATCHDOG_CORE
+	help
+	  Say Y here if to include support for the watchdog timer
+	  embedded in the Cortina Systems Gemini family of devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gemini_wdt.
+
 config IXP4XX_WATCHDOG
 	tristate "IXP4xx Watchdog"
 	depends on ARCH_IXP4XX

drivers/watchdog/Makefile

@@ -45,6 +45,7 @@ obj-$(CONFIG_OMAP_WATCHDOG) += omap_wdt.o
 obj-$(CONFIG_TWL4030_WATCHDOG) += twl4030_wdt.o
 obj-$(CONFIG_21285_WATCHDOG) += wdt285.o
 obj-$(CONFIG_977_WATCHDOG) += wdt977.o
+obj-$(CONFIG_GEMINI_WATCHDOG) += gemini_wdt.o
 obj-$(CONFIG_IXP4XX_WATCHDOG) += ixp4xx_wdt.o
 obj-$(CONFIG_KS8695_WATCHDOG) += ks8695_wdt.o
 obj-$(CONFIG_S3C2410_WATCHDOG) += s3c2410_wdt.o

drivers/watchdog/gemini_wdt.c

+/*
+ * Watchdog driver for Cortina Systems Gemini SoC
+ *
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * Inspired by the out-of-tree drivers from OpenWRT:
+ * Copyright (C) 2009 Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bitops.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/watchdog.h>
+
+#define GEMINI_WDCOUNTER	0x0
+#define GEMINI_WDLOAD		0x4
+#define GEMINI_WDRESTART	0x8
+#define GEMINI_WDCR		0xC
+
+#define WDRESTART_MAGIC		0x5AB9
+
+#define WDCR_CLOCK_5MHZ		BIT(4)
+#define WDCR_SYS_RST		BIT(1)
+#define WDCR_ENABLE		BIT(0)
+
+#define WDT_CLOCK		5000000		/* 5 MHz */
+
+struct gemini_wdt {
+	struct watchdog_device	wdd;
+	struct device		*dev;
+	void __iomem		*base;
+};
+
+static inline
+struct gemini_wdt *to_gemini_wdt(struct watchdog_device *wdd)
+{
+	return container_of(wdd, struct gemini_wdt, wdd);
+}
+
+static int gemini_wdt_start(struct watchdog_device *wdd)
+{
+	struct gemini_wdt *gwdt = to_gemini_wdt(wdd);
+
+	writel(wdd->timeout * WDT_CLOCK, gwdt->base + GEMINI_WDLOAD);
+	writel(WDRESTART_MAGIC, gwdt->base + GEMINI_WDRESTART);
+	/* set clock before enabling */
+	writel(WDCR_CLOCK_5MHZ | WDCR_SYS_RST,
+			gwdt->base + GEMINI_WDCR);
+	writel(WDCR_CLOCK_5MHZ | WDCR_SYS_RST | WDCR_ENABLE,
+			gwdt->base + GEMINI_WDCR);
+
+	return 0;
+}
+
+static int gemini_wdt_stop(struct watchdog_device *wdd)
+{
+	struct gemini_wdt *gwdt = to_gemini_wdt(wdd);
+
+	writel(0, gwdt->base + GEMINI_WDCR);
+
+	return 0;
+}
+
+static int gemini_wdt_ping(struct watchdog_device *wdd)
+{
+	struct gemini_wdt *gwdt = to_gemini_wdt(wdd);
+
+	writel(WDRESTART_MAGIC, gwdt->base + GEMINI_WDRESTART);
+
+	return 0;
+}
+
+static int gemini_wdt_set_timeout(struct watchdog_device *wdd,
+				  unsigned int timeout)
+{
+	wdd->timeout = timeout;
+	if (watchdog_active(wdd))
+		gemini_wdt_start(wdd);
+
+	return 0;
+}
+
+static irqreturn_t gemini_wdt_interrupt(int irq, void *data)
+{
+	struct gemini_wdt *gwdt = data;
+
+	watchdog_notify_pretimeout(&gwdt->wdd);
+
+	return IRQ_HANDLED;
+}
+
+static const struct watchdog_ops gemini_wdt_ops = {
+	.start		= gemini_wdt_start,
+	.stop		= gemini_wdt_stop,
+	.ping		= gemini_wdt_ping,
+	.set_timeout	= gemini_wdt_set_timeout,
+	.owner		= THIS_MODULE,
+};
+
+static const struct watchdog_info gemini_wdt_info = {
+	.options	= WDIOF_KEEPALIVEPING
+			| WDIOF_MAGICCLOSE
+			| WDIOF_SETTIMEOUT,
+	.identity	= KBUILD_MODNAME,
+};
+
+
+static int gemini_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	struct gemini_wdt *gwdt;
+	unsigned int reg;
+	int irq;
+	int ret;
+
+	gwdt = devm_kzalloc(dev, sizeof(*gwdt), GFP_KERNEL);
+	if (!gwdt)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	gwdt->base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(gwdt->base))
+		return PTR_ERR(gwdt->base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (!irq)
+		return -EINVAL;
+
+	gwdt->dev = dev;
+	gwdt->wdd.info = &gemini_wdt_info;
+	gwdt->wdd.ops = &gemini_wdt_ops;
+	gwdt->wdd.min_timeout = 1;
+	gwdt->wdd.max_timeout = 0xFFFFFFFF / WDT_CLOCK;
+	gwdt->wdd.parent = dev;
+
+	/*
+	 * If 'timeout-sec' unspecified in devicetree, assume a 13 second
+	 * default.
+	 */
+	gwdt->wdd.timeout = 13U;
+	watchdog_init_timeout(&gwdt->wdd, 0, dev);
+
+	reg = readw(gwdt->base + GEMINI_WDCR);
+	if (reg & WDCR_ENABLE) {
+		/* Watchdog was enabled by the bootloader, disable it. */
+		reg &= ~WDCR_ENABLE;
+		writel(reg, gwdt->base + GEMINI_WDCR);
+	}
+
+	ret = devm_request_irq(dev, irq, gemini_wdt_interrupt, 0,
+			       "watchdog bark", gwdt);
+	if (ret)
+		return ret;
+
+	ret = devm_watchdog_register_device(dev, &gwdt->wdd);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register watchdog\n");
+		return ret;
+	}
+
+	/* Set up platform driver data */
+	platform_set_drvdata(pdev, gwdt);
+	dev_info(dev, "Gemini watchdog driver enabled\n");
+
+	return 0;
+}
+
+static int __maybe_unused gemini_wdt_suspend(struct device *dev)
+{
+	struct gemini_wdt *gwdt = dev_get_drvdata(dev);
+	unsigned int reg;
+
+	reg = readw(gwdt->base + GEMINI_WDCR);
+	reg &= ~WDCR_ENABLE;
+	writel(reg, gwdt->base + GEMINI_WDCR);
+
+	return 0;
+}
+
+static int __maybe_unused gemini_wdt_resume(struct device *dev)
+{
+	struct gemini_wdt *gwdt = dev_get_drvdata(dev);
+	unsigned int reg;
+
+	if (watchdog_active(&gwdt->wdd)) {
+		reg = readw(gwdt->base + GEMINI_WDCR);
+		reg |= WDCR_ENABLE;
+		writel(reg, gwdt->base + GEMINI_WDCR);
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops gemini_wdt_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(gemini_wdt_suspend,
+				gemini_wdt_resume)
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id gemini_wdt_match[] = {
+	{ .compatible = "cortina,gemini-watchdog" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, gemini_wdt_match);
+#endif
+
+static struct platform_driver gemini_wdt_driver = {
+	.probe		= gemini_wdt_probe,
+	.driver		= {
+		.name	= "gemini-wdt",
+		.of_match_table = of_match_ptr(gemini_wdt_match),
+		.pm = &gemini_wdt_dev_pm_ops,
+	},
+};
+module_platform_driver(gemini_wdt_driver);
+MODULE_AUTHOR("Linus Walleij");
+MODULE_DESCRIPTION("Watchdog driver for Gemini");
+MODULE_LICENSE("GPL");