watchdog: add MT7621 watchdog support

This patch adds support for the watchdog core found on newer MediaTek Wifi
SoCs MT7621 and MT7628. There is no symbol for MT7628 as it is a subtype of
MT7620 so we depend on that instead.
Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Documentation/devicetree/bindings/watchdog/mt7621-wdt.txt

+Ralink Watchdog Timers
+
+Required properties:
+- compatible: must be "mediatek,mt7621-wdt"
+- reg: physical base address of the controller and length of the register range
+
+Example:
+
+	watchdog@100 {
+		compatible = "mediatek,mt7621-wdt";
+		reg = <0x100 0x10>;
+	};

drivers/watchdog/Kconfig

@@ -1403,6 +1403,13 @@ config RALINK_WDT
 	help
 	  Hardware driver for the Ralink SoC Watchdog Timer.
 
+config MT7621_WDT
+	tristate "Mediatek SoC watchdog"
+	select WATCHDOG_CORE
+	depends on SOC_MT7620 || SOC_MT7621
+	help
+	  Hardware driver for the Mediatek/Ralink MT7621/8 SoC Watchdog Timer.
+
 # PARISC Architecture
 
 # POWERPC Architecture

drivers/watchdog/Makefile

@@ -152,6 +152,7 @@ octeon-wdt-y := octeon-wdt-main.o octeon-wdt-nmi.o
 obj-$(CONFIG_LANTIQ_WDT) += lantiq_wdt.o
 obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
 obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
+obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
 
 # PARISC Architecture
 

drivers/watchdog/mt7621_wdt.c

+/*
+ * Ralink MT7621/MT7628 built-in hardware watchdog timer
+ *
+ * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
+ *
+ * This driver was based on: drivers/watchdog/rt2880_wdt.c
+ *
+ * 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/clk.h>
+#include <linux/reset.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/watchdog.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+
+#include <asm/mach-ralink/ralink_regs.h>
+
+#define SYSC_RSTSTAT			0x38
+#define WDT_RST_CAUSE			BIT(1)
+
+#define RALINK_WDT_TIMEOUT		30
+
+#define TIMER_REG_TMRSTAT		0x00
+#define TIMER_REG_TMR1LOAD		0x24
+#define TIMER_REG_TMR1CTL		0x20
+
+#define TMR1CTL_ENABLE			BIT(7)
+#define TMR1CTL_RESTART			BIT(9)
+#define TMR1CTL_PRESCALE_SHIFT		16
+
+static void __iomem *mt7621_wdt_base;
+static struct reset_control *mt7621_wdt_reset;
+
+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 inline void rt_wdt_w32(unsigned reg, u32 val)
+{
+	iowrite32(val, mt7621_wdt_base + reg);
+}
+
+static inline u32 rt_wdt_r32(unsigned reg)
+{
+	return ioread32(mt7621_wdt_base + reg);
+}
+
+static int mt7621_wdt_ping(struct watchdog_device *w)
+{
+	rt_wdt_w32(TIMER_REG_TMRSTAT, TMR1CTL_RESTART);
+
+	return 0;
+}
+
+static int mt7621_wdt_set_timeout(struct watchdog_device *w, unsigned int t)
+{
+	w->timeout = t;
+	rt_wdt_w32(TIMER_REG_TMR1LOAD, t * 1000);
+	mt7621_wdt_ping(w);
+
+	return 0;
+}
+
+static int mt7621_wdt_start(struct watchdog_device *w)
+{
+	u32 t;
+
+	/* set the prescaler to 1ms == 1000us */
+	rt_wdt_w32(TIMER_REG_TMR1CTL, 1000 << TMR1CTL_PRESCALE_SHIFT);
+
+	mt7621_wdt_set_timeout(w, w->timeout);
+
+	t = rt_wdt_r32(TIMER_REG_TMR1CTL);
+	t |= TMR1CTL_ENABLE;
+	rt_wdt_w32(TIMER_REG_TMR1CTL, t);
+
+	return 0;
+}
+
+static int mt7621_wdt_stop(struct watchdog_device *w)
+{
+	u32 t;
+
+	mt7621_wdt_ping(w);
+
+	t = rt_wdt_r32(TIMER_REG_TMR1CTL);
+	t &= ~TMR1CTL_ENABLE;
+	rt_wdt_w32(TIMER_REG_TMR1CTL, t);
+
+	return 0;
+}
+
+static int mt7621_wdt_bootcause(void)
+{
+	if (rt_sysc_r32(SYSC_RSTSTAT) & WDT_RST_CAUSE)
+		return WDIOF_CARDRESET;
+
+	return 0;
+}
+
+static struct watchdog_info mt7621_wdt_info = {
+	.identity = "Mediatek Watchdog",
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+};
+
+static struct watchdog_ops mt7621_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = mt7621_wdt_start,
+	.stop = mt7621_wdt_stop,
+	.ping = mt7621_wdt_ping,
+	.set_timeout = mt7621_wdt_set_timeout,
+};
+
+static struct watchdog_device mt7621_wdt_dev = {
+	.info = &mt7621_wdt_info,
+	.ops = &mt7621_wdt_ops,
+	.min_timeout = 1,
+	.max_timeout = 0xfffful / 1000,
+};
+
+static int mt7621_wdt_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	int ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mt7621_wdt_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(mt7621_wdt_base))
+		return PTR_ERR(mt7621_wdt_base);
+
+	mt7621_wdt_reset = devm_reset_control_get(&pdev->dev, NULL);
+	if (!IS_ERR(mt7621_wdt_reset))
+		reset_control_deassert(mt7621_wdt_reset);
+
+	mt7621_wdt_dev.dev = &pdev->dev;
+	mt7621_wdt_dev.bootstatus = mt7621_wdt_bootcause();
+
+	watchdog_init_timeout(&mt7621_wdt_dev, mt7621_wdt_dev.max_timeout,
+			      &pdev->dev);
+	watchdog_set_nowayout(&mt7621_wdt_dev, nowayout);
+
+	ret = watchdog_register_device(&mt7621_wdt_dev);
+
+	return 0;
+}
+
+static int mt7621_wdt_remove(struct platform_device *pdev)
+{
+	watchdog_unregister_device(&mt7621_wdt_dev);
+
+	return 0;
+}
+
+static void mt7621_wdt_shutdown(struct platform_device *pdev)
+{
+	mt7621_wdt_stop(&mt7621_wdt_dev);
+}
+
+static const struct of_device_id mt7621_wdt_match[] = {
+	{ .compatible = "mediatek,mt7621-wdt" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mt7621_wdt_match);
+
+static struct platform_driver mt7621_wdt_driver = {
+	.probe		= mt7621_wdt_probe,
+	.remove		= mt7621_wdt_remove,
+	.shutdown	= mt7621_wdt_shutdown,
+	.driver		= {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= mt7621_wdt_match,
+	},
+};
+
+module_platform_driver(mt7621_wdt_driver);
+
+MODULE_DESCRIPTION("MediaTek MT762x hardware watchdog driver");
+MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
+MODULE_LICENSE("GPL v2");