1/*
  2 * Watchdog driver for Broadcom BCM2835
  3 *
  4 * "bcm2708_wdog" driver written by Luke Diamand that was obtained from
  5 * branch "rpi-3.6.y" of git://github.com/raspberrypi/linux.git was used
  6 * as a hardware reference for the Broadcom BCM2835 watchdog timer.
  7 *
  8 * Copyright (C) 2013 Lubomir Rintel <lkundrak@v3.sk>
  9 *
 10 * This program is free software; you can redistribute it and/or modify it
 11 * under the terms of the GNU General Public License as published by the
 12 * Free Software Foundation; either version 2 of the License, or (at your
 13 * option) any later version.
 14 */
 15
 16#include <linux/delay.h>
 17#include <linux/reboot.h>
 18#include <linux/types.h>
 19#include <linux/module.h>
 20#include <linux/io.h>
 21#include <linux/watchdog.h>
 22#include <linux/platform_device.h>
 23#include <linux/of_address.h>
 24#include <linux/of_platform.h>
 25
 26#define PM_RSTC				0x1c
 27#define PM_RSTS				0x20
 28#define PM_WDOG				0x24
 29
 30#define PM_PASSWORD			0x5a000000
 31
 32#define PM_WDOG_TIME_SET		0x000fffff
 33#define PM_RSTC_WRCFG_CLR		0xffffffcf
 34#define PM_RSTS_HADWRH_SET		0x00000040
 35#define PM_RSTC_WRCFG_SET		0x00000030
 36#define PM_RSTC_WRCFG_FULL_RESET	0x00000020
 37#define PM_RSTC_RESET			0x00000102
 38
 39/*
 40 * The Raspberry Pi firmware uses the RSTS register to know which partiton
 41 * to boot from. The partiton value is spread into bits 0, 2, 4, 6, 8, 10.
 42 * Partiton 63 is a special partition used by the firmware to indicate halt.
 43 */
 44#define PM_RSTS_RASPBERRYPI_HALT	0x555
 45
 46#define SECS_TO_WDOG_TICKS(x) ((x) << 16)
 47#define WDOG_TICKS_TO_SECS(x) ((x) >> 16)
 48
 49struct bcm2835_wdt {
 50	void __iomem		*base;
 51	spinlock_t		lock;
 52	struct notifier_block	restart_handler;
 53};
 54
 55static unsigned int heartbeat;
 56static bool nowayout = WATCHDOG_NOWAYOUT;
 57
 58static int bcm2835_wdt_start(struct watchdog_device *wdog)
 59{
 60	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
 61	uint32_t cur;
 62	unsigned long flags;
 63
 64	spin_lock_irqsave(&wdt->lock, flags);
 65
 66	writel_relaxed(PM_PASSWORD | (SECS_TO_WDOG_TICKS(wdog->timeout) &
 67				PM_WDOG_TIME_SET), wdt->base + PM_WDOG);
 68	cur = readl_relaxed(wdt->base + PM_RSTC);
 69	writel_relaxed(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) |
 70		  PM_RSTC_WRCFG_FULL_RESET, wdt->base + PM_RSTC);
 71
 72	spin_unlock_irqrestore(&wdt->lock, flags);
 73
 74	return 0;
 75}
 76
 77static int bcm2835_wdt_stop(struct watchdog_device *wdog)
 78{
 79	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
 80
 81	writel_relaxed(PM_PASSWORD | PM_RSTC_RESET, wdt->base + PM_RSTC);
 82	return 0;
 83}
 84
 85static int bcm2835_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
 86{
 87	wdog->timeout = t;
 88	return 0;
 89}
 90
 91static unsigned int bcm2835_wdt_get_timeleft(struct watchdog_device *wdog)
 92{
 93	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
 94
 95	uint32_t ret = readl_relaxed(wdt->base + PM_WDOG);
 96	return WDOG_TICKS_TO_SECS(ret & PM_WDOG_TIME_SET);
 97}
 98
 99static struct watchdog_ops bcm2835_wdt_ops = {
100	.owner =	THIS_MODULE,
101	.start =	bcm2835_wdt_start,
102	.stop =		bcm2835_wdt_stop,
103	.set_timeout =	bcm2835_wdt_set_timeout,
104	.get_timeleft =	bcm2835_wdt_get_timeleft,
105};
106
107static struct watchdog_info bcm2835_wdt_info = {
108	.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
109			WDIOF_KEEPALIVEPING,
110	.identity =	"Broadcom BCM2835 Watchdog timer",
111};
112
113static struct watchdog_device bcm2835_wdt_wdd = {
114	.info =		&bcm2835_wdt_info,
115	.ops =		&bcm2835_wdt_ops,
116	.min_timeout =	1,
117	.max_timeout =	WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
118	.timeout =	WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
119};
120
121static int
122bcm2835_restart(struct notifier_block *this, unsigned long mode, void *cmd)
123{
124	struct bcm2835_wdt *wdt = container_of(this, struct bcm2835_wdt,
125					       restart_handler);
126	u32 val;
127
128	/* use a timeout of 10 ticks (~150us) */
129	writel_relaxed(10 | PM_PASSWORD, wdt->base + PM_WDOG);
130	val = readl_relaxed(wdt->base + PM_RSTC);
131	val &= PM_RSTC_WRCFG_CLR;
132	val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
133	writel_relaxed(val, wdt->base + PM_RSTC);
134
135	/* No sleeping, possibly atomic. */
136	mdelay(1);
137
138	return 0;
139}
140
141/*
142 * We can't really power off, but if we do the normal reset scheme, and
143 * indicate to bootcode.bin not to reboot, then most of the chip will be
144 * powered off.
145 */
146static void bcm2835_power_off(void)
147{
148	struct device_node *np =
149		of_find_compatible_node(NULL, NULL, "brcm,bcm2835-pm-wdt");
150	struct platform_device *pdev = of_find_device_by_node(np);
151	struct bcm2835_wdt *wdt = platform_get_drvdata(pdev);
152	u32 val;
153
154	/*
155	 * We set the watchdog hard reset bit here to distinguish this reset
156	 * from the normal (full) reset. bootcode.bin will not reboot after a
157	 * hard reset.
158	 */
159	val = readl_relaxed(wdt->base + PM_RSTS);
160	val |= PM_PASSWORD | PM_RSTS_RASPBERRYPI_HALT;
161	writel_relaxed(val, wdt->base + PM_RSTS);
162
163	/* Continue with normal reset mechanism */
164	bcm2835_restart(&wdt->restart_handler, REBOOT_HARD, NULL);
165}
166
167static int bcm2835_wdt_probe(struct platform_device *pdev)
168{
169	struct device *dev = &pdev->dev;
170	struct device_node *np = dev->of_node;
171	struct bcm2835_wdt *wdt;
172	int err;
173
174	wdt = devm_kzalloc(dev, sizeof(struct bcm2835_wdt), GFP_KERNEL);
175	if (!wdt)
176		return -ENOMEM;
177	platform_set_drvdata(pdev, wdt);
178
179	spin_lock_init(&wdt->lock);
180
181	wdt->base = of_iomap(np, 0);
182	if (!wdt->base) {
183		dev_err(dev, "Failed to remap watchdog regs");
184		return -ENODEV;
185	}
186
187	watchdog_set_drvdata(&bcm2835_wdt_wdd, wdt);
188	watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
189	watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
190	bcm2835_wdt_wdd.parent = &pdev->dev;
191	err = watchdog_register_device(&bcm2835_wdt_wdd);
192	if (err) {
193		dev_err(dev, "Failed to register watchdog device");
194		iounmap(wdt->base);
195		return err;
196	}
197
198	wdt->restart_handler.notifier_call = bcm2835_restart;
199	wdt->restart_handler.priority = 128;
200	register_restart_handler(&wdt->restart_handler);
201	if (pm_power_off == NULL)
202		pm_power_off = bcm2835_power_off;
203
204	dev_info(dev, "Broadcom BCM2835 watchdog timer");
205	return 0;
206}
207
208static int bcm2835_wdt_remove(struct platform_device *pdev)
209{
210	struct bcm2835_wdt *wdt = platform_get_drvdata(pdev);
211
212	unregister_restart_handler(&wdt->restart_handler);
213	if (pm_power_off == bcm2835_power_off)
214		pm_power_off = NULL;
215	watchdog_unregister_device(&bcm2835_wdt_wdd);
216	iounmap(wdt->base);
217
218	return 0;
219}
220
221static void bcm2835_wdt_shutdown(struct platform_device *pdev)
222{
223	bcm2835_wdt_stop(&bcm2835_wdt_wdd);
224}
225
226static const struct of_device_id bcm2835_wdt_of_match[] = {
227	{ .compatible = "brcm,bcm2835-pm-wdt", },
228	{},
229};
230MODULE_DEVICE_TABLE(of, bcm2835_wdt_of_match);
231
232static struct platform_driver bcm2835_wdt_driver = {
233	.probe		= bcm2835_wdt_probe,
234	.remove		= bcm2835_wdt_remove,
235	.shutdown	= bcm2835_wdt_shutdown,
236	.driver = {
237		.name =		"bcm2835-wdt",
238		.of_match_table = bcm2835_wdt_of_match,
239	},
240};
241module_platform_driver(bcm2835_wdt_driver);
242
243module_param(heartbeat, uint, 0);
244MODULE_PARM_DESC(heartbeat, "Initial watchdog heartbeat in seconds");
245
246module_param(nowayout, bool, 0);
247MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
248				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
249
250MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
251MODULE_DESCRIPTION("Driver for Broadcom BCM2835 watchdog timer");
252MODULE_LICENSE("GPL");