apple_wdt.c

  1// SPDX-License-Identifier: GPL-2.0-only OR MIT
  2/*
  3 * Apple SoC Watchdog driver
  4 *
  5 * Copyright (C) The Asahi Linux Contributors
  6 */
  7
  8#include <linux/bits.h>
  9#include <linux/clk.h>
 10#include <linux/delay.h>
 11#include <linux/io.h>
 12#include <linux/kernel.h>
 13#include <linux/limits.h>
 14#include <linux/module.h>
 15#include <linux/of.h>
 16#include <linux/platform_device.h>
 17#include <linux/watchdog.h>
 18
 19/*
 20 * Apple Watchdog MMIO registers
 21 *
 22 * This HW block has three separate watchdogs. WD0 resets the machine
 23 * to recovery mode and is not very useful for us. WD1 and WD2 trigger a normal
 24 * machine reset. WD0 additionally supports a configurable interrupt.
 25 * This information can be used to implement pretimeout support at a later time.
 26 *
 27 * APPLE_WDT_WDx_CUR_TIME is a simple counter incremented for each tick of the
 28 * reference clock. It can also be overwritten to any value.
 29 * Whenever APPLE_WDT_CTRL_RESET_EN is set in APPLE_WDT_WDx_CTRL and
 30 * APPLE_WDT_WDx_CUR_TIME >= APPLE_WDT_WDx_BITE_TIME the entire machine is
 31 * reset.
 32 * Whenever APPLE_WDT_CTRL_IRQ_EN is set and APPLE_WDTx_WD1_CUR_TIME >=
 33 * APPLE_WDTx_WD1_BARK_TIME an interrupt is triggered and
 34 * APPLE_WDT_CTRL_IRQ_STATUS is set. The interrupt can be cleared by writing
 35 * 1 to APPLE_WDT_CTRL_IRQ_STATUS.
 36 */
 37#define APPLE_WDT_WD0_CUR_TIME		0x00
 38#define APPLE_WDT_WD0_BITE_TIME		0x04
 39#define APPLE_WDT_WD0_BARK_TIME		0x08
 40#define APPLE_WDT_WD0_CTRL		0x0c
 41
 42#define APPLE_WDT_WD1_CUR_TIME		0x10
 43#define APPLE_WDT_WD1_BITE_TIME		0x14
 44#define APPLE_WDT_WD1_CTRL		0x1c
 45
 46#define APPLE_WDT_WD2_CUR_TIME		0x20
 47#define APPLE_WDT_WD2_BITE_TIME		0x24
 48#define APPLE_WDT_WD2_CTRL		0x2c
 49
 50#define APPLE_WDT_CTRL_IRQ_EN		BIT(0)
 51#define APPLE_WDT_CTRL_IRQ_STATUS	BIT(1)
 52#define APPLE_WDT_CTRL_RESET_EN		BIT(2)
 53
 54#define APPLE_WDT_TIMEOUT_DEFAULT	30
 55
 56struct apple_wdt {
 57	struct watchdog_device wdd;
 58	void __iomem *regs;
 59	unsigned long clk_rate;
 60};
 61
 62static struct apple_wdt *to_apple_wdt(struct watchdog_device *wdd)
 63{
 64	return container_of(wdd, struct apple_wdt, wdd);
 65}
 66
 67static int apple_wdt_start(struct watchdog_device *wdd)
 68{
 69	struct apple_wdt *wdt = to_apple_wdt(wdd);
 70
 71	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
 72	writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL);
 73
 74	return 0;
 75}
 76
 77static int apple_wdt_stop(struct watchdog_device *wdd)
 78{
 79	struct apple_wdt *wdt = to_apple_wdt(wdd);
 80
 81	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CTRL);
 82
 83	return 0;
 84}
 85
 86static int apple_wdt_ping(struct watchdog_device *wdd)
 87{
 88	struct apple_wdt *wdt = to_apple_wdt(wdd);
 89
 90	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
 91
 92	return 0;
 93}
 94
 95static int apple_wdt_set_timeout(struct watchdog_device *wdd, unsigned int s)
 96{
 97	struct apple_wdt *wdt = to_apple_wdt(wdd);
 98	u32 actual;
 99
100	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
101
102	actual = min(s, wdd->max_hw_heartbeat_ms / 1000);
103	writel_relaxed(wdt->clk_rate * actual, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
104
105	wdd->timeout = s;
106
107	return 0;
108}
109
110static unsigned int apple_wdt_get_timeleft(struct watchdog_device *wdd)
111{
112	struct apple_wdt *wdt = to_apple_wdt(wdd);
113	u32 cur_time, reset_time;
114
115	cur_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
116	reset_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_BITE_TIME);
117
118	return (reset_time - cur_time) / wdt->clk_rate;
119}
120
121static int apple_wdt_restart(struct watchdog_device *wdd, unsigned long mode,
122			     void *cmd)
123{
124	struct apple_wdt *wdt = to_apple_wdt(wdd);
125
126	writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL);
127	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
128	writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
129
130	/*
131	 * Flush writes and then wait for the SoC to reset. Even though the
132	 * reset is queued almost immediately experiments have shown that it
133	 * can take up to ~120-125ms until the SoC is actually reset. Just
134	 * wait 150ms here to be safe.
135	 */
136	(void)readl(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
137	mdelay(150);
138
139	return 0;
140}
141
142static struct watchdog_ops apple_wdt_ops = {
143	.owner = THIS_MODULE,
144	.start = apple_wdt_start,
145	.stop = apple_wdt_stop,
146	.ping = apple_wdt_ping,
147	.set_timeout = apple_wdt_set_timeout,
148	.get_timeleft = apple_wdt_get_timeleft,
149	.restart = apple_wdt_restart,
150};
151
152static struct watchdog_info apple_wdt_info = {
153	.identity = "Apple SoC Watchdog",
154	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
155};
156
157static int apple_wdt_probe(struct platform_device *pdev)
158{
159	struct device *dev = &pdev->dev;
160	struct apple_wdt *wdt;
161	struct clk *clk;
162	u32 wdt_ctrl;
163
164	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
165	if (!wdt)
166		return -ENOMEM;
167
168	wdt->regs = devm_platform_ioremap_resource(pdev, 0);
169	if (IS_ERR(wdt->regs))
170		return PTR_ERR(wdt->regs);
171
172	clk = devm_clk_get_enabled(dev, NULL);
173	if (IS_ERR(clk))
174		return PTR_ERR(clk);
175	wdt->clk_rate = clk_get_rate(clk);
176	if (!wdt->clk_rate)
177		return -EINVAL;
178
179	platform_set_drvdata(pdev, wdt);
180
181	wdt->wdd.ops = &apple_wdt_ops;
182	wdt->wdd.info = &apple_wdt_info;
183	wdt->wdd.max_hw_heartbeat_ms = U32_MAX / wdt->clk_rate * 1000;
184	wdt->wdd.timeout = APPLE_WDT_TIMEOUT_DEFAULT;
185
186	wdt_ctrl = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CTRL);
187	if (wdt_ctrl & APPLE_WDT_CTRL_RESET_EN)
188		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
189
190	watchdog_init_timeout(&wdt->wdd, 0, dev);
191	apple_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout);
192	watchdog_stop_on_unregister(&wdt->wdd);
193	watchdog_set_restart_priority(&wdt->wdd, 128);
194
195	return devm_watchdog_register_device(dev, &wdt->wdd);
196}
197
198static int apple_wdt_resume(struct device *dev)
199{
200	struct apple_wdt *wdt = dev_get_drvdata(dev);
201
202	if (watchdog_active(&wdt->wdd) || watchdog_hw_running(&wdt->wdd))
203		apple_wdt_start(&wdt->wdd);
204
205	return 0;
206}
207
208static int apple_wdt_suspend(struct device *dev)
209{
210	struct apple_wdt *wdt = dev_get_drvdata(dev);
211
212	if (watchdog_active(&wdt->wdd) || watchdog_hw_running(&wdt->wdd))
213		apple_wdt_stop(&wdt->wdd);
214
215	return 0;
216}
217
218static DEFINE_SIMPLE_DEV_PM_OPS(apple_wdt_pm_ops, apple_wdt_suspend, apple_wdt_resume);
219
220static const struct of_device_id apple_wdt_of_match[] = {
221	{ .compatible = "apple,wdt" },
222	{},
223};
224MODULE_DEVICE_TABLE(of, apple_wdt_of_match);
225
226static struct platform_driver apple_wdt_driver = {
227	.driver = {
228		.name = "apple-watchdog",
229		.of_match_table = apple_wdt_of_match,
230		.pm = pm_sleep_ptr(&apple_wdt_pm_ops),
231	},
232	.probe = apple_wdt_probe,
233};
234module_platform_driver(apple_wdt_driver);
235
236MODULE_DESCRIPTION("Apple SoC watchdog driver");
237MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
238MODULE_LICENSE("Dual MIT/GPL");