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
56 struct apple_wdt {
57 struct watchdog_device wdd;
58 void __iomem *regs;
59 unsigned long clk_rate;
60 };
61
to_apple_wdt(struct watchdog_device * wdd)62 static struct apple_wdt *to_apple_wdt(struct watchdog_device *wdd)
63 {
64 return container_of(wdd, struct apple_wdt, wdd);
65 }
66
apple_wdt_start(struct watchdog_device * wdd)67 static 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
apple_wdt_stop(struct watchdog_device * wdd)77 static 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
apple_wdt_ping(struct watchdog_device * wdd)86 static 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
apple_wdt_set_timeout(struct watchdog_device * wdd,unsigned int s)95 static int apple_wdt_set_timeout(struct watchdog_device *wdd, unsigned int s)
96 {
97 struct apple_wdt *wdt = to_apple_wdt(wdd);
98
99 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
100 writel_relaxed(wdt->clk_rate * s, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
101
102 wdd->timeout = s;
103
104 return 0;
105 }
106
apple_wdt_get_timeleft(struct watchdog_device * wdd)107 static unsigned int apple_wdt_get_timeleft(struct watchdog_device *wdd)
108 {
109 struct apple_wdt *wdt = to_apple_wdt(wdd);
110 u32 cur_time, reset_time;
111
112 cur_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
113 reset_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_BITE_TIME);
114
115 return (reset_time - cur_time) / wdt->clk_rate;
116 }
117
apple_wdt_restart(struct watchdog_device * wdd,unsigned long mode,void * cmd)118 static int apple_wdt_restart(struct watchdog_device *wdd, unsigned long mode,
119 void *cmd)
120 {
121 struct apple_wdt *wdt = to_apple_wdt(wdd);
122
123 writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL);
124 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_BITE_TIME);
125 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME);
126
127 /*
128 * Flush writes and then wait for the SoC to reset. Even though the
129 * reset is queued almost immediately experiments have shown that it
130 * can take up to ~20-25ms until the SoC is actually reset. Just wait
131 * 50ms here to be safe.
132 */
133 (void)readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME);
134 mdelay(50);
135
136 return 0;
137 }
138
139 static struct watchdog_ops apple_wdt_ops = {
140 .owner = THIS_MODULE,
141 .start = apple_wdt_start,
142 .stop = apple_wdt_stop,
143 .ping = apple_wdt_ping,
144 .set_timeout = apple_wdt_set_timeout,
145 .get_timeleft = apple_wdt_get_timeleft,
146 .restart = apple_wdt_restart,
147 };
148
149 static struct watchdog_info apple_wdt_info = {
150 .identity = "Apple SoC Watchdog",
151 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
152 };
153
apple_wdt_probe(struct platform_device * pdev)154 static int apple_wdt_probe(struct platform_device *pdev)
155 {
156 struct device *dev = &pdev->dev;
157 struct apple_wdt *wdt;
158 struct clk *clk;
159 u32 wdt_ctrl;
160
161 wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
162 if (!wdt)
163 return -ENOMEM;
164
165 wdt->regs = devm_platform_ioremap_resource(pdev, 0);
166 if (IS_ERR(wdt->regs))
167 return PTR_ERR(wdt->regs);
168
169 clk = devm_clk_get_enabled(dev, NULL);
170 if (IS_ERR(clk))
171 return PTR_ERR(clk);
172 wdt->clk_rate = clk_get_rate(clk);
173 if (!wdt->clk_rate)
174 return -EINVAL;
175
176 wdt->wdd.ops = &apple_wdt_ops;
177 wdt->wdd.info = &apple_wdt_info;
178 wdt->wdd.max_timeout = U32_MAX / wdt->clk_rate;
179 wdt->wdd.timeout = APPLE_WDT_TIMEOUT_DEFAULT;
180
181 wdt_ctrl = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CTRL);
182 if (wdt_ctrl & APPLE_WDT_CTRL_RESET_EN)
183 set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
184
185 watchdog_init_timeout(&wdt->wdd, 0, dev);
186 apple_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout);
187 watchdog_stop_on_unregister(&wdt->wdd);
188 watchdog_set_restart_priority(&wdt->wdd, 128);
189
190 return devm_watchdog_register_device(dev, &wdt->wdd);
191 }
192
193 static const struct of_device_id apple_wdt_of_match[] = {
194 { .compatible = "apple,wdt" },
195 {},
196 };
197 MODULE_DEVICE_TABLE(of, apple_wdt_of_match);
198
199 static struct platform_driver apple_wdt_driver = {
200 .driver = {
201 .name = "apple-watchdog",
202 .of_match_table = apple_wdt_of_match,
203 },
204 .probe = apple_wdt_probe,
205 };
206 module_platform_driver(apple_wdt_driver);
207
208 MODULE_DESCRIPTION("Apple SoC watchdog driver");
209 MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
210 MODULE_LICENSE("Dual MIT/GPL");
211