1 // SPDX-License-Identifier: GPL-2.0-only
2 
3 /*
4  * Realtek Otto MIPS platform watchdog
5  *
6  * Watchdog timer that will reset the system after timeout, using the selected
7  * reset mode.
8  *
9  * Counter scaling and timeouts:
10  * - Base prescale of (2 << 25), providing tick duration T_0: 168ms @ 200MHz
11  * - PRESCALE: logarithmic prescaler adding a factor of {1, 2, 4, 8}
12  * - Phase 1: Times out after (PHASE1 + 1) × PRESCALE × T_0
13  *   Generates an interrupt, WDT cannot be stopped after phase 1
14  * - Phase 2: starts after phase 1, times out after (PHASE2 + 1) × PRESCALE × T_0
15  *   Resets the system according to RST_MODE
16  */
17 
18 #include <linux/bits.h>
19 #include <linux/bitfield.h>
20 #include <linux/clk.h>
21 #include <linux/delay.h>
22 #include <linux/interrupt.h>
23 #include <linux/io.h>
24 #include <linux/math.h>
25 #include <linux/minmax.h>
26 #include <linux/module.h>
27 #include <linux/mod_devicetable.h>
28 #include <linux/platform_device.h>
29 #include <linux/property.h>
30 #include <linux/reboot.h>
31 #include <linux/watchdog.h>
32 
33 #define OTTO_WDT_REG_CNTR		0x0
34 #define OTTO_WDT_CNTR_PING		BIT(31)
35 
36 #define OTTO_WDT_REG_INTR		0x4
37 #define OTTO_WDT_INTR_PHASE_1		BIT(31)
38 #define OTTO_WDT_INTR_PHASE_2		BIT(30)
39 
40 #define OTTO_WDT_REG_CTRL		0x8
41 #define OTTO_WDT_CTRL_ENABLE		BIT(31)
42 #define OTTO_WDT_CTRL_PRESCALE		GENMASK(30, 29)
43 #define OTTO_WDT_CTRL_PHASE1		GENMASK(26, 22)
44 #define OTTO_WDT_CTRL_PHASE2		GENMASK(19, 15)
45 #define OTTO_WDT_CTRL_RST_MODE		GENMASK(1, 0)
46 #define OTTO_WDT_MODE_SOC		0
47 #define OTTO_WDT_MODE_CPU		1
48 #define OTTO_WDT_MODE_SOFTWARE		2
49 #define OTTO_WDT_CTRL_DEFAULT		OTTO_WDT_MODE_CPU
50 
51 #define OTTO_WDT_PRESCALE_MAX		3
52 
53 /*
54  * One higher than the max values contained in PHASE{1,2}, since a value of 0
55  * corresponds to one tick.
56  */
57 #define OTTO_WDT_PHASE_TICKS_MAX	32
58 
59 /*
60  * The maximum reset delay is actually 2×32 ticks, but that would require large
61  * pretimeout values for timeouts longer than 32 ticks. Limit the maximum timeout
62  * to 32 + 1 to ensure small pretimeout values can be configured as expected.
63  */
64 #define OTTO_WDT_TIMEOUT_TICKS_MAX	(OTTO_WDT_PHASE_TICKS_MAX + 1)
65 
66 struct otto_wdt_ctrl {
67 	struct watchdog_device wdev;
68 	struct device *dev;
69 	void __iomem *base;
70 	unsigned int clk_rate_khz;
71 	int irq_phase1;
72 };
73 
74 static int otto_wdt_start(struct watchdog_device *wdev)
75 {
76 	struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
77 	u32 v;
78 
79 	v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
80 	v |= OTTO_WDT_CTRL_ENABLE;
81 	iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
82 
83 	return 0;
84 }
85 
86 static int otto_wdt_stop(struct watchdog_device *wdev)
87 {
88 	struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
89 	u32 v;
90 
91 	v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
92 	v &= ~OTTO_WDT_CTRL_ENABLE;
93 	iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
94 
95 	return 0;
96 }
97 
98 static int otto_wdt_ping(struct watchdog_device *wdev)
99 {
100 	struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
101 
102 	iowrite32(OTTO_WDT_CNTR_PING, ctrl->base + OTTO_WDT_REG_CNTR);
103 
104 	return 0;
105 }
106 
107 static int otto_wdt_tick_ms(struct otto_wdt_ctrl *ctrl, int prescale)
108 {
109 	return DIV_ROUND_CLOSEST(1 << (25 + prescale), ctrl->clk_rate_khz);
110 }
111 
112 /*
113  * The timer asserts the PHASE1/PHASE2 IRQs when the number of ticks exceeds
114  * the value stored in those fields. This means each phase will run for at least
115  * one tick, so small values need to be clamped to correctly reflect the timeout.
116  */
117 static inline unsigned int div_round_ticks(unsigned int val, unsigned int tick_duration,
118 		unsigned int min_ticks)
119 {
120 	return max(min_ticks, DIV_ROUND_UP(val, tick_duration));
121 }
122 
123 static int otto_wdt_determine_timeouts(struct watchdog_device *wdev, unsigned int timeout,
124 		unsigned int pretimeout)
125 {
126 	struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
127 	unsigned int pretimeout_ms = pretimeout * 1000;
128 	unsigned int timeout_ms = timeout * 1000;
129 	unsigned int prescale_next = 0;
130 	unsigned int phase1_ticks;
131 	unsigned int phase2_ticks;
132 	unsigned int total_ticks;
133 	unsigned int prescale;
134 	unsigned int tick_ms;
135 	u32 v;
136 
137 	do {
138 		prescale = prescale_next;
139 		if (prescale > OTTO_WDT_PRESCALE_MAX)
140 			return -EINVAL;
141 
142 		tick_ms = otto_wdt_tick_ms(ctrl, prescale);
143 		total_ticks = div_round_ticks(timeout_ms, tick_ms, 2);
144 		phase1_ticks = div_round_ticks(timeout_ms - pretimeout_ms, tick_ms, 1);
145 		phase2_ticks = total_ticks - phase1_ticks;
146 
147 		prescale_next++;
148 	} while (phase1_ticks > OTTO_WDT_PHASE_TICKS_MAX
149 		|| phase2_ticks > OTTO_WDT_PHASE_TICKS_MAX);
150 
151 	v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
152 
153 	v &= ~(OTTO_WDT_CTRL_PRESCALE | OTTO_WDT_CTRL_PHASE1 | OTTO_WDT_CTRL_PHASE2);
154 	v |= FIELD_PREP(OTTO_WDT_CTRL_PHASE1, phase1_ticks - 1);
155 	v |= FIELD_PREP(OTTO_WDT_CTRL_PHASE2, phase2_ticks - 1);
156 	v |= FIELD_PREP(OTTO_WDT_CTRL_PRESCALE, prescale);
157 
158 	iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
159 
160 	timeout_ms = total_ticks * tick_ms;
161 	ctrl->wdev.timeout = timeout_ms / 1000;
162 
163 	pretimeout_ms = phase2_ticks * tick_ms;
164 	ctrl->wdev.pretimeout = pretimeout_ms / 1000;
165 
166 	return 0;
167 }
168 
169 static int otto_wdt_set_timeout(struct watchdog_device *wdev, unsigned int val)
170 {
171 	return otto_wdt_determine_timeouts(wdev, val, min(wdev->pretimeout, val - 1));
172 }
173 
174 static int otto_wdt_set_pretimeout(struct watchdog_device *wdev, unsigned int val)
175 {
176 	return otto_wdt_determine_timeouts(wdev, wdev->timeout, val);
177 }
178 
179 static int otto_wdt_restart(struct watchdog_device *wdev, unsigned long reboot_mode,
180 		void *data)
181 {
182 	struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
183 	u32 reset_mode;
184 	u32 v;
185 
186 	disable_irq(ctrl->irq_phase1);
187 
188 	switch (reboot_mode) {
189 	case REBOOT_SOFT:
190 		reset_mode = OTTO_WDT_MODE_SOFTWARE;
191 		break;
192 	case REBOOT_WARM:
193 		reset_mode = OTTO_WDT_MODE_CPU;
194 		break;
195 	default:
196 		reset_mode = OTTO_WDT_MODE_SOC;
197 		break;
198 	}
199 
200 	/* Configure for shortest timeout and wait for reset to occur */
201 	v = FIELD_PREP(OTTO_WDT_CTRL_RST_MODE, reset_mode) | OTTO_WDT_CTRL_ENABLE;
202 	iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
203 
204 	mdelay(3 * otto_wdt_tick_ms(ctrl, 0));
205 
206 	return 0;
207 }
208 
209 static irqreturn_t otto_wdt_phase1_isr(int irq, void *dev_id)
210 {
211 	struct otto_wdt_ctrl *ctrl = dev_id;
212 
213 	iowrite32(OTTO_WDT_INTR_PHASE_1, ctrl->base + OTTO_WDT_REG_INTR);
214 	dev_crit(ctrl->dev, "phase 1 timeout\n");
215 	watchdog_notify_pretimeout(&ctrl->wdev);
216 
217 	return IRQ_HANDLED;
218 }
219 
220 static const struct watchdog_ops otto_wdt_ops = {
221 	.owner = THIS_MODULE,
222 	.start = otto_wdt_start,
223 	.stop = otto_wdt_stop,
224 	.ping = otto_wdt_ping,
225 	.set_timeout = otto_wdt_set_timeout,
226 	.set_pretimeout = otto_wdt_set_pretimeout,
227 	.restart = otto_wdt_restart,
228 };
229 
230 static const struct watchdog_info otto_wdt_info = {
231 	.identity = "Realtek Otto watchdog timer",
232 	.options = WDIOF_KEEPALIVEPING |
233 		WDIOF_MAGICCLOSE |
234 		WDIOF_SETTIMEOUT |
235 		WDIOF_PRETIMEOUT,
236 };
237 
238 static void otto_wdt_clock_action(void *data)
239 {
240 	clk_disable_unprepare(data);
241 }
242 
243 static int otto_wdt_probe_clk(struct otto_wdt_ctrl *ctrl)
244 {
245 	struct clk *clk = devm_clk_get(ctrl->dev, NULL);
246 	int ret;
247 
248 	if (IS_ERR(clk))
249 		return dev_err_probe(ctrl->dev, PTR_ERR(clk), "Failed to get clock\n");
250 
251 	ret = clk_prepare_enable(clk);
252 	if (ret)
253 		return dev_err_probe(ctrl->dev, ret, "Failed to enable clock\n");
254 
255 	ret = devm_add_action_or_reset(ctrl->dev, otto_wdt_clock_action, clk);
256 	if (ret)
257 		return ret;
258 
259 	ctrl->clk_rate_khz = clk_get_rate(clk) / 1000;
260 	if (ctrl->clk_rate_khz == 0)
261 		return dev_err_probe(ctrl->dev, -ENXIO, "Failed to get clock rate\n");
262 
263 	return 0;
264 }
265 
266 static int otto_wdt_probe_reset_mode(struct otto_wdt_ctrl *ctrl)
267 {
268 	static const char *mode_property = "realtek,reset-mode";
269 	const struct fwnode_handle *node = ctrl->dev->fwnode;
270 	int mode_count;
271 	u32 mode;
272 	u32 v;
273 
274 	if (!node)
275 		return -ENXIO;
276 
277 	mode_count = fwnode_property_string_array_count(node, mode_property);
278 	if (mode_count < 0)
279 		return mode_count;
280 	else if (mode_count == 0)
281 		return 0;
282 	else if (mode_count != 1)
283 		return -EINVAL;
284 
285 	if (fwnode_property_match_string(node, mode_property, "soc") == 0)
286 		mode = OTTO_WDT_MODE_SOC;
287 	else if (fwnode_property_match_string(node, mode_property, "cpu") == 0)
288 		mode = OTTO_WDT_MODE_CPU;
289 	else if (fwnode_property_match_string(node, mode_property, "software") == 0)
290 		mode = OTTO_WDT_MODE_SOFTWARE;
291 	else
292 		return -EINVAL;
293 
294 	v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
295 	v &= ~OTTO_WDT_CTRL_RST_MODE;
296 	v |= FIELD_PREP(OTTO_WDT_CTRL_RST_MODE, mode);
297 	iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
298 
299 	return 0;
300 }
301 
302 static int otto_wdt_probe(struct platform_device *pdev)
303 {
304 	struct device *dev = &pdev->dev;
305 	struct otto_wdt_ctrl *ctrl;
306 	unsigned int max_tick_ms;
307 	int ret;
308 
309 	ctrl = devm_kzalloc(dev, sizeof(*ctrl), GFP_KERNEL);
310 	if (!ctrl)
311 		return -ENOMEM;
312 
313 	ctrl->dev = dev;
314 	ctrl->base = devm_platform_ioremap_resource(pdev, 0);
315 	if (IS_ERR(ctrl->base))
316 		return PTR_ERR(ctrl->base);
317 
318 	/* Clear any old interrupts and reset initial state */
319 	iowrite32(OTTO_WDT_INTR_PHASE_1 | OTTO_WDT_INTR_PHASE_2,
320 			ctrl->base + OTTO_WDT_REG_INTR);
321 	iowrite32(OTTO_WDT_CTRL_DEFAULT, ctrl->base + OTTO_WDT_REG_CTRL);
322 
323 	ret = otto_wdt_probe_clk(ctrl);
324 	if (ret)
325 		return ret;
326 
327 	ctrl->irq_phase1 = platform_get_irq_byname(pdev, "phase1");
328 	if (ctrl->irq_phase1 < 0)
329 		return ctrl->irq_phase1;
330 
331 	ret = devm_request_irq(dev, ctrl->irq_phase1, otto_wdt_phase1_isr, 0,
332 			"realtek-otto-wdt", ctrl);
333 	if (ret)
334 		return dev_err_probe(dev, ret, "Failed to get IRQ for phase1\n");
335 
336 	ret = otto_wdt_probe_reset_mode(ctrl);
337 	if (ret)
338 		return dev_err_probe(dev, ret, "Invalid reset mode specified\n");
339 
340 	ctrl->wdev.parent = dev;
341 	ctrl->wdev.info = &otto_wdt_info;
342 	ctrl->wdev.ops = &otto_wdt_ops;
343 
344 	/*
345 	 * Since pretimeout cannot be disabled, min. timeout is twice the
346 	 * subsystem resolution. Max. timeout is ca. 43s at a bus clock of 200MHz.
347 	 */
348 	ctrl->wdev.min_timeout = 2;
349 	max_tick_ms = otto_wdt_tick_ms(ctrl, OTTO_WDT_PRESCALE_MAX);
350 	ctrl->wdev.max_hw_heartbeat_ms = max_tick_ms * OTTO_WDT_TIMEOUT_TICKS_MAX;
351 	ctrl->wdev.timeout = min(30U, ctrl->wdev.max_hw_heartbeat_ms / 1000);
352 
353 	watchdog_set_drvdata(&ctrl->wdev, ctrl);
354 	watchdog_init_timeout(&ctrl->wdev, 0, dev);
355 	watchdog_stop_on_reboot(&ctrl->wdev);
356 	watchdog_set_restart_priority(&ctrl->wdev, 128);
357 
358 	ret = otto_wdt_determine_timeouts(&ctrl->wdev, ctrl->wdev.timeout, 1);
359 	if (ret)
360 		return dev_err_probe(dev, ret, "Failed to set timeout\n");
361 
362 	return devm_watchdog_register_device(dev, &ctrl->wdev);
363 }
364 
365 static const struct of_device_id otto_wdt_ids[] = {
366 	{ .compatible = "realtek,rtl8380-wdt" },
367 	{ .compatible = "realtek,rtl8390-wdt" },
368 	{ .compatible = "realtek,rtl9300-wdt" },
369 	{ }
370 };
371 MODULE_DEVICE_TABLE(of, otto_wdt_ids);
372 
373 static struct platform_driver otto_wdt_driver = {
374 	.probe = otto_wdt_probe,
375 	.driver = {
376 		.name = "realtek-otto-watchdog",
377 		.of_match_table	= otto_wdt_ids,
378 	},
379 };
380 module_platform_driver(otto_wdt_driver);
381 
382 MODULE_LICENSE("GPL v2");
383 MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
384 MODULE_DESCRIPTION("Realtek Otto watchdog timer driver");
385