1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Watchdog driver for Renesas WDT watchdog
4  *
5  * Copyright (C) 2015-17 Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
6  * Copyright (C) 2015-17 Renesas Electronics Corporation
7  */
8 #include <linux/bitops.h>
9 #include <linux/clk.h>
10 #include <linux/delay.h>
11 #include <linux/io.h>
12 #include <linux/iopoll.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/of.h>
16 #include <linux/platform_device.h>
17 #include <linux/pm_runtime.h>
18 #include <linux/smp.h>
19 #include <linux/sys_soc.h>
20 #include <linux/watchdog.h>
21 
22 #define RWTCNT		0
23 #define RWTCSRA		4
24 #define RWTCSRA_WOVF	BIT(4)
25 #define RWTCSRA_WRFLG	BIT(5)
26 #define RWTCSRA_TME	BIT(7)
27 #define RWTCSRB		8
28 
29 #define RWDT_DEFAULT_TIMEOUT 60U
30 
31 /*
32  * In probe, clk_rate is checked to be not more than 16 bit * biggest clock
33  * divider (12 bits). d is only a factor to fully utilize the WDT counter and
34  * will not exceed its 16 bits. Thus, no overflow, we stay below 32 bits.
35  */
36 #define MUL_BY_CLKS_PER_SEC(p, d) \
37 	DIV_ROUND_UP((d) * (p)->clk_rate, clk_divs[(p)->cks])
38 
39 /* d is 16 bit, clk_divs 12 bit -> no 32 bit overflow */
40 #define DIV_BY_CLKS_PER_SEC(p, d) ((d) * clk_divs[(p)->cks] / (p)->clk_rate)
41 
42 static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024, 4096 };
43 
44 static bool nowayout = WATCHDOG_NOWAYOUT;
45 module_param(nowayout, bool, 0);
46 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
47 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
48 
49 struct rwdt_priv {
50 	void __iomem *base;
51 	struct watchdog_device wdev;
52 	unsigned long clk_rate;
53 	u8 cks;
54 	struct clk *clk;
55 };
56 
57 static void rwdt_write(struct rwdt_priv *priv, u32 val, unsigned int reg)
58 {
59 	if (reg == RWTCNT)
60 		val |= 0x5a5a0000;
61 	else
62 		val |= 0xa5a5a500;
63 
64 	writel_relaxed(val, priv->base + reg);
65 }
66 
67 static int rwdt_init_timeout(struct watchdog_device *wdev)
68 {
69 	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
70 
71 	rwdt_write(priv, 65536 - MUL_BY_CLKS_PER_SEC(priv, wdev->timeout), RWTCNT);
72 
73 	return 0;
74 }
75 
76 static void rwdt_wait_cycles(struct rwdt_priv *priv, unsigned int cycles)
77 {
78 	unsigned int delay;
79 
80 	delay = DIV_ROUND_UP(cycles * 1000000, priv->clk_rate);
81 
82 	usleep_range(delay, 2 * delay);
83 }
84 
85 static int rwdt_start(struct watchdog_device *wdev)
86 {
87 	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
88 	u8 val;
89 
90 	pm_runtime_get_sync(wdev->parent);
91 
92 	/* Stop the timer before we modify any register */
93 	val = readb_relaxed(priv->base + RWTCSRA) & ~RWTCSRA_TME;
94 	rwdt_write(priv, val, RWTCSRA);
95 	/* Delay 2 cycles before setting watchdog counter */
96 	rwdt_wait_cycles(priv, 2);
97 
98 	rwdt_init_timeout(wdev);
99 	rwdt_write(priv, priv->cks, RWTCSRA);
100 	rwdt_write(priv, 0, RWTCSRB);
101 
102 	while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)
103 		cpu_relax();
104 
105 	rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
106 
107 	return 0;
108 }
109 
110 static int rwdt_stop(struct watchdog_device *wdev)
111 {
112 	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
113 
114 	rwdt_write(priv, priv->cks, RWTCSRA);
115 	/* Delay 3 cycles before disabling module clock */
116 	rwdt_wait_cycles(priv, 3);
117 	pm_runtime_put(wdev->parent);
118 
119 	return 0;
120 }
121 
122 static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev)
123 {
124 	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
125 	u16 val = readw_relaxed(priv->base + RWTCNT);
126 
127 	return DIV_BY_CLKS_PER_SEC(priv, 65536 - val);
128 }
129 
130 /* needs to be atomic - no RPM, no usleep_range, no scheduling! */
131 static int rwdt_restart(struct watchdog_device *wdev, unsigned long action,
132 			void *data)
133 {
134 	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
135 	u8 val;
136 
137 	clk_prepare_enable(priv->clk);
138 
139 	/* Stop the timer before we modify any register */
140 	val = readb_relaxed(priv->base + RWTCSRA) & ~RWTCSRA_TME;
141 	rwdt_write(priv, val, RWTCSRA);
142 	/* Delay 2 cycles before setting watchdog counter */
143 	udelay(DIV_ROUND_UP(2 * 1000000, priv->clk_rate));
144 
145 	rwdt_write(priv, 0xffff, RWTCNT);
146 	/* smallest divider to reboot soon */
147 	rwdt_write(priv, 0, RWTCSRA);
148 
149 	readb_poll_timeout_atomic(priv->base + RWTCSRA, val,
150 				  !(val & RWTCSRA_WRFLG), 1, 100);
151 
152 	rwdt_write(priv, RWTCSRA_TME, RWTCSRA);
153 
154 	/* wait 2 cycles, so watchdog will trigger */
155 	udelay(DIV_ROUND_UP(2 * 1000000, priv->clk_rate));
156 
157 	return 0;
158 }
159 
160 static const struct watchdog_info rwdt_ident = {
161 	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
162 		WDIOF_CARDRESET,
163 	.identity = "Renesas WDT Watchdog",
164 };
165 
166 static const struct watchdog_ops rwdt_ops = {
167 	.owner = THIS_MODULE,
168 	.start = rwdt_start,
169 	.stop = rwdt_stop,
170 	.ping = rwdt_init_timeout,
171 	.get_timeleft = rwdt_get_timeleft,
172 	.restart = rwdt_restart,
173 };
174 
175 #if defined(CONFIG_ARCH_RCAR_GEN2) && defined(CONFIG_SMP)
176 /*
177  * Watchdog-reset integration is broken on early revisions of R-Car Gen2 SoCs
178  */
179 static const struct soc_device_attribute rwdt_quirks_match[] = {
180 	{
181 		.soc_id = "r8a7790",
182 		.revision = "ES1.*",
183 		.data = (void *)1,	/* needs single CPU */
184 	}, {
185 		.soc_id = "r8a7791",
186 		.revision = "ES1.*",
187 		.data = (void *)1,	/* needs single CPU */
188 	}, {
189 		.soc_id = "r8a7792",
190 		.data = (void *)0,	/* needs SMP disabled */
191 	},
192 	{ /* sentinel */ }
193 };
194 
195 static bool rwdt_blacklisted(struct device *dev)
196 {
197 	const struct soc_device_attribute *attr;
198 
199 	attr = soc_device_match(rwdt_quirks_match);
200 	if (attr && setup_max_cpus > (uintptr_t)attr->data) {
201 		dev_info(dev, "Watchdog blacklisted on %s %s\n", attr->soc_id,
202 			 attr->revision);
203 		return true;
204 	}
205 
206 	return false;
207 }
208 #else /* !CONFIG_ARCH_RCAR_GEN2 || !CONFIG_SMP */
209 static inline bool rwdt_blacklisted(struct device *dev) { return false; }
210 #endif /* !CONFIG_ARCH_RCAR_GEN2 || !CONFIG_SMP */
211 
212 static int rwdt_probe(struct platform_device *pdev)
213 {
214 	struct device *dev = &pdev->dev;
215 	struct rwdt_priv *priv;
216 	unsigned long clks_per_sec;
217 	int ret, i;
218 	u8 csra;
219 
220 	if (rwdt_blacklisted(dev))
221 		return -ENODEV;
222 
223 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
224 	if (!priv)
225 		return -ENOMEM;
226 
227 	priv->base = devm_platform_ioremap_resource(pdev, 0);
228 	if (IS_ERR(priv->base))
229 		return PTR_ERR(priv->base);
230 
231 	priv->clk = devm_clk_get(dev, NULL);
232 	if (IS_ERR(priv->clk))
233 		return PTR_ERR(priv->clk);
234 
235 	pm_runtime_enable(dev);
236 	pm_runtime_get_sync(dev);
237 	priv->clk_rate = clk_get_rate(priv->clk);
238 	csra = readb_relaxed(priv->base + RWTCSRA);
239 	priv->wdev.bootstatus = csra & RWTCSRA_WOVF ? WDIOF_CARDRESET : 0;
240 	pm_runtime_put(dev);
241 
242 	if (!priv->clk_rate) {
243 		ret = -ENOENT;
244 		goto out_pm_disable;
245 	}
246 
247 	for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {
248 		clks_per_sec = priv->clk_rate / clk_divs[i];
249 		if (clks_per_sec && clks_per_sec < 65536) {
250 			priv->cks = i;
251 			break;
252 		}
253 	}
254 
255 	if (i < 0) {
256 		dev_err(dev, "Can't find suitable clock divider\n");
257 		ret = -ERANGE;
258 		goto out_pm_disable;
259 	}
260 
261 	priv->wdev.info = &rwdt_ident;
262 	priv->wdev.ops = &rwdt_ops;
263 	priv->wdev.parent = dev;
264 	priv->wdev.min_timeout = 1;
265 	priv->wdev.max_timeout = DIV_BY_CLKS_PER_SEC(priv, 65536);
266 	priv->wdev.timeout = min(priv->wdev.max_timeout, RWDT_DEFAULT_TIMEOUT);
267 
268 	platform_set_drvdata(pdev, priv);
269 	watchdog_set_drvdata(&priv->wdev, priv);
270 	watchdog_set_nowayout(&priv->wdev, nowayout);
271 	watchdog_set_restart_priority(&priv->wdev, 0);
272 	watchdog_stop_on_unregister(&priv->wdev);
273 
274 	/* This overrides the default timeout only if DT configuration was found */
275 	watchdog_init_timeout(&priv->wdev, 0, dev);
276 
277 	/* Check if FW enabled the watchdog */
278 	if (csra & RWTCSRA_TME) {
279 		/* Ensure properly initialized dividers */
280 		rwdt_start(&priv->wdev);
281 		set_bit(WDOG_HW_RUNNING, &priv->wdev.status);
282 	}
283 
284 	ret = watchdog_register_device(&priv->wdev);
285 	if (ret < 0)
286 		goto out_pm_disable;
287 
288 	return 0;
289 
290  out_pm_disable:
291 	pm_runtime_disable(dev);
292 	return ret;
293 }
294 
295 static void rwdt_remove(struct platform_device *pdev)
296 {
297 	struct rwdt_priv *priv = platform_get_drvdata(pdev);
298 
299 	watchdog_unregister_device(&priv->wdev);
300 	pm_runtime_disable(&pdev->dev);
301 }
302 
303 static int __maybe_unused rwdt_suspend(struct device *dev)
304 {
305 	struct rwdt_priv *priv = dev_get_drvdata(dev);
306 
307 	if (watchdog_active(&priv->wdev))
308 		rwdt_stop(&priv->wdev);
309 
310 	return 0;
311 }
312 
313 static int __maybe_unused rwdt_resume(struct device *dev)
314 {
315 	struct rwdt_priv *priv = dev_get_drvdata(dev);
316 
317 	if (watchdog_active(&priv->wdev))
318 		rwdt_start(&priv->wdev);
319 
320 	return 0;
321 }
322 
323 static SIMPLE_DEV_PM_OPS(rwdt_pm_ops, rwdt_suspend, rwdt_resume);
324 
325 static const struct of_device_id rwdt_ids[] = {
326 	{ .compatible = "renesas,rcar-gen2-wdt", },
327 	{ .compatible = "renesas,rcar-gen3-wdt", },
328 	{ .compatible = "renesas,rcar-gen4-wdt", },
329 	{ /* sentinel */ }
330 };
331 MODULE_DEVICE_TABLE(of, rwdt_ids);
332 
333 static struct platform_driver rwdt_driver = {
334 	.driver = {
335 		.name = "renesas_wdt",
336 		.of_match_table = rwdt_ids,
337 		.pm = &rwdt_pm_ops,
338 	},
339 	.probe = rwdt_probe,
340 	.remove_new = rwdt_remove,
341 };
342 module_platform_driver(rwdt_driver);
343 
344 MODULE_DESCRIPTION("Renesas WDT Watchdog Driver");
345 MODULE_LICENSE("GPL v2");
346 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
347