1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Renesas RZ/A Series WDT Driver
4 *
5 * Copyright (C) 2017 Renesas Electronics America, Inc.
6 * Copyright (C) 2017 Chris Brandt
7 */
8
9 #include <linux/bitops.h>
10 #include <linux/clk.h>
11 #include <linux/delay.h>
12 #include <linux/module.h>
13 #include <linux/of_address.h>
14 #include <linux/of_device.h>
15 #include <linux/platform_device.h>
16 #include <linux/watchdog.h>
17
18 #define DEFAULT_TIMEOUT 30
19
20 /* Watchdog Timer Registers */
21 #define WTCSR 0
22 #define WTCSR_MAGIC 0xA500
23 #define WTSCR_WT BIT(6)
24 #define WTSCR_TME BIT(5)
25 #define WTSCR_CKS(i) (i)
26
27 #define WTCNT 2
28 #define WTCNT_MAGIC 0x5A00
29
30 #define WRCSR 4
31 #define WRCSR_MAGIC 0x5A00
32 #define WRCSR_RSTE BIT(6)
33 #define WRCSR_CLEAR_WOVF 0xA500 /* special value */
34
35 /* The maximum CKS register setting value to get the longest timeout */
36 #define CKS_3BIT 0x7
37 #define CKS_4BIT 0xF
38
39 #define DIVIDER_3BIT 16384 /* Clock divider when CKS = 0x7 */
40 #define DIVIDER_4BIT 4194304 /* Clock divider when CKS = 0xF */
41
42 struct rza_wdt {
43 struct watchdog_device wdev;
44 void __iomem *base;
45 struct clk *clk;
46 u8 count;
47 u8 cks;
48 };
49
rza_wdt_calc_timeout(struct rza_wdt * priv,int timeout)50 static void rza_wdt_calc_timeout(struct rza_wdt *priv, int timeout)
51 {
52 unsigned long rate = clk_get_rate(priv->clk);
53 unsigned int ticks;
54
55 if (priv->cks == CKS_4BIT) {
56 ticks = DIV_ROUND_UP(timeout * rate, DIVIDER_4BIT);
57
58 /*
59 * Since max_timeout was set in probe, we know that the timeout
60 * value passed will never calculate to a tick value greater
61 * than 256.
62 */
63 priv->count = 256 - ticks;
64
65 } else {
66 /* Start timer with longest timeout */
67 priv->count = 0;
68 }
69
70 pr_debug("%s: timeout set to %u (WTCNT=%d)\n", __func__,
71 timeout, priv->count);
72 }
73
rza_wdt_start(struct watchdog_device * wdev)74 static int rza_wdt_start(struct watchdog_device *wdev)
75 {
76 struct rza_wdt *priv = watchdog_get_drvdata(wdev);
77
78 /* Stop timer */
79 writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
80
81 /* Must dummy read WRCSR:WOVF at least once before clearing */
82 readb(priv->base + WRCSR);
83 writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
84
85 rza_wdt_calc_timeout(priv, wdev->timeout);
86
87 writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
88 writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT);
89 writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME |
90 WTSCR_CKS(priv->cks), priv->base + WTCSR);
91
92 return 0;
93 }
94
rza_wdt_stop(struct watchdog_device * wdev)95 static int rza_wdt_stop(struct watchdog_device *wdev)
96 {
97 struct rza_wdt *priv = watchdog_get_drvdata(wdev);
98
99 writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
100
101 return 0;
102 }
103
rza_wdt_ping(struct watchdog_device * wdev)104 static int rza_wdt_ping(struct watchdog_device *wdev)
105 {
106 struct rza_wdt *priv = watchdog_get_drvdata(wdev);
107
108 writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT);
109
110 pr_debug("%s: timeout = %u\n", __func__, wdev->timeout);
111
112 return 0;
113 }
114
rza_set_timeout(struct watchdog_device * wdev,unsigned int timeout)115 static int rza_set_timeout(struct watchdog_device *wdev, unsigned int timeout)
116 {
117 wdev->timeout = timeout;
118 rza_wdt_start(wdev);
119 return 0;
120 }
121
rza_wdt_restart(struct watchdog_device * wdev,unsigned long action,void * data)122 static int rza_wdt_restart(struct watchdog_device *wdev, unsigned long action,
123 void *data)
124 {
125 struct rza_wdt *priv = watchdog_get_drvdata(wdev);
126
127 /* Stop timer */
128 writew(WTCSR_MAGIC | 0, priv->base + WTCSR);
129
130 /* Must dummy read WRCSR:WOVF at least once before clearing */
131 readb(priv->base + WRCSR);
132 writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR);
133
134 /*
135 * Start timer with fastest clock source and only 1 clock left before
136 * overflow with reset option enabled.
137 */
138 writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR);
139 writew(WTCNT_MAGIC | 255, priv->base + WTCNT);
140 writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, priv->base + WTCSR);
141
142 /*
143 * Actually make sure the above sequence hits hardware before sleeping.
144 */
145 wmb();
146
147 /* Wait for WDT overflow (reset) */
148 udelay(20);
149
150 return 0;
151 }
152
153 static const struct watchdog_info rza_wdt_ident = {
154 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
155 .identity = "Renesas RZ/A WDT Watchdog",
156 };
157
158 static const struct watchdog_ops rza_wdt_ops = {
159 .owner = THIS_MODULE,
160 .start = rza_wdt_start,
161 .stop = rza_wdt_stop,
162 .ping = rza_wdt_ping,
163 .set_timeout = rza_set_timeout,
164 .restart = rza_wdt_restart,
165 };
166
rza_wdt_probe(struct platform_device * pdev)167 static int rza_wdt_probe(struct platform_device *pdev)
168 {
169 struct device *dev = &pdev->dev;
170 struct rza_wdt *priv;
171 unsigned long rate;
172 int ret;
173
174 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
175 if (!priv)
176 return -ENOMEM;
177
178 priv->base = devm_platform_ioremap_resource(pdev, 0);
179 if (IS_ERR(priv->base))
180 return PTR_ERR(priv->base);
181
182 priv->clk = devm_clk_get(dev, NULL);
183 if (IS_ERR(priv->clk))
184 return PTR_ERR(priv->clk);
185
186 rate = clk_get_rate(priv->clk);
187 if (rate < 16384) {
188 dev_err(dev, "invalid clock rate (%ld)\n", rate);
189 return -ENOENT;
190 }
191
192 priv->wdev.info = &rza_wdt_ident;
193 priv->wdev.ops = &rza_wdt_ops;
194 priv->wdev.parent = dev;
195
196 priv->cks = (u8)(uintptr_t) of_device_get_match_data(dev);
197 if (priv->cks == CKS_4BIT) {
198 /* Assume slowest clock rate possible (CKS=0xF) */
199 priv->wdev.max_timeout = (DIVIDER_4BIT * U8_MAX) / rate;
200
201 } else if (priv->cks == CKS_3BIT) {
202 /* Assume slowest clock rate possible (CKS=7) */
203 rate /= DIVIDER_3BIT;
204
205 /*
206 * Since the max possible timeout of our 8-bit count
207 * register is less than a second, we must use
208 * max_hw_heartbeat_ms.
209 */
210 priv->wdev.max_hw_heartbeat_ms = (1000 * U8_MAX) / rate;
211 dev_dbg(dev, "max hw timeout of %dms\n",
212 priv->wdev.max_hw_heartbeat_ms);
213 }
214
215 priv->wdev.min_timeout = 1;
216 priv->wdev.timeout = DEFAULT_TIMEOUT;
217
218 watchdog_init_timeout(&priv->wdev, 0, dev);
219 watchdog_set_drvdata(&priv->wdev, priv);
220
221 ret = devm_watchdog_register_device(dev, &priv->wdev);
222 if (ret)
223 dev_err(dev, "Cannot register watchdog device\n");
224
225 return ret;
226 }
227
228 static const struct of_device_id rza_wdt_of_match[] = {
229 { .compatible = "renesas,r7s9210-wdt", .data = (void *)CKS_4BIT, },
230 { .compatible = "renesas,rza-wdt", .data = (void *)CKS_3BIT, },
231 { /* sentinel */ }
232 };
233 MODULE_DEVICE_TABLE(of, rza_wdt_of_match);
234
235 static struct platform_driver rza_wdt_driver = {
236 .probe = rza_wdt_probe,
237 .driver = {
238 .name = "rza_wdt",
239 .of_match_table = rza_wdt_of_match,
240 },
241 };
242
243 module_platform_driver(rza_wdt_driver);
244
245 MODULE_DESCRIPTION("Renesas RZ/A WDT Driver");
246 MODULE_AUTHOR("Chris Brandt <chris.brandt@renesas.com>");
247 MODULE_LICENSE("GPL v2");
248
