1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * PIC32 watchdog driver
4 *
5 * Joshua Henderson <joshua.henderson@microchip.com>
6 * Copyright (c) 2016, Microchip Technology Inc.
7 */
8 #include <linux/clk.h>
9 #include <linux/device.h>
10 #include <linux/err.h>
11 #include <linux/io.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/of_device.h>
16 #include <linux/platform_device.h>
17 #include <linux/pm.h>
18 #include <linux/watchdog.h>
19
20 #include <asm/mach-pic32/pic32.h>
21
22 /* Watchdog Timer Registers */
23 #define WDTCON_REG 0x00
24
25 /* Watchdog Timer Control Register fields */
26 #define WDTCON_WIN_EN BIT(0)
27 #define WDTCON_RMCS_MASK 0x0003
28 #define WDTCON_RMCS_SHIFT 0x0006
29 #define WDTCON_RMPS_MASK 0x001F
30 #define WDTCON_RMPS_SHIFT 0x0008
31 #define WDTCON_ON BIT(15)
32 #define WDTCON_CLR_KEY 0x5743
33
34 /* Reset Control Register fields for watchdog */
35 #define RESETCON_TIMEOUT_IDLE BIT(2)
36 #define RESETCON_TIMEOUT_SLEEP BIT(3)
37 #define RESETCON_WDT_TIMEOUT BIT(4)
38
39 struct pic32_wdt {
40 void __iomem *regs;
41 void __iomem *rst_base;
42 struct clk *clk;
43 };
44
pic32_wdt_is_win_enabled(struct pic32_wdt * wdt)45 static inline bool pic32_wdt_is_win_enabled(struct pic32_wdt *wdt)
46 {
47 return !!(readl(wdt->regs + WDTCON_REG) & WDTCON_WIN_EN);
48 }
49
pic32_wdt_get_post_scaler(struct pic32_wdt * wdt)50 static inline u32 pic32_wdt_get_post_scaler(struct pic32_wdt *wdt)
51 {
52 u32 v = readl(wdt->regs + WDTCON_REG);
53
54 return (v >> WDTCON_RMPS_SHIFT) & WDTCON_RMPS_MASK;
55 }
56
pic32_wdt_get_clk_id(struct pic32_wdt * wdt)57 static inline u32 pic32_wdt_get_clk_id(struct pic32_wdt *wdt)
58 {
59 u32 v = readl(wdt->regs + WDTCON_REG);
60
61 return (v >> WDTCON_RMCS_SHIFT) & WDTCON_RMCS_MASK;
62 }
63
pic32_wdt_bootstatus(struct pic32_wdt * wdt)64 static int pic32_wdt_bootstatus(struct pic32_wdt *wdt)
65 {
66 u32 v = readl(wdt->rst_base);
67
68 writel(RESETCON_WDT_TIMEOUT, PIC32_CLR(wdt->rst_base));
69
70 return v & RESETCON_WDT_TIMEOUT;
71 }
72
pic32_wdt_get_timeout_secs(struct pic32_wdt * wdt,struct device * dev)73 static u32 pic32_wdt_get_timeout_secs(struct pic32_wdt *wdt, struct device *dev)
74 {
75 unsigned long rate;
76 u32 period, ps, terminal;
77
78 rate = clk_get_rate(wdt->clk);
79
80 dev_dbg(dev, "wdt: clk_id %d, clk_rate %lu (prescale)\n",
81 pic32_wdt_get_clk_id(wdt), rate);
82
83 /* default, prescaler of 32 (i.e. div-by-32) is implicit. */
84 rate >>= 5;
85 if (!rate)
86 return 0;
87
88 /* calculate terminal count from postscaler. */
89 ps = pic32_wdt_get_post_scaler(wdt);
90 terminal = BIT(ps);
91
92 /* find time taken (in secs) to reach terminal count */
93 period = terminal / rate;
94 dev_dbg(dev,
95 "wdt: clk_rate %lu (postscale) / terminal %d, timeout %dsec\n",
96 rate, terminal, period);
97
98 return period;
99 }
100
pic32_wdt_keepalive(struct pic32_wdt * wdt)101 static void pic32_wdt_keepalive(struct pic32_wdt *wdt)
102 {
103 /* write key through single half-word */
104 writew(WDTCON_CLR_KEY, wdt->regs + WDTCON_REG + 2);
105 }
106
pic32_wdt_start(struct watchdog_device * wdd)107 static int pic32_wdt_start(struct watchdog_device *wdd)
108 {
109 struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
110
111 writel(WDTCON_ON, PIC32_SET(wdt->regs + WDTCON_REG));
112 pic32_wdt_keepalive(wdt);
113
114 return 0;
115 }
116
pic32_wdt_stop(struct watchdog_device * wdd)117 static int pic32_wdt_stop(struct watchdog_device *wdd)
118 {
119 struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
120
121 writel(WDTCON_ON, PIC32_CLR(wdt->regs + WDTCON_REG));
122
123 /*
124 * Cannot touch registers in the CPU cycle following clearing the
125 * ON bit.
126 */
127 nop();
128
129 return 0;
130 }
131
pic32_wdt_ping(struct watchdog_device * wdd)132 static int pic32_wdt_ping(struct watchdog_device *wdd)
133 {
134 struct pic32_wdt *wdt = watchdog_get_drvdata(wdd);
135
136 pic32_wdt_keepalive(wdt);
137
138 return 0;
139 }
140
141 static const struct watchdog_ops pic32_wdt_fops = {
142 .owner = THIS_MODULE,
143 .start = pic32_wdt_start,
144 .stop = pic32_wdt_stop,
145 .ping = pic32_wdt_ping,
146 };
147
148 static const struct watchdog_info pic32_wdt_ident = {
149 .options = WDIOF_KEEPALIVEPING |
150 WDIOF_MAGICCLOSE | WDIOF_CARDRESET,
151 .identity = "PIC32 Watchdog",
152 };
153
154 static struct watchdog_device pic32_wdd = {
155 .info = &pic32_wdt_ident,
156 .ops = &pic32_wdt_fops,
157 };
158
159 static const struct of_device_id pic32_wdt_dt_ids[] = {
160 { .compatible = "microchip,pic32mzda-wdt", },
161 { /* sentinel */ }
162 };
163 MODULE_DEVICE_TABLE(of, pic32_wdt_dt_ids);
164
pic32_clk_disable_unprepare(void * data)165 static void pic32_clk_disable_unprepare(void *data)
166 {
167 clk_disable_unprepare(data);
168 }
169
pic32_wdt_drv_probe(struct platform_device * pdev)170 static int pic32_wdt_drv_probe(struct platform_device *pdev)
171 {
172 struct device *dev = &pdev->dev;
173 int ret;
174 struct watchdog_device *wdd = &pic32_wdd;
175 struct pic32_wdt *wdt;
176
177 wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
178 if (!wdt)
179 return -ENOMEM;
180
181 wdt->regs = devm_platform_ioremap_resource(pdev, 0);
182 if (IS_ERR(wdt->regs))
183 return PTR_ERR(wdt->regs);
184
185 wdt->rst_base = devm_ioremap(dev, PIC32_BASE_RESET, 0x10);
186 if (!wdt->rst_base)
187 return -ENOMEM;
188
189 wdt->clk = devm_clk_get(dev, NULL);
190 if (IS_ERR(wdt->clk)) {
191 dev_err(dev, "clk not found\n");
192 return PTR_ERR(wdt->clk);
193 }
194
195 ret = clk_prepare_enable(wdt->clk);
196 if (ret) {
197 dev_err(dev, "clk enable failed\n");
198 return ret;
199 }
200 ret = devm_add_action_or_reset(dev, pic32_clk_disable_unprepare,
201 wdt->clk);
202 if (ret)
203 return ret;
204
205 if (pic32_wdt_is_win_enabled(wdt)) {
206 dev_err(dev, "windowed-clear mode is not supported.\n");
207 return -ENODEV;
208 }
209
210 wdd->timeout = pic32_wdt_get_timeout_secs(wdt, dev);
211 if (!wdd->timeout) {
212 dev_err(dev, "failed to read watchdog register timeout\n");
213 return -EINVAL;
214 }
215
216 dev_info(dev, "timeout %d\n", wdd->timeout);
217
218 wdd->bootstatus = pic32_wdt_bootstatus(wdt) ? WDIOF_CARDRESET : 0;
219
220 watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
221 watchdog_set_drvdata(wdd, wdt);
222
223 ret = devm_watchdog_register_device(dev, wdd);
224 if (ret)
225 return ret;
226
227 platform_set_drvdata(pdev, wdd);
228
229 return 0;
230 }
231
232 static struct platform_driver pic32_wdt_driver = {
233 .probe = pic32_wdt_drv_probe,
234 .driver = {
235 .name = "pic32-wdt",
236 .of_match_table = of_match_ptr(pic32_wdt_dt_ids),
237 }
238 };
239
240 module_platform_driver(pic32_wdt_driver);
241
242 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
243 MODULE_DESCRIPTION("Microchip PIC32 Watchdog Timer");
244 MODULE_LICENSE("GPL");
245
