xref: /linux/drivers/watchdog/pic32-dmt.c (revision 80d443e8876602be2c130f79c4de81e12e2a700d) 
1 /*
2  * PIC32 deadman timer driver
3  *
4  * Purna Chandra Mandal <purna.mandal@microchip.com>
5  * Copyright (c) 2016, Microchip Technology Inc.
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version
10  * 2 of the License, or (at your option) any later version.
11  */
12 #include <linux/clk.h>
13 #include <linux/device.h>
14 #include <linux/err.h>
15 #include <linux/io.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/of.h>
19 #include <linux/of_device.h>
20 #include <linux/platform_device.h>
21 #include <linux/pm.h>
22 #include <linux/watchdog.h>
23 
24 #include <asm/mach-pic32/pic32.h>
25 
26 /* Deadman Timer Regs */
27 #define DMTCON_REG	0x00
28 #define DMTPRECLR_REG	0x10
29 #define DMTCLR_REG	0x20
30 #define DMTSTAT_REG	0x30
31 #define DMTCNT_REG	0x40
32 #define DMTPSCNT_REG	0x60
33 #define DMTPSINTV_REG	0x70
34 
35 /* Deadman Timer Regs fields */
36 #define DMT_ON			BIT(15)
37 #define DMT_STEP1_KEY		BIT(6)
38 #define DMT_STEP2_KEY		BIT(3)
39 #define DMTSTAT_WINOPN		BIT(0)
40 #define DMTSTAT_EVENT		BIT(5)
41 #define DMTSTAT_BAD2		BIT(6)
42 #define DMTSTAT_BAD1		BIT(7)
43 
44 /* Reset Control Register fields for watchdog */
45 #define RESETCON_DMT_TIMEOUT	BIT(5)
46 
47 struct pic32_dmt {
48 	void __iomem	*regs;
49 	struct clk	*clk;
50 };
51 
52 static inline void dmt_enable(struct pic32_dmt *dmt)
53 {
54 	writel(DMT_ON, PIC32_SET(dmt->regs + DMTCON_REG));
55 }
56 
57 static inline void dmt_disable(struct pic32_dmt *dmt)
58 {
59 	writel(DMT_ON, PIC32_CLR(dmt->regs + DMTCON_REG));
60 	/*
61 	 * Cannot touch registers in the CPU cycle following clearing the
62 	 * ON bit.
63 	 */
64 	nop();
65 }
66 
67 static inline int dmt_bad_status(struct pic32_dmt *dmt)
68 {
69 	u32 val;
70 
71 	val = readl(dmt->regs + DMTSTAT_REG);
72 	val &= (DMTSTAT_BAD1 | DMTSTAT_BAD2 | DMTSTAT_EVENT);
73 	if (val)
74 		return -EAGAIN;
75 
76 	return 0;
77 }
78 
79 static inline int dmt_keepalive(struct pic32_dmt *dmt)
80 {
81 	u32 v;
82 	u32 timeout = 500;
83 
84 	/* set pre-clear key */
85 	writel(DMT_STEP1_KEY << 8, dmt->regs + DMTPRECLR_REG);
86 
87 	/* wait for DMT window to open */
88 	while (--timeout) {
89 		v = readl(dmt->regs + DMTSTAT_REG) & DMTSTAT_WINOPN;
90 		if (v == DMTSTAT_WINOPN)
91 			break;
92 	}
93 
94 	/* apply key2 */
95 	writel(DMT_STEP2_KEY, dmt->regs + DMTCLR_REG);
96 
97 	/* check whether keys are latched correctly */
98 	return dmt_bad_status(dmt);
99 }
100 
101 static inline u32 pic32_dmt_get_timeout_secs(struct pic32_dmt *dmt)
102 {
103 	unsigned long rate;
104 
105 	rate = clk_get_rate(dmt->clk);
106 	if (rate)
107 		return readl(dmt->regs + DMTPSCNT_REG) / rate;
108 
109 	return 0;
110 }
111 
112 static inline u32 pic32_dmt_bootstatus(struct pic32_dmt *dmt)
113 {
114 	u32 v;
115 	void __iomem *rst_base;
116 
117 	rst_base = ioremap(PIC32_BASE_RESET, 0x10);
118 	if (!rst_base)
119 		return 0;
120 
121 	v = readl(rst_base);
122 
123 	writel(RESETCON_DMT_TIMEOUT, PIC32_CLR(rst_base));
124 
125 	iounmap(rst_base);
126 	return v & RESETCON_DMT_TIMEOUT;
127 }
128 
129 static int pic32_dmt_start(struct watchdog_device *wdd)
130 {
131 	struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
132 
133 	dmt_enable(dmt);
134 	return dmt_keepalive(dmt);
135 }
136 
137 static int pic32_dmt_stop(struct watchdog_device *wdd)
138 {
139 	struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
140 
141 	dmt_disable(dmt);
142 
143 	return 0;
144 }
145 
146 static int pic32_dmt_ping(struct watchdog_device *wdd)
147 {
148 	struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
149 
150 	return dmt_keepalive(dmt);
151 }
152 
153 static const struct watchdog_ops pic32_dmt_fops = {
154 	.owner		= THIS_MODULE,
155 	.start		= pic32_dmt_start,
156 	.stop		= pic32_dmt_stop,
157 	.ping		= pic32_dmt_ping,
158 };
159 
160 static const struct watchdog_info pic32_dmt_ident = {
161 	.options	= WDIOF_KEEPALIVEPING |
162 			  WDIOF_MAGICCLOSE,
163 	.identity	= "PIC32 Deadman Timer",
164 };
165 
166 static struct watchdog_device pic32_dmt_wdd = {
167 	.info		= &pic32_dmt_ident,
168 	.ops		= &pic32_dmt_fops,
169 };
170 
171 static int pic32_dmt_probe(struct platform_device *pdev)
172 {
173 	int ret;
174 	struct pic32_dmt *dmt;
175 	struct resource *mem;
176 	struct watchdog_device *wdd = &pic32_dmt_wdd;
177 
178 	dmt = devm_kzalloc(&pdev->dev, sizeof(*dmt), GFP_KERNEL);
179 	if (!dmt)
180 		return -ENOMEM;
181 
182 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
183 	dmt->regs = devm_ioremap_resource(&pdev->dev, mem);
184 	if (IS_ERR(dmt->regs))
185 		return PTR_ERR(dmt->regs);
186 
187 	dmt->clk = devm_clk_get(&pdev->dev, NULL);
188 	if (IS_ERR(dmt->clk)) {
189 		dev_err(&pdev->dev, "clk not found\n");
190 		return PTR_ERR(dmt->clk);
191 	}
192 
193 	ret = clk_prepare_enable(dmt->clk);
194 	if (ret)
195 		return ret;
196 
197 	wdd->timeout = pic32_dmt_get_timeout_secs(dmt);
198 	if (!wdd->timeout) {
199 		dev_err(&pdev->dev,
200 			"failed to read watchdog register timeout\n");
201 		ret = -EINVAL;
202 		goto out_disable_clk;
203 	}
204 
205 	dev_info(&pdev->dev, "timeout %d\n", wdd->timeout);
206 
207 	wdd->bootstatus = pic32_dmt_bootstatus(dmt) ? WDIOF_CARDRESET : 0;
208 
209 	watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
210 	watchdog_set_drvdata(wdd, dmt);
211 
212 	ret = watchdog_register_device(wdd);
213 	if (ret) {
214 		dev_err(&pdev->dev, "watchdog register failed, err %d\n", ret);
215 		goto out_disable_clk;
216 	}
217 
218 	platform_set_drvdata(pdev, wdd);
219 	return 0;
220 
221 out_disable_clk:
222 	clk_disable_unprepare(dmt->clk);
223 	return ret;
224 }
225 
226 static int pic32_dmt_remove(struct platform_device *pdev)
227 {
228 	struct watchdog_device *wdd = platform_get_drvdata(pdev);
229 	struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
230 
231 	watchdog_unregister_device(wdd);
232 	clk_disable_unprepare(dmt->clk);
233 
234 	return 0;
235 }
236 
237 static const struct of_device_id pic32_dmt_of_ids[] = {
238 	{ .compatible = "microchip,pic32mzda-dmt",},
239 	{ /* sentinel */ }
240 };
241 MODULE_DEVICE_TABLE(of, pic32_dmt_of_ids);
242 
243 static struct platform_driver pic32_dmt_driver = {
244 	.probe		= pic32_dmt_probe,
245 	.remove		= pic32_dmt_remove,
246 	.driver		= {
247 		.name		= "pic32-dmt",
248 		.of_match_table = of_match_ptr(pic32_dmt_of_ids),
249 	}
250 };
251 
252 module_platform_driver(pic32_dmt_driver);
253 
254 MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@microchip.com>");
255 MODULE_DESCRIPTION("Microchip PIC32 DMT Driver");
256 MODULE_LICENSE("GPL");
257