1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * PIC32 deadman timer driver
4 *
5 * Purna Chandra Mandal <purna.mandal@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 /* Deadman Timer Regs */
23 #define DMTCON_REG 0x00
24 #define DMTPRECLR_REG 0x10
25 #define DMTCLR_REG 0x20
26 #define DMTSTAT_REG 0x30
27 #define DMTCNT_REG 0x40
28 #define DMTPSCNT_REG 0x60
29 #define DMTPSINTV_REG 0x70
30
31 /* Deadman Timer Regs fields */
32 #define DMT_ON BIT(15)
33 #define DMT_STEP1_KEY BIT(6)
34 #define DMT_STEP2_KEY BIT(3)
35 #define DMTSTAT_WINOPN BIT(0)
36 #define DMTSTAT_EVENT BIT(5)
37 #define DMTSTAT_BAD2 BIT(6)
38 #define DMTSTAT_BAD1 BIT(7)
39
40 /* Reset Control Register fields for watchdog */
41 #define RESETCON_DMT_TIMEOUT BIT(5)
42
43 struct pic32_dmt {
44 void __iomem *regs;
45 struct clk *clk;
46 };
47
dmt_enable(struct pic32_dmt * dmt)48 static inline void dmt_enable(struct pic32_dmt *dmt)
49 {
50 writel(DMT_ON, PIC32_SET(dmt->regs + DMTCON_REG));
51 }
52
dmt_disable(struct pic32_dmt * dmt)53 static inline void dmt_disable(struct pic32_dmt *dmt)
54 {
55 writel(DMT_ON, PIC32_CLR(dmt->regs + DMTCON_REG));
56 /*
57 * Cannot touch registers in the CPU cycle following clearing the
58 * ON bit.
59 */
60 nop();
61 }
62
dmt_bad_status(struct pic32_dmt * dmt)63 static inline int dmt_bad_status(struct pic32_dmt *dmt)
64 {
65 u32 val;
66
67 val = readl(dmt->regs + DMTSTAT_REG);
68 val &= (DMTSTAT_BAD1 | DMTSTAT_BAD2 | DMTSTAT_EVENT);
69 if (val)
70 return -EAGAIN;
71
72 return 0;
73 }
74
dmt_keepalive(struct pic32_dmt * dmt)75 static inline int dmt_keepalive(struct pic32_dmt *dmt)
76 {
77 u32 v;
78 u32 timeout = 500;
79
80 /* set pre-clear key */
81 writel(DMT_STEP1_KEY << 8, dmt->regs + DMTPRECLR_REG);
82
83 /* wait for DMT window to open */
84 while (--timeout) {
85 v = readl(dmt->regs + DMTSTAT_REG) & DMTSTAT_WINOPN;
86 if (v == DMTSTAT_WINOPN)
87 break;
88 }
89
90 /* apply key2 */
91 writel(DMT_STEP2_KEY, dmt->regs + DMTCLR_REG);
92
93 /* check whether keys are latched correctly */
94 return dmt_bad_status(dmt);
95 }
96
pic32_dmt_get_timeout_secs(struct pic32_dmt * dmt)97 static inline u32 pic32_dmt_get_timeout_secs(struct pic32_dmt *dmt)
98 {
99 unsigned long rate;
100
101 rate = clk_get_rate(dmt->clk);
102 if (rate)
103 return readl(dmt->regs + DMTPSCNT_REG) / rate;
104
105 return 0;
106 }
107
pic32_dmt_bootstatus(struct pic32_dmt * dmt)108 static inline u32 pic32_dmt_bootstatus(struct pic32_dmt *dmt)
109 {
110 u32 v;
111 void __iomem *rst_base;
112
113 rst_base = ioremap(PIC32_BASE_RESET, 0x10);
114 if (!rst_base)
115 return 0;
116
117 v = readl(rst_base);
118
119 writel(RESETCON_DMT_TIMEOUT, PIC32_CLR(rst_base));
120
121 iounmap(rst_base);
122 return v & RESETCON_DMT_TIMEOUT;
123 }
124
pic32_dmt_start(struct watchdog_device * wdd)125 static int pic32_dmt_start(struct watchdog_device *wdd)
126 {
127 struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
128
129 dmt_enable(dmt);
130 return dmt_keepalive(dmt);
131 }
132
pic32_dmt_stop(struct watchdog_device * wdd)133 static int pic32_dmt_stop(struct watchdog_device *wdd)
134 {
135 struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
136
137 dmt_disable(dmt);
138
139 return 0;
140 }
141
pic32_dmt_ping(struct watchdog_device * wdd)142 static int pic32_dmt_ping(struct watchdog_device *wdd)
143 {
144 struct pic32_dmt *dmt = watchdog_get_drvdata(wdd);
145
146 return dmt_keepalive(dmt);
147 }
148
149 static const struct watchdog_ops pic32_dmt_fops = {
150 .owner = THIS_MODULE,
151 .start = pic32_dmt_start,
152 .stop = pic32_dmt_stop,
153 .ping = pic32_dmt_ping,
154 };
155
156 static const struct watchdog_info pic32_dmt_ident = {
157 .options = WDIOF_KEEPALIVEPING |
158 WDIOF_MAGICCLOSE,
159 .identity = "PIC32 Deadman Timer",
160 };
161
162 static struct watchdog_device pic32_dmt_wdd = {
163 .info = &pic32_dmt_ident,
164 .ops = &pic32_dmt_fops,
165 };
166
pic32_clk_disable_unprepare(void * data)167 static void pic32_clk_disable_unprepare(void *data)
168 {
169 clk_disable_unprepare(data);
170 }
171
pic32_dmt_probe(struct platform_device * pdev)172 static int pic32_dmt_probe(struct platform_device *pdev)
173 {
174 struct device *dev = &pdev->dev;
175 int ret;
176 struct pic32_dmt *dmt;
177 struct watchdog_device *wdd = &pic32_dmt_wdd;
178
179 dmt = devm_kzalloc(dev, sizeof(*dmt), GFP_KERNEL);
180 if (!dmt)
181 return -ENOMEM;
182
183 dmt->regs = devm_platform_ioremap_resource(pdev, 0);
184 if (IS_ERR(dmt->regs))
185 return PTR_ERR(dmt->regs);
186
187 dmt->clk = devm_clk_get(dev, NULL);
188 if (IS_ERR(dmt->clk)) {
189 dev_err(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 ret = devm_add_action_or_reset(dev, pic32_clk_disable_unprepare,
197 dmt->clk);
198 if (ret)
199 return ret;
200
201 wdd->timeout = pic32_dmt_get_timeout_secs(dmt);
202 if (!wdd->timeout) {
203 dev_err(dev, "failed to read watchdog register timeout\n");
204 return -EINVAL;
205 }
206
207 dev_info(dev, "timeout %d\n", wdd->timeout);
208
209 wdd->bootstatus = pic32_dmt_bootstatus(dmt) ? WDIOF_CARDRESET : 0;
210
211 watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
212 watchdog_set_drvdata(wdd, dmt);
213
214 ret = devm_watchdog_register_device(dev, wdd);
215 if (ret)
216 return ret;
217
218 platform_set_drvdata(pdev, wdd);
219 return 0;
220 }
221
222 static const struct of_device_id pic32_dmt_of_ids[] = {
223 { .compatible = "microchip,pic32mzda-dmt",},
224 { /* sentinel */ }
225 };
226 MODULE_DEVICE_TABLE(of, pic32_dmt_of_ids);
227
228 static struct platform_driver pic32_dmt_driver = {
229 .probe = pic32_dmt_probe,
230 .driver = {
231 .name = "pic32-dmt",
232 .of_match_table = of_match_ptr(pic32_dmt_of_ids),
233 }
234 };
235
236 module_platform_driver(pic32_dmt_driver);
237
238 MODULE_AUTHOR("Purna Chandra Mandal <purna.mandal@microchip.com>");
239 MODULE_DESCRIPTION("Microchip PIC32 DMT Driver");
240 MODULE_LICENSE("GPL");
241