1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * ARM Secure Monitor Call watchdog driver
4  *
5  * Copyright 2020 Google LLC.
6  * Julius Werner <jwerner@chromium.org>
7  * Based on mtk_wdt.c
8  */
9 
10 #include <linux/arm-smccc.h>
11 #include <linux/err.h>
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
14 #include <linux/of.h>
15 #include <linux/platform_device.h>
16 #include <linux/types.h>
17 #include <linux/watchdog.h>
18 #include <uapi/linux/psci.h>
19 
20 #define DRV_NAME		"arm_smc_wdt"
21 #define DRV_VERSION		"1.0"
22 
23 enum smcwd_call {
24 	SMCWD_INIT		= 0,
25 	SMCWD_SET_TIMEOUT	= 1,
26 	SMCWD_ENABLE		= 2,
27 	SMCWD_PET		= 3,
28 	SMCWD_GET_TIMELEFT	= 4,
29 };
30 
31 static bool nowayout = WATCHDOG_NOWAYOUT;
32 static unsigned int timeout;
33 
smcwd_call(struct watchdog_device * wdd,enum smcwd_call call,unsigned long arg,struct arm_smccc_res * res)34 static int smcwd_call(struct watchdog_device *wdd, enum smcwd_call call,
35 		      unsigned long arg, struct arm_smccc_res *res)
36 {
37 	struct arm_smccc_res local_res;
38 
39 	if (!res)
40 		res = &local_res;
41 
42 	arm_smccc_smc((u32)(uintptr_t)watchdog_get_drvdata(wdd), call, arg, 0,
43 		      0, 0, 0, 0, res);
44 
45 	if (res->a0 == PSCI_RET_NOT_SUPPORTED)
46 		return -ENODEV;
47 	if (res->a0 == PSCI_RET_INVALID_PARAMS)
48 		return -EINVAL;
49 	if (res->a0 != PSCI_RET_SUCCESS)
50 		return -EIO;
51 	return 0;
52 }
53 
smcwd_ping(struct watchdog_device * wdd)54 static int smcwd_ping(struct watchdog_device *wdd)
55 {
56 	return smcwd_call(wdd, SMCWD_PET, 0, NULL);
57 }
58 
smcwd_get_timeleft(struct watchdog_device * wdd)59 static unsigned int smcwd_get_timeleft(struct watchdog_device *wdd)
60 {
61 	struct arm_smccc_res res;
62 
63 	smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, &res);
64 	if (res.a0)
65 		return 0;
66 	return res.a1;
67 }
68 
smcwd_set_timeout(struct watchdog_device * wdd,unsigned int timeout)69 static int smcwd_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
70 {
71 	int res;
72 
73 	res = smcwd_call(wdd, SMCWD_SET_TIMEOUT, timeout, NULL);
74 	if (!res)
75 		wdd->timeout = timeout;
76 	return res;
77 }
78 
smcwd_stop(struct watchdog_device * wdd)79 static int smcwd_stop(struct watchdog_device *wdd)
80 {
81 	return smcwd_call(wdd, SMCWD_ENABLE, 0, NULL);
82 }
83 
smcwd_start(struct watchdog_device * wdd)84 static int smcwd_start(struct watchdog_device *wdd)
85 {
86 	return smcwd_call(wdd, SMCWD_ENABLE, 1, NULL);
87 }
88 
89 static const struct watchdog_info smcwd_info = {
90 	.identity	= DRV_NAME,
91 	.options	= WDIOF_SETTIMEOUT |
92 			  WDIOF_KEEPALIVEPING |
93 			  WDIOF_MAGICCLOSE,
94 };
95 
96 static const struct watchdog_ops smcwd_ops = {
97 	.start		= smcwd_start,
98 	.stop		= smcwd_stop,
99 	.ping		= smcwd_ping,
100 	.set_timeout	= smcwd_set_timeout,
101 };
102 
103 static const struct watchdog_ops smcwd_timeleft_ops = {
104 	.start		= smcwd_start,
105 	.stop		= smcwd_stop,
106 	.ping		= smcwd_ping,
107 	.set_timeout	= smcwd_set_timeout,
108 	.get_timeleft	= smcwd_get_timeleft,
109 };
110 
smcwd_probe(struct platform_device * pdev)111 static int smcwd_probe(struct platform_device *pdev)
112 {
113 	struct watchdog_device *wdd;
114 	int err;
115 	struct arm_smccc_res res;
116 	u32 smc_func_id;
117 
118 	wdd = devm_kzalloc(&pdev->dev, sizeof(*wdd), GFP_KERNEL);
119 	if (!wdd)
120 		return -ENOMEM;
121 	platform_set_drvdata(pdev, wdd);
122 
123 	if (of_property_read_u32(pdev->dev.of_node, "arm,smc-id",
124 				 &smc_func_id))
125 		smc_func_id = 0x82003D06;
126 	watchdog_set_drvdata(wdd, (void *)(uintptr_t)smc_func_id);
127 
128 	err = smcwd_call(wdd, SMCWD_INIT, 0, &res);
129 	if (err < 0)
130 		return err;
131 
132 	wdd->info = &smcwd_info;
133 	/* get_timeleft is optional */
134 	if (smcwd_call(wdd, SMCWD_GET_TIMELEFT, 0, NULL))
135 		wdd->ops = &smcwd_ops;
136 	else
137 		wdd->ops = &smcwd_timeleft_ops;
138 	wdd->timeout = res.a2;
139 	wdd->max_timeout = res.a2;
140 	wdd->min_timeout = res.a1;
141 	wdd->parent = &pdev->dev;
142 
143 	watchdog_stop_on_reboot(wdd);
144 	watchdog_stop_on_unregister(wdd);
145 	watchdog_set_nowayout(wdd, nowayout);
146 	watchdog_init_timeout(wdd, timeout, &pdev->dev);
147 	err = smcwd_set_timeout(wdd, wdd->timeout);
148 	if (err)
149 		return err;
150 
151 	err = devm_watchdog_register_device(&pdev->dev, wdd);
152 	if (err)
153 		return err;
154 
155 	dev_info(&pdev->dev,
156 		 "Watchdog registered (timeout=%d sec, nowayout=%d)\n",
157 		 wdd->timeout, nowayout);
158 
159 	return 0;
160 }
161 
162 static const struct of_device_id smcwd_dt_ids[] = {
163 	{ .compatible = "arm,smc-wdt" },
164 	{}
165 };
166 MODULE_DEVICE_TABLE(of, smcwd_dt_ids);
167 
168 static struct platform_driver smcwd_driver = {
169 	.probe		= smcwd_probe,
170 	.driver		= {
171 		.name		= DRV_NAME,
172 		.of_match_table	= smcwd_dt_ids,
173 	},
174 };
175 
176 module_platform_driver(smcwd_driver);
177 
178 module_param(timeout, uint, 0);
179 MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
180 
181 module_param(nowayout, bool, 0);
182 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
183 			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
184 
185 MODULE_LICENSE("GPL");
186 MODULE_AUTHOR("Julius Werner <jwerner@chromium.org>");
187 MODULE_DESCRIPTION("ARM Secure Monitor Call Watchdog Driver");
188 MODULE_VERSION(DRV_VERSION);
189