1 /*
2  *      intel-mid_wdt: generic Intel MID SCU watchdog driver
3  *
4  *      Platforms supported so far:
5  *      - Merrifield only
6  *
7  *      Copyright (C) 2014 Intel Corporation. All rights reserved.
8  *      Contact: David Cohen <david.a.cohen@linux.intel.com>
9  *
10  *      This program is free software; you can redistribute it and/or
11  *      modify it under the terms of version 2 of the GNU General
12  *      Public License as published by the Free Software Foundation.
13  */
14 
15 #include <linux/interrupt.h>
16 #include <linux/module.h>
17 #include <linux/nmi.h>
18 #include <linux/platform_device.h>
19 #include <linux/watchdog.h>
20 #include <linux/platform_data/intel-mid_wdt.h>
21 
22 #include <asm/intel_scu_ipc.h>
23 #include <asm/intel-mid.h>
24 
25 #define IPC_WATCHDOG 0xf8
26 
27 #define MID_WDT_PRETIMEOUT		15
28 #define MID_WDT_TIMEOUT_MIN		(1 + MID_WDT_PRETIMEOUT)
29 #define MID_WDT_TIMEOUT_MAX		170
30 #define MID_WDT_DEFAULT_TIMEOUT		90
31 
32 /* SCU watchdog messages */
33 enum {
34 	SCU_WATCHDOG_START = 0,
35 	SCU_WATCHDOG_STOP,
36 	SCU_WATCHDOG_KEEPALIVE,
37 };
38 
39 static inline int wdt_command(int sub, u32 *in, int inlen)
40 {
41 	return intel_scu_ipc_command(IPC_WATCHDOG, sub, in, inlen, NULL, 0);
42 }
43 
44 static int wdt_start(struct watchdog_device *wd)
45 {
46 	struct device *dev = watchdog_get_drvdata(wd);
47 	int ret, in_size;
48 	int timeout = wd->timeout;
49 	struct ipc_wd_start {
50 		u32 pretimeout;
51 		u32 timeout;
52 	} ipc_wd_start = { timeout - MID_WDT_PRETIMEOUT, timeout };
53 
54 	/*
55 	 * SCU expects the input size for watchdog IPC to
56 	 * be based on 4 bytes
57 	 */
58 	in_size = DIV_ROUND_UP(sizeof(ipc_wd_start), 4);
59 
60 	ret = wdt_command(SCU_WATCHDOG_START, (u32 *)&ipc_wd_start, in_size);
61 	if (ret)
62 		dev_crit(dev, "error starting watchdog: %d\n", ret);
63 
64 	return ret;
65 }
66 
67 static int wdt_ping(struct watchdog_device *wd)
68 {
69 	struct device *dev = watchdog_get_drvdata(wd);
70 	int ret;
71 
72 	ret = wdt_command(SCU_WATCHDOG_KEEPALIVE, NULL, 0);
73 	if (ret)
74 		dev_crit(dev, "Error executing keepalive: %d\n", ret);
75 
76 	return ret;
77 }
78 
79 static int wdt_stop(struct watchdog_device *wd)
80 {
81 	struct device *dev = watchdog_get_drvdata(wd);
82 	int ret;
83 
84 	ret = wdt_command(SCU_WATCHDOG_STOP, NULL, 0);
85 	if (ret)
86 		dev_crit(dev, "Error stopping watchdog: %d\n", ret);
87 
88 	return ret;
89 }
90 
91 static irqreturn_t mid_wdt_irq(int irq, void *dev_id)
92 {
93 	panic("Kernel Watchdog");
94 
95 	/* This code should not be reached */
96 	return IRQ_HANDLED;
97 }
98 
99 static const struct watchdog_info mid_wdt_info = {
100 	.identity = "Intel MID SCU watchdog",
101 	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
102 };
103 
104 static const struct watchdog_ops mid_wdt_ops = {
105 	.owner = THIS_MODULE,
106 	.start = wdt_start,
107 	.stop = wdt_stop,
108 	.ping = wdt_ping,
109 };
110 
111 static int mid_wdt_probe(struct platform_device *pdev)
112 {
113 	struct device *dev = &pdev->dev;
114 	struct watchdog_device *wdt_dev;
115 	struct intel_mid_wdt_pdata *pdata = dev->platform_data;
116 	int ret;
117 
118 	if (!pdata) {
119 		dev_err(dev, "missing platform data\n");
120 		return -EINVAL;
121 	}
122 
123 	if (pdata->probe) {
124 		ret = pdata->probe(pdev);
125 		if (ret)
126 			return ret;
127 	}
128 
129 	wdt_dev = devm_kzalloc(dev, sizeof(*wdt_dev), GFP_KERNEL);
130 	if (!wdt_dev)
131 		return -ENOMEM;
132 
133 	wdt_dev->info = &mid_wdt_info;
134 	wdt_dev->ops = &mid_wdt_ops;
135 	wdt_dev->min_timeout = MID_WDT_TIMEOUT_MIN;
136 	wdt_dev->max_timeout = MID_WDT_TIMEOUT_MAX;
137 	wdt_dev->timeout = MID_WDT_DEFAULT_TIMEOUT;
138 	wdt_dev->parent = dev;
139 
140 	watchdog_set_drvdata(wdt_dev, dev);
141 
142 	ret = devm_request_irq(dev, pdata->irq, mid_wdt_irq,
143 			       IRQF_SHARED | IRQF_NO_SUSPEND, "watchdog",
144 			       wdt_dev);
145 	if (ret) {
146 		dev_err(dev, "error requesting warning irq %d\n", pdata->irq);
147 		return ret;
148 	}
149 
150 	/*
151 	 * The firmware followed by U-Boot leaves the watchdog running
152 	 * with the default threshold which may vary. When we get here
153 	 * we should make a decision to prevent any side effects before
154 	 * user space daemon will take care of it. The best option,
155 	 * taking into consideration that there is no way to read values
156 	 * back from hardware, is to enforce watchdog being run with
157 	 * deterministic values.
158 	 */
159 	ret = wdt_start(wdt_dev);
160 	if (ret)
161 		return ret;
162 
163 	/* Make sure the watchdog is serviced */
164 	set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
165 
166 	ret = devm_watchdog_register_device(dev, wdt_dev);
167 	if (ret) {
168 		dev_err(dev, "error registering watchdog device\n");
169 		return ret;
170 	}
171 
172 	dev_info(dev, "Intel MID watchdog device probed\n");
173 
174 	return 0;
175 }
176 
177 static struct platform_driver mid_wdt_driver = {
178 	.probe		= mid_wdt_probe,
179 	.driver		= {
180 		.name	= "intel_mid_wdt",
181 	},
182 };
183 
184 module_platform_driver(mid_wdt_driver);
185 
186 MODULE_AUTHOR("David Cohen <david.a.cohen@linux.intel.com>");
187 MODULE_DESCRIPTION("Watchdog Driver for Intel MID platform");
188 MODULE_LICENSE("GPL");
189