1 /*
2  * Generic Syscon Reboot Driver
3  *
4  * Copyright (c) 2013, Applied Micro Circuits Corporation
5  * Author: Feng Kan <fkan@apm.com>
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 as
9  * published by the Free Software Foundation; either version 2 of
10  * the License, or (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  */
17 #include <linux/delay.h>
18 #include <linux/io.h>
19 #include <linux/notifier.h>
20 #include <linux/mfd/syscon.h>
21 #include <linux/of_address.h>
22 #include <linux/of_device.h>
23 #include <linux/platform_device.h>
24 #include <linux/reboot.h>
25 #include <linux/regmap.h>
26 
27 struct syscon_reboot_context {
28 	struct regmap *map;
29 	u32 offset;
30 	u32 mask;
31 	struct notifier_block restart_handler;
32 };
33 
34 static int syscon_restart_handle(struct notifier_block *this,
35 					unsigned long mode, void *cmd)
36 {
37 	struct syscon_reboot_context *ctx =
38 			container_of(this, struct syscon_reboot_context,
39 					restart_handler);
40 
41 	/* Issue the reboot */
42 	regmap_write(ctx->map, ctx->offset, ctx->mask);
43 
44 	mdelay(1000);
45 
46 	pr_emerg("Unable to restart system\n");
47 	return NOTIFY_DONE;
48 }
49 
50 static int syscon_reboot_probe(struct platform_device *pdev)
51 {
52 	struct syscon_reboot_context *ctx;
53 	struct device *dev = &pdev->dev;
54 	int err;
55 
56 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
57 	if (!ctx)
58 		return -ENOMEM;
59 
60 	ctx->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
61 	if (IS_ERR(ctx->map))
62 		return PTR_ERR(ctx->map);
63 
64 	if (of_property_read_u32(pdev->dev.of_node, "offset", &ctx->offset))
65 		return -EINVAL;
66 
67 	if (of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask))
68 		return -EINVAL;
69 
70 	ctx->restart_handler.notifier_call = syscon_restart_handle;
71 	ctx->restart_handler.priority = 192;
72 	err = register_restart_handler(&ctx->restart_handler);
73 	if (err)
74 		dev_err(dev, "can't register restart notifier (err=%d)\n", err);
75 
76 	return err;
77 }
78 
79 static const struct of_device_id syscon_reboot_of_match[] = {
80 	{ .compatible = "syscon-reboot" },
81 	{}
82 };
83 
84 static struct platform_driver syscon_reboot_driver = {
85 	.probe = syscon_reboot_probe,
86 	.driver = {
87 		.name = "syscon-reboot",
88 		.of_match_table = syscon_reboot_of_match,
89 	},
90 };
91 builtin_platform_driver(syscon_reboot_driver);
92