1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Generic Syscon Reboot Driver
4  *
5  * Copyright (c) 2013, Applied Micro Circuits Corporation
6  * Author: Feng Kan <fkan@apm.com>
7  */
8 #include <linux/delay.h>
9 #include <linux/io.h>
10 #include <linux/notifier.h>
11 #include <linux/mfd/syscon.h>
12 #include <linux/of_address.h>
13 #include <linux/of_device.h>
14 #include <linux/platform_device.h>
15 #include <linux/reboot.h>
16 #include <linux/regmap.h>
17 
18 struct syscon_reboot_context {
19 	struct regmap *map;
20 	u32 offset;
21 	u32 value;
22 	u32 mask;
23 	struct notifier_block restart_handler;
24 };
25 
26 static int syscon_restart_handle(struct notifier_block *this,
27 					unsigned long mode, void *cmd)
28 {
29 	struct syscon_reboot_context *ctx =
30 			container_of(this, struct syscon_reboot_context,
31 					restart_handler);
32 
33 	/* Issue the reboot */
34 	regmap_update_bits(ctx->map, ctx->offset, ctx->mask, ctx->value);
35 
36 	mdelay(1000);
37 
38 	pr_emerg("Unable to restart system\n");
39 	return NOTIFY_DONE;
40 }
41 
42 static int syscon_reboot_probe(struct platform_device *pdev)
43 {
44 	struct syscon_reboot_context *ctx;
45 	struct device *dev = &pdev->dev;
46 	int mask_err, value_err;
47 	int err;
48 
49 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
50 	if (!ctx)
51 		return -ENOMEM;
52 
53 	ctx->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
54 	if (IS_ERR(ctx->map))
55 		return PTR_ERR(ctx->map);
56 
57 	if (of_property_read_u32(pdev->dev.of_node, "offset", &ctx->offset))
58 		return -EINVAL;
59 
60 	value_err = of_property_read_u32(pdev->dev.of_node, "value", &ctx->value);
61 	mask_err = of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask);
62 	if (value_err && mask_err) {
63 		dev_err(dev, "unable to read 'value' and 'mask'");
64 		return -EINVAL;
65 	}
66 
67 	if (value_err) {
68 		/* support old binding */
69 		ctx->value = ctx->mask;
70 		ctx->mask = 0xFFFFFFFF;
71 	} else if (mask_err) {
72 		/* support value without mask*/
73 		ctx->mask = 0xFFFFFFFF;
74 	}
75 
76 	ctx->restart_handler.notifier_call = syscon_restart_handle;
77 	ctx->restart_handler.priority = 192;
78 	err = register_restart_handler(&ctx->restart_handler);
79 	if (err)
80 		dev_err(dev, "can't register restart notifier (err=%d)\n", err);
81 
82 	return err;
83 }
84 
85 static const struct of_device_id syscon_reboot_of_match[] = {
86 	{ .compatible = "syscon-reboot" },
87 	{}
88 };
89 
90 static struct platform_driver syscon_reboot_driver = {
91 	.probe = syscon_reboot_probe,
92 	.driver = {
93 		.name = "syscon-reboot",
94 		.of_match_table = syscon_reboot_of_match,
95 	},
96 };
97 builtin_platform_driver(syscon_reboot_driver);
98