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
18struct syscon_reboot_context {
19	struct regmap *map;
20	u32 offset;
21	u32 value;
22	u32 mask;
23	struct notifier_block restart_handler;
24};
25
26static 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
42static 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		ctx->map = syscon_node_to_regmap(dev->parent->of_node);
56		if (IS_ERR(ctx->map))
57			return PTR_ERR(ctx->map);
58	}
59
60	if (of_property_read_u32(pdev->dev.of_node, "offset", &ctx->offset))
61		return -EINVAL;
62
63	value_err = of_property_read_u32(pdev->dev.of_node, "value", &ctx->value);
64	mask_err = of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask);
65	if (value_err && mask_err) {
66		dev_err(dev, "unable to read 'value' and 'mask'");
67		return -EINVAL;
68	}
69
70	if (value_err) {
71		/* support old binding */
72		ctx->value = ctx->mask;
73		ctx->mask = 0xFFFFFFFF;
74	} else if (mask_err) {
75		/* support value without mask*/
76		ctx->mask = 0xFFFFFFFF;
77	}
78
79	ctx->restart_handler.notifier_call = syscon_restart_handle;
80	ctx->restart_handler.priority = 192;
81	err = register_restart_handler(&ctx->restart_handler);
82	if (err)
83		dev_err(dev, "can't register restart notifier (err=%d)\n", err);
84
85	return err;
86}
87
88static const struct of_device_id syscon_reboot_of_match[] = {
89	{ .compatible = "syscon-reboot" },
90	{}
91};
92
93static struct platform_driver syscon_reboot_driver = {
94	.probe = syscon_reboot_probe,
95	.driver = {
96		.name = "syscon-reboot",
97		.of_match_table = syscon_reboot_of_match,
98	},
99};
100builtin_platform_driver(syscon_reboot_driver);
101