1 /*
2  * Reset driver for Axxia devices
3  *
4  * Copyright (C) 2014 LSI
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 and
8  * only version 2 as published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  */
16 #include <linux/init.h>
17 #include <linux/err.h>
18 #include <linux/io.h>
19 #include <linux/kernel.h>
20 #include <linux/mfd/syscon.h>
21 #include <linux/module.h>
22 #include <linux/notifier.h>
23 #include <linux/of.h>
24 #include <linux/platform_device.h>
25 #include <linux/reboot.h>
26 #include <linux/regmap.h>
27 
28 #define SC_CRIT_WRITE_KEY	0x1000
29 #define SC_LATCH_ON_RESET	0x1004
30 #define SC_RESET_CONTROL	0x1008
31 #define   RSTCTL_RST_ZERO	(1<<3)
32 #define   RSTCTL_RST_FAB	(1<<2)
33 #define   RSTCTL_RST_CHIP	(1<<1)
34 #define   RSTCTL_RST_SYS	(1<<0)
35 #define SC_EFUSE_INT_STATUS	0x180c
36 #define   EFUSE_READ_DONE	(1<<31)
37 
38 static struct regmap *syscon;
39 
40 static int axxia_restart_handler(struct notifier_block *this,
41 				 unsigned long mode, void *cmd)
42 {
43 	/* Access Key (0xab) */
44 	regmap_write(syscon, SC_CRIT_WRITE_KEY, 0xab);
45 	/* Select internal boot from 0xffff0000 */
46 	regmap_write(syscon, SC_LATCH_ON_RESET, 0x00000040);
47 	/* Assert ResetReadDone (to avoid hanging in boot ROM) */
48 	regmap_write(syscon, SC_EFUSE_INT_STATUS, EFUSE_READ_DONE);
49 	/* Assert chip reset */
50 	regmap_update_bits(syscon, SC_RESET_CONTROL,
51 			   RSTCTL_RST_CHIP, RSTCTL_RST_CHIP);
52 
53 	return NOTIFY_DONE;
54 }
55 
56 static struct notifier_block axxia_restart_nb = {
57 	.notifier_call = axxia_restart_handler,
58 	.priority = 128,
59 };
60 
61 static int axxia_reset_probe(struct platform_device *pdev)
62 {
63 	struct device *dev = &pdev->dev;
64 	int err;
65 
66 	syscon = syscon_regmap_lookup_by_phandle(dev->of_node, "syscon");
67 	if (IS_ERR(syscon)) {
68 		pr_err("%pOFn: syscon lookup failed\n", dev->of_node);
69 		return PTR_ERR(syscon);
70 	}
71 
72 	err = register_restart_handler(&axxia_restart_nb);
73 	if (err)
74 		dev_err(dev, "cannot register restart handler (err=%d)\n", err);
75 
76 	return err;
77 }
78 
79 static const struct of_device_id of_axxia_reset_match[] = {
80 	{ .compatible = "lsi,axm55xx-reset", },
81 	{},
82 };
83 MODULE_DEVICE_TABLE(of, of_axxia_reset_match);
84 
85 static struct platform_driver axxia_reset_driver = {
86 	.probe = axxia_reset_probe,
87 	.driver = {
88 		.name = "axxia-reset",
89 		.of_match_table = of_match_ptr(of_axxia_reset_match),
90 	},
91 };
92 
93 static int __init axxia_reset_init(void)
94 {
95 	return platform_driver_register(&axxia_reset_driver);
96 }
97 device_initcall(axxia_reset_init);
98