1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * wm831x-otp.c  --  OTP for Wolfson WM831x PMICs
4  *
5  * Copyright 2009 Wolfson Microelectronics PLC.
6  *
7  * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/i2c.h>
13 #include <linux/bcd.h>
14 #include <linux/delay.h>
15 #include <linux/mfd/core.h>
16 #include <linux/random.h>
17 
18 #include <linux/mfd/wm831x/core.h>
19 #include <linux/mfd/wm831x/otp.h>
20 
21 /* In bytes */
22 #define WM831X_UNIQUE_ID_LEN 16
23 
24 /* Read the unique ID from the chip into id */
wm831x_unique_id_read(struct wm831x * wm831x,char * id)25 static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
26 {
27 	int i, val;
28 
29 	for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
30 		val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
31 		if (val < 0)
32 			return val;
33 
34 		id[i * 2]       = (val >> 8) & 0xff;
35 		id[(i * 2) + 1] = val & 0xff;
36 	}
37 
38 	return 0;
39 }
40 
unique_id_show(struct device * dev,struct device_attribute * attr,char * buf)41 static ssize_t unique_id_show(struct device *dev,
42 			      struct device_attribute *attr, char *buf)
43 {
44 	struct wm831x *wm831x = dev_get_drvdata(dev);
45 	int rval;
46 	char id[WM831X_UNIQUE_ID_LEN];
47 
48 	rval = wm831x_unique_id_read(wm831x, id);
49 	if (rval < 0)
50 		return 0;
51 
52 	return sprintf(buf, "%*phN\n", WM831X_UNIQUE_ID_LEN, id);
53 }
54 
55 static DEVICE_ATTR_RO(unique_id);
56 
wm831x_otp_init(struct wm831x * wm831x)57 int wm831x_otp_init(struct wm831x *wm831x)
58 {
59 	char uuid[WM831X_UNIQUE_ID_LEN];
60 	int ret;
61 
62 	ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
63 	if (ret != 0)
64 		dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
65 			ret);
66 
67 	ret = wm831x_unique_id_read(wm831x, uuid);
68 	if (ret == 0)
69 		add_device_randomness(uuid, sizeof(uuid));
70 	else
71 		dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
72 
73 	return ret;
74 }
75 
wm831x_otp_exit(struct wm831x * wm831x)76 void wm831x_otp_exit(struct wm831x *wm831x)
77 {
78 	device_remove_file(wm831x->dev, &dev_attr_unique_id);
79 }
80 
81