1 /*
2 * wm831x-otp.c -- OTP for Wolfson WM831x PMICs
3 *
4 * Copyright 2009 Wolfson Microelectronics PLC.
5 *
6 * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License as published by the
10 * Free Software Foundation; either version 2 of the License, or (at your
11 * option) any later version.
12 *
13 */
14
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/i2c.h>
18 #include <linux/bcd.h>
19 #include <linux/delay.h>
20 #include <linux/mfd/core.h>
21 #include <linux/random.h>
22
23 #include <linux/mfd/wm831x/core.h>
24 #include <linux/mfd/wm831x/otp.h>
25
26 /* In bytes */
27 #define WM831X_UNIQUE_ID_LEN 16
28
29 /* Read the unique ID from the chip into id */
wm831x_unique_id_read(struct wm831x * wm831x,char * id)30 static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
31 {
32 int i, val;
33
34 for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
35 val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
36 if (val < 0)
37 return val;
38
39 id[i * 2] = (val >> 8) & 0xff;
40 id[(i * 2) + 1] = val & 0xff;
41 }
42
43 return 0;
44 }
45
wm831x_unique_id_show(struct device * dev,struct device_attribute * attr,char * buf)46 static ssize_t wm831x_unique_id_show(struct device *dev,
47 struct device_attribute *attr, char *buf)
48 {
49 struct wm831x *wm831x = dev_get_drvdata(dev);
50 int i, rval;
51 char id[WM831X_UNIQUE_ID_LEN];
52 ssize_t ret = 0;
53
54 rval = wm831x_unique_id_read(wm831x, id);
55 if (rval < 0)
56 return 0;
57
58 for (i = 0; i < WM831X_UNIQUE_ID_LEN; i++)
59 ret += sprintf(&buf[ret], "%02x", buf[i]);
60
61 ret += sprintf(&buf[ret], "\n");
62
63 return ret;
64 }
65
66 static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
67
wm831x_otp_init(struct wm831x * wm831x)68 int wm831x_otp_init(struct wm831x *wm831x)
69 {
70 char uuid[WM831X_UNIQUE_ID_LEN];
71 int ret;
72
73 ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
74 if (ret != 0)
75 dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
76 ret);
77
78 ret = wm831x_unique_id_read(wm831x, uuid);
79 if (ret == 0)
80 add_device_randomness(uuid, sizeof(uuid));
81 else
82 dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
83
84 return ret;
85 }
86
wm831x_otp_exit(struct wm831x * wm831x)87 void wm831x_otp_exit(struct wm831x *wm831x)
88 {
89 device_remove_file(wm831x->dev, &dev_attr_unique_id);
90 }
91
92