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 */ |
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 | |
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, fmt: "%*phN\n" , WM831X_UNIQUE_ID_LEN, id); |
53 | } |
54 | |
55 | static DEVICE_ATTR_RO(unique_id); |
56 | |
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(device: wm831x->dev, entry: &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, id: uuid); |
68 | if (ret == 0) |
69 | add_device_randomness(buf: uuid, len: sizeof(uuid)); |
70 | else |
71 | dev_err(wm831x->dev, "Failed to read UUID: %d\n" , ret); |
72 | |
73 | return ret; |
74 | } |
75 | |
76 | void wm831x_otp_exit(struct wm831x *wm831x) |
77 | { |
78 | device_remove_file(dev: wm831x->dev, attr: &dev_attr_unique_id); |
79 | } |
80 | |
81 | |