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