1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Microchip / Atmel SHA204A (I2C) driver.
4  *
5  * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
6  */
7 
8 #include <linux/delay.h>
9 #include <linux/device.h>
10 #include <linux/err.h>
11 #include <linux/errno.h>
12 #include <linux/i2c.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/scatterlist.h>
17 #include <linux/slab.h>
18 #include <linux/workqueue.h>
19 #include "atmel-i2c.h"
20 
atmel_sha204a_rng_done(struct atmel_i2c_work_data * work_data,void * areq,int status)21 static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data,
22 				   void *areq, int status)
23 {
24 	struct atmel_i2c_client_priv *i2c_priv = work_data->ctx;
25 	struct hwrng *rng = areq;
26 
27 	if (status)
28 		dev_warn_ratelimited(&i2c_priv->client->dev,
29 				     "i2c transaction failed (%d)\n",
30 				     status);
31 
32 	rng->priv = (unsigned long)work_data;
33 	atomic_dec(&i2c_priv->tfm_count);
34 }
35 
atmel_sha204a_rng_read_nonblocking(struct hwrng * rng,void * data,size_t max)36 static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data,
37 					      size_t max)
38 {
39 	struct atmel_i2c_client_priv *i2c_priv;
40 	struct atmel_i2c_work_data *work_data;
41 
42 	i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng);
43 
44 	/* keep maximum 1 asynchronous read in flight at any time */
45 	if (!atomic_add_unless(&i2c_priv->tfm_count, 1, 1))
46 		return 0;
47 
48 	if (rng->priv) {
49 		work_data = (struct atmel_i2c_work_data *)rng->priv;
50 		max = min(sizeof(work_data->cmd.data), max);
51 		memcpy(data, &work_data->cmd.data, max);
52 		rng->priv = 0;
53 	} else {
54 		work_data = kmalloc(sizeof(*work_data), GFP_ATOMIC);
55 		if (!work_data)
56 			return -ENOMEM;
57 
58 		work_data->ctx = i2c_priv;
59 		work_data->client = i2c_priv->client;
60 
61 		max = 0;
62 	}
63 
64 	atmel_i2c_init_random_cmd(&work_data->cmd);
65 	atmel_i2c_enqueue(work_data, atmel_sha204a_rng_done, rng);
66 
67 	return max;
68 }
69 
atmel_sha204a_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)70 static int atmel_sha204a_rng_read(struct hwrng *rng, void *data, size_t max,
71 				  bool wait)
72 {
73 	struct atmel_i2c_client_priv *i2c_priv;
74 	struct atmel_i2c_cmd cmd;
75 	int ret;
76 
77 	if (!wait)
78 		return atmel_sha204a_rng_read_nonblocking(rng, data, max);
79 
80 	i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng);
81 
82 	atmel_i2c_init_random_cmd(&cmd);
83 
84 	ret = atmel_i2c_send_receive(i2c_priv->client, &cmd);
85 	if (ret)
86 		return ret;
87 
88 	max = min(sizeof(cmd.data), max);
89 	memcpy(data, cmd.data, max);
90 
91 	return max;
92 }
93 
atmel_sha204a_otp_read(struct i2c_client * client,u16 addr,u8 * otp)94 static int atmel_sha204a_otp_read(struct i2c_client *client, u16 addr, u8 *otp)
95 {
96 	struct atmel_i2c_cmd cmd;
97 	int ret = -1;
98 
99 	if (atmel_i2c_init_read_otp_cmd(&cmd, addr) < 0) {
100 		dev_err(&client->dev, "failed, invalid otp address %04X\n",
101 			addr);
102 		return ret;
103 	}
104 
105 	ret = atmel_i2c_send_receive(client, &cmd);
106 
107 	if (cmd.data[0] == 0xff) {
108 		dev_err(&client->dev, "failed, device not ready\n");
109 		return -EINVAL;
110 	}
111 
112 	memcpy(otp, cmd.data+1, 4);
113 
114 	return ret;
115 }
116 
otp_show(struct device * dev,struct device_attribute * attr,char * buf)117 static ssize_t otp_show(struct device *dev,
118 			struct device_attribute *attr, char *buf)
119 {
120 	u16 addr;
121 	u8 otp[OTP_ZONE_SIZE];
122 	char *str = buf;
123 	struct i2c_client *client = to_i2c_client(dev);
124 	int i;
125 
126 	for (addr = 0; addr < OTP_ZONE_SIZE/4; addr++) {
127 		if (atmel_sha204a_otp_read(client, addr, otp + addr * 4) < 0) {
128 			dev_err(dev, "failed to read otp zone\n");
129 			break;
130 		}
131 	}
132 
133 	for (i = 0; i < addr*2; i++)
134 		str += sprintf(str, "%02X", otp[i]);
135 	str += sprintf(str, "\n");
136 	return str - buf;
137 }
138 static DEVICE_ATTR_RO(otp);
139 
140 static struct attribute *atmel_sha204a_attrs[] = {
141 	&dev_attr_otp.attr,
142 	NULL
143 };
144 
145 static const struct attribute_group atmel_sha204a_groups = {
146 	.name = "atsha204a",
147 	.attrs = atmel_sha204a_attrs,
148 };
149 
atmel_sha204a_probe(struct i2c_client * client)150 static int atmel_sha204a_probe(struct i2c_client *client)
151 {
152 	struct atmel_i2c_client_priv *i2c_priv;
153 	int ret;
154 
155 	ret = atmel_i2c_probe(client);
156 	if (ret)
157 		return ret;
158 
159 	i2c_priv = i2c_get_clientdata(client);
160 
161 	memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng));
162 
163 	i2c_priv->hwrng.name = dev_name(&client->dev);
164 	i2c_priv->hwrng.read = atmel_sha204a_rng_read;
165 
166 	ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng);
167 	if (ret)
168 		dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);
169 
170 	/* otp read out */
171 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
172 		return -ENODEV;
173 
174 	ret = sysfs_create_group(&client->dev.kobj, &atmel_sha204a_groups);
175 	if (ret) {
176 		dev_err(&client->dev, "failed to register sysfs entry\n");
177 		return ret;
178 	}
179 
180 	return ret;
181 }
182 
atmel_sha204a_remove(struct i2c_client * client)183 static void atmel_sha204a_remove(struct i2c_client *client)
184 {
185 	struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
186 
187 	if (atomic_read(&i2c_priv->tfm_count)) {
188 		dev_emerg(&client->dev, "Device is busy, will remove it anyhow\n");
189 		return;
190 	}
191 
192 	sysfs_remove_group(&client->dev.kobj, &atmel_sha204a_groups);
193 
194 	kfree((void *)i2c_priv->hwrng.priv);
195 }
196 
197 static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = {
198 	{ .compatible = "atmel,atsha204", },
199 	{ .compatible = "atmel,atsha204a", },
200 	{ /* sentinel */ }
201 };
202 MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
203 
204 static const struct i2c_device_id atmel_sha204a_id[] = {
205 	{ "atsha204", 0 },
206 	{ "atsha204a", 0 },
207 	{ /* sentinel */ }
208 };
209 MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
210 
211 static struct i2c_driver atmel_sha204a_driver = {
212 	.probe			= atmel_sha204a_probe,
213 	.remove			= atmel_sha204a_remove,
214 	.id_table		= atmel_sha204a_id,
215 
216 	.driver.name		= "atmel-sha204a",
217 	.driver.of_match_table	= of_match_ptr(atmel_sha204a_dt_ids),
218 };
219 
atmel_sha204a_init(void)220 static int __init atmel_sha204a_init(void)
221 {
222 	return i2c_add_driver(&atmel_sha204a_driver);
223 }
224 
atmel_sha204a_exit(void)225 static void __exit atmel_sha204a_exit(void)
226 {
227 	atmel_i2c_flush_queue();
228 	i2c_del_driver(&atmel_sha204a_driver);
229 }
230 
231 module_init(atmel_sha204a_init);
232 module_exit(atmel_sha204a_exit);
233 
234 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
235 MODULE_DESCRIPTION("Microchip / Atmel SHA204A (I2C) driver");
236 MODULE_LICENSE("GPL v2");
237