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_probe(struct i2c_client * client)94 static int atmel_sha204a_probe(struct i2c_client *client)
95 {
96 struct atmel_i2c_client_priv *i2c_priv;
97 int ret;
98
99 ret = atmel_i2c_probe(client);
100 if (ret)
101 return ret;
102
103 i2c_priv = i2c_get_clientdata(client);
104
105 memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng));
106
107 i2c_priv->hwrng.name = dev_name(&client->dev);
108 i2c_priv->hwrng.read = atmel_sha204a_rng_read;
109
110 ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng);
111 if (ret)
112 dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);
113
114 return ret;
115 }
116
atmel_sha204a_remove(struct i2c_client * client)117 static void atmel_sha204a_remove(struct i2c_client *client)
118 {
119 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
120
121 if (atomic_read(&i2c_priv->tfm_count)) {
122 dev_emerg(&client->dev, "Device is busy, will remove it anyhow\n");
123 return;
124 }
125
126 kfree((void *)i2c_priv->hwrng.priv);
127 }
128
129 static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = {
130 { .compatible = "atmel,atsha204", },
131 { .compatible = "atmel,atsha204a", },
132 { /* sentinel */ }
133 };
134 MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
135
136 static const struct i2c_device_id atmel_sha204a_id[] = {
137 { "atsha204", 0 },
138 { "atsha204a", 0 },
139 { /* sentinel */ }
140 };
141 MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
142
143 static struct i2c_driver atmel_sha204a_driver = {
144 .probe = atmel_sha204a_probe,
145 .remove = atmel_sha204a_remove,
146 .id_table = atmel_sha204a_id,
147
148 .driver.name = "atmel-sha204a",
149 .driver.of_match_table = of_match_ptr(atmel_sha204a_dt_ids),
150 };
151
atmel_sha204a_init(void)152 static int __init atmel_sha204a_init(void)
153 {
154 return i2c_add_driver(&atmel_sha204a_driver);
155 }
156
atmel_sha204a_exit(void)157 static void __exit atmel_sha204a_exit(void)
158 {
159 atmel_i2c_flush_queue();
160 i2c_del_driver(&atmel_sha204a_driver);
161 }
162
163 module_init(atmel_sha204a_init);
164 module_exit(atmel_sha204a_exit);
165
166 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
167 MODULE_LICENSE("GPL v2");
168