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 
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 
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 
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 
94 static int atmel_sha204a_probe(struct i2c_client *client,
95 			       const struct i2c_device_id *id)
96 {
97 	struct atmel_i2c_client_priv *i2c_priv;
98 	int ret;
99 
100 	ret = atmel_i2c_probe(client, id);
101 	if (ret)
102 		return ret;
103 
104 	i2c_priv = i2c_get_clientdata(client);
105 
106 	memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng));
107 
108 	i2c_priv->hwrng.name = dev_name(&client->dev);
109 	i2c_priv->hwrng.read = atmel_sha204a_rng_read;
110 	i2c_priv->hwrng.quality = 1024;
111 
112 	ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng);
113 	if (ret)
114 		dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);
115 
116 	return ret;
117 }
118 
119 static int atmel_sha204a_remove(struct i2c_client *client)
120 {
121 	struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
122 
123 	if (atomic_read(&i2c_priv->tfm_count)) {
124 		dev_emerg(&client->dev, "Device is busy, will remove it anyhow\n");
125 		return 0;
126 	}
127 
128 	kfree((void *)i2c_priv->hwrng.priv);
129 
130 	return 0;
131 }
132 
133 static const struct of_device_id atmel_sha204a_dt_ids[] = {
134 	{ .compatible = "atmel,atsha204", },
135 	{ .compatible = "atmel,atsha204a", },
136 	{ /* sentinel */ }
137 };
138 MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
139 
140 static const struct i2c_device_id atmel_sha204a_id[] = {
141 	{ "atsha204", 0 },
142 	{ "atsha204a", 0 },
143 	{ /* sentinel */ }
144 };
145 MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
146 
147 static struct i2c_driver atmel_sha204a_driver = {
148 	.probe			= atmel_sha204a_probe,
149 	.remove			= atmel_sha204a_remove,
150 	.id_table		= atmel_sha204a_id,
151 
152 	.driver.name		= "atmel-sha204a",
153 	.driver.of_match_table	= of_match_ptr(atmel_sha204a_dt_ids),
154 };
155 
156 static int __init atmel_sha204a_init(void)
157 {
158 	return i2c_add_driver(&atmel_sha204a_driver);
159 }
160 
161 static void __exit atmel_sha204a_exit(void)
162 {
163 	atmel_i2c_flush_queue();
164 	i2c_del_driver(&atmel_sha204a_driver);
165 }
166 
167 module_init(atmel_sha204a_init);
168 module_exit(atmel_sha204a_exit);
169 
170 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
171 MODULE_LICENSE("GPL v2");
172