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
21static 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
36static 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
70static 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
94static 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
117static 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
129static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = {
130	{ .compatible = "atmel,atsha204", },
131	{ .compatible = "atmel,atsha204a", },
132	{ /* sentinel */ }
133};
134MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
135
136static const struct i2c_device_id atmel_sha204a_id[] = {
137	{ "atsha204", 0 },
138	{ "atsha204a", 0 },
139	{ /* sentinel */ }
140};
141MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
142
143static 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
152static int __init atmel_sha204a_init(void)
153{
154	return i2c_add_driver(&atmel_sha204a_driver);
155}
156
157static void __exit atmel_sha204a_exit(void)
158{
159	atmel_i2c_flush_queue();
160	i2c_del_driver(&atmel_sha204a_driver);
161}
162
163module_init(atmel_sha204a_init);
164module_exit(atmel_sha204a_exit);
165
166MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
167MODULE_LICENSE("GPL v2");
168