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			       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
119static 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_err(&client->dev, "Device is busy\n");
125		return -EBUSY;
126	}
127
128	if (i2c_priv->hwrng.priv)
129		kfree((void *)i2c_priv->hwrng.priv);
130
131	return 0;
132}
133
134static const struct of_device_id atmel_sha204a_dt_ids[] = {
135	{ .compatible = "atmel,atsha204a", },
136	{ /* sentinel */ }
137};
138MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
139
140static const struct i2c_device_id atmel_sha204a_id[] = {
141	{ "atsha204a", 0 },
142	{ /* sentinel */ }
143};
144MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
145
146static struct i2c_driver atmel_sha204a_driver = {
147	.probe			= atmel_sha204a_probe,
148	.remove			= atmel_sha204a_remove,
149	.id_table		= atmel_sha204a_id,
150
151	.driver.name		= "atmel-sha204a",
152	.driver.of_match_table	= of_match_ptr(atmel_sha204a_dt_ids),
153};
154
155static int __init atmel_sha204a_init(void)
156{
157	return i2c_add_driver(&atmel_sha204a_driver);
158}
159
160static void __exit atmel_sha204a_exit(void)
161{
162	flush_scheduled_work();
163	i2c_del_driver(&atmel_sha204a_driver);
164}
165
166module_init(atmel_sha204a_init);
167module_exit(atmel_sha204a_exit);
168
169MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
170MODULE_LICENSE("GPL v2");