drivers/crypto/atmel-sha204a.c

   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_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
 134 static const struct of_device_id atmel_sha204a_dt_ids[] = {
 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         { "atsha204a", 0 },
 142         { /* sentinel */ }
 143 };
 144 MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
 145
 146 static 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
 155 static int __init atmel_sha204a_init(void)
 156 {
 157         return i2c_add_driver(&atmel_sha204a_driver);
 158 }
 159
 160 static void __exit atmel_sha204a_exit(void)
 161 {
 162         flush_scheduled_work();
 163         i2c_del_driver(&atmel_sha204a_driver);
 164 }
 165
 166 module_init(atmel_sha204a_init);
 167 module_exit(atmel_sha204a_exit);
 168
 169 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 170 MODULE_LICENSE("GPL v2");