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 { 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 } 116 117 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 }; 151 152 static int __init atmel_sha204a_init(void) 153 { 154 return i2c_add_driver(&atmel_sha204a_driver); 155 } 156 157 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