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_otp_read(struct i2c_client *client, u16 addr, u8 *otp) 95 { 96 struct atmel_i2c_cmd cmd; 97 int ret = -1; 98 99 if (atmel_i2c_init_read_otp_cmd(&cmd, addr) < 0) { 100 dev_err(&client->dev, "failed, invalid otp address %04X\n", 101 addr); 102 return ret; 103 } 104 105 ret = atmel_i2c_send_receive(client, &cmd); 106 107 if (cmd.data[0] == 0xff) { 108 dev_err(&client->dev, "failed, device not ready\n"); 109 return -EINVAL; 110 } 111 112 memcpy(otp, cmd.data+1, 4); 113 114 return ret; 115 } 116 117 static ssize_t otp_show(struct device *dev, 118 struct device_attribute *attr, char *buf) 119 { 120 u16 addr; 121 u8 otp[OTP_ZONE_SIZE]; 122 char *str = buf; 123 struct i2c_client *client = to_i2c_client(dev); 124 int i; 125 126 for (addr = 0; addr < OTP_ZONE_SIZE/4; addr++) { 127 if (atmel_sha204a_otp_read(client, addr, otp + addr * 4) < 0) { 128 dev_err(dev, "failed to read otp zone\n"); 129 break; 130 } 131 } 132 133 for (i = 0; i < addr*2; i++) 134 str += sprintf(str, "%02X", otp[i]); 135 str += sprintf(str, "\n"); 136 return str - buf; 137 } 138 static DEVICE_ATTR_RO(otp); 139 140 static struct attribute *atmel_sha204a_attrs[] = { 141 &dev_attr_otp.attr, 142 NULL 143 }; 144 145 static const struct attribute_group atmel_sha204a_groups = { 146 .name = "atsha204a", 147 .attrs = atmel_sha204a_attrs, 148 }; 149 150 static int atmel_sha204a_probe(struct i2c_client *client) 151 { 152 struct atmel_i2c_client_priv *i2c_priv; 153 int ret; 154 155 ret = atmel_i2c_probe(client); 156 if (ret) 157 return ret; 158 159 i2c_priv = i2c_get_clientdata(client); 160 161 memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng)); 162 163 i2c_priv->hwrng.name = dev_name(&client->dev); 164 i2c_priv->hwrng.read = atmel_sha204a_rng_read; 165 166 /* 167 * According to review by Bill Cox [1], this HWRNG has very low entropy. 168 * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html 169 */ 170 i2c_priv->hwrng.quality = 1; 171 172 ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); 173 if (ret) 174 dev_warn(&client->dev, "failed to register RNG (%d)\n", ret); 175 176 /* otp read out */ 177 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 178 return -ENODEV; 179 180 ret = sysfs_create_group(&client->dev.kobj, &atmel_sha204a_groups); 181 if (ret) { 182 dev_err(&client->dev, "failed to register sysfs entry\n"); 183 return ret; 184 } 185 186 return ret; 187 } 188 189 static void atmel_sha204a_remove(struct i2c_client *client) 190 { 191 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); 192 193 if (atomic_read(&i2c_priv->tfm_count)) { 194 dev_emerg(&client->dev, "Device is busy, will remove it anyhow\n"); 195 return; 196 } 197 198 sysfs_remove_group(&client->dev.kobj, &atmel_sha204a_groups); 199 200 kfree((void *)i2c_priv->hwrng.priv); 201 } 202 203 static const struct of_device_id atmel_sha204a_dt_ids[] __maybe_unused = { 204 { .compatible = "atmel,atsha204", }, 205 { .compatible = "atmel,atsha204a", }, 206 { /* sentinel */ } 207 }; 208 MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids); 209 210 static const struct i2c_device_id atmel_sha204a_id[] = { 211 { "atsha204" }, 212 { "atsha204a" }, 213 { /* sentinel */ } 214 }; 215 MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id); 216 217 static struct i2c_driver atmel_sha204a_driver = { 218 .probe = atmel_sha204a_probe, 219 .remove = atmel_sha204a_remove, 220 .id_table = atmel_sha204a_id, 221 222 .driver.name = "atmel-sha204a", 223 .driver.of_match_table = of_match_ptr(atmel_sha204a_dt_ids), 224 }; 225 226 static int __init atmel_sha204a_init(void) 227 { 228 return i2c_add_driver(&atmel_sha204a_driver); 229 } 230 231 static void __exit atmel_sha204a_exit(void) 232 { 233 atmel_i2c_flush_queue(); 234 i2c_del_driver(&atmel_sha204a_driver); 235 } 236 237 module_init(atmel_sha204a_init); 238 module_exit(atmel_sha204a_exit); 239 240 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>"); 241 MODULE_DESCRIPTION("Microchip / Atmel SHA204A (I2C) driver"); 242 MODULE_LICENSE("GPL v2"); 243