crypto: atmel-i2c - add support for SHA204A random number generator
authorArd Biesheuvel <ard.biesheuvel@linaro.org>
Fri, 24 May 2019 16:26:49 +0000 (18:26 +0200)
committerHerbert Xu <herbert@gondor.apana.org.au>
Thu, 30 May 2019 07:35:45 +0000 (15:35 +0800)
The Linaro/96boards Secure96 mezzanine contains (among other things)
an Atmel SHA204A symmetric crypto processor. This chip implements a
number of different functionalities, but one that is highly useful
for many different 96boards platforms is the random number generator.

So let's implement a driver for the SHA204A, and for the time being,
implement support for the random number generator only.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
drivers/crypto/Kconfig
drivers/crypto/Makefile
drivers/crypto/atmel-i2c.c
drivers/crypto/atmel-i2c.h
drivers/crypto/atmel-sha204a.c [new file with mode: 0644]

index 20674842261e98b70db3836cf76006b25b0119e1..bc7abad9fdff03c5463c17e5d97dd2091379c810 100644 (file)
@@ -536,6 +536,20 @@ config CRYPTO_DEV_ATMEL_ECC
          To compile this driver as a module, choose M here: the module
          will be called atmel-ecc.
 
+config CRYPTO_DEV_ATMEL_SHA204A
+       tristate "Support for Microchip / Atmel SHA accelerator and RNG"
+       depends on I2C
+       select CRYPTO_DEV_ATMEL_I2C
+       select HW_RANDOM
+       help
+         Microhip / Atmel SHA accelerator and RNG.
+         Select this if you want to use the Microchip / Atmel SHA204A
+         module as a random number generator. (Other functions of the
+         chip are currently not exposed by this driver)
+
+         To compile this driver as a module, choose M here: the module
+         will be called atmel-sha204a.
+
 config CRYPTO_DEV_CCP
        bool "Support for AMD Secure Processor"
        depends on ((X86 && PCI) || (ARM64 && (OF_ADDRESS || ACPI))) && HAS_IOMEM
index 394e840899244fde05b0fe24e413672eeac8b6cc..afc4753b5d287207e8508cb2cfbfe3a88542d2c8 100644 (file)
@@ -4,6 +4,7 @@ obj-$(CONFIG_CRYPTO_DEV_ATMEL_SHA) += atmel-sha.o
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_TDES) += atmel-tdes.o
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_I2C) += atmel-i2c.o
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_ECC) += atmel-ecc.o
+obj-$(CONFIG_CRYPTO_DEV_ATMEL_SHA204A) += atmel-sha204a.o
 obj-$(CONFIG_CRYPTO_DEV_CAVIUM_ZIP) += cavium/
 obj-$(CONFIG_CRYPTO_DEV_CCP) += ccp/
 obj-$(CONFIG_CRYPTO_DEV_CCREE) += ccree/
index 5e099368d120fdf658f30351af9fca51ed582940..be49ab7f43380e408856779f5aa08b6808ea53da 100644 (file)
@@ -58,6 +58,21 @@ void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd)
 }
 EXPORT_SYMBOL(atmel_i2c_init_read_cmd);
 
+void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd)
+{
+       cmd->word_addr = COMMAND;
+       cmd->opcode = OPCODE_RANDOM;
+       cmd->param1 = 0;
+       cmd->param2 = 0;
+       cmd->count = RANDOM_COUNT;
+
+       atmel_i2c_checksum(cmd);
+
+       cmd->msecs = MAX_EXEC_TIME_RANDOM;
+       cmd->rxsize = RANDOM_RSP_SIZE;
+}
+EXPORT_SYMBOL(atmel_i2c_init_random_cmd);
+
 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid)
 {
        cmd->word_addr = COMMAND;
index 82de5166acfa0836acf6d73aa3ce03f43b46a71d..c6bd43b78f33c135a26b71b39e0193fd5f93bf99 100644 (file)
@@ -7,6 +7,8 @@
 #ifndef __ATMEL_I2C_H__
 #define __ATMEL_I2C_H__
 
+#include <linux/hw_random.h>
+
 #define ATMEL_ECC_PRIORITY             300
 
 #define COMMAND                                0x03 /* packet function */
@@ -28,6 +30,7 @@
 #define GENKEY_RSP_SIZE                        (ATMEL_ECC_PUBKEY_SIZE + \
                                         CMD_OVERHEAD_SIZE)
 #define READ_RSP_SIZE                  (4 + CMD_OVERHEAD_SIZE)
+#define RANDOM_RSP_SIZE                        (32 + CMD_OVERHEAD_SIZE)
 #define MAX_RSP_SIZE                   GENKEY_RSP_SIZE
 
 /**
@@ -96,15 +99,20 @@ static const struct {
 #define MAX_EXEC_TIME_ECDH             58
 #define MAX_EXEC_TIME_GENKEY           115
 #define MAX_EXEC_TIME_READ             1
+#define MAX_EXEC_TIME_RANDOM           50
 
 /* Command opcode */
 #define OPCODE_ECDH                    0x43
 #define OPCODE_GENKEY                  0x40
 #define OPCODE_READ                    0x02
+#define OPCODE_RANDOM                  0x1b
 
 /* Definitions for the READ Command */
 #define READ_COUNT                     7
 
+/* Definitions for the RANDOM Command */
+#define RANDOM_COUNT                   7
+
 /* Definitions for the GenKey Command */
 #define GENKEY_COUNT                   7
 #define GENKEY_MODE_PRIVATE            0x04
@@ -142,6 +150,7 @@ struct atmel_i2c_client_priv {
        u8 wake_token[WAKE_TOKEN_MAX_SIZE];
        size_t wake_token_sz;
        atomic_t tfm_count ____cacheline_aligned;
+       struct hwrng hwrng;
 };
 
 /**
@@ -179,6 +188,7 @@ void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
 int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd);
 
 void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd);
+void atmel_i2c_init_random_cmd(struct atmel_i2c_cmd *cmd);
 void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid);
 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
                            struct scatterlist *pubkey);
diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c
new file mode 100644 (file)
index 0000000..ea0d206
--- /dev/null
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Microchip / Atmel SHA204A (I2C) driver.
+ *
+ * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include "atmel-i2c.h"
+
+static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data,
+                                  void *areq, int status)
+{
+       struct atmel_i2c_client_priv *i2c_priv = work_data->ctx;
+       struct hwrng *rng = areq;
+
+       if (status)
+               dev_warn_ratelimited(&i2c_priv->client->dev,
+                                    "i2c transaction failed (%d)\n",
+                                    status);
+
+       rng->priv = (unsigned long)work_data;
+       atomic_dec(&i2c_priv->tfm_count);
+}
+
+static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data,
+                                             size_t max)
+{
+       struct atmel_i2c_client_priv *i2c_priv;
+       struct atmel_i2c_work_data *work_data;
+
+       i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng);
+
+       /* keep maximum 1 asynchronous read in flight at any time */
+       if (!atomic_add_unless(&i2c_priv->tfm_count, 1, 1))
+               return 0;
+
+       if (rng->priv) {
+               work_data = (struct atmel_i2c_work_data *)rng->priv;
+               max = min(sizeof(work_data->cmd.data), max);
+               memcpy(data, &work_data->cmd.data, max);
+               rng->priv = 0;
+       } else {
+               work_data = kmalloc(sizeof(*work_data), GFP_ATOMIC);
+               if (!work_data)
+                       return -ENOMEM;
+
+               work_data->ctx = i2c_priv;
+               work_data->client = i2c_priv->client;
+
+               max = 0;
+       }
+
+       atmel_i2c_init_random_cmd(&work_data->cmd);
+       atmel_i2c_enqueue(work_data, atmel_sha204a_rng_done, rng);
+
+       return max;
+}
+
+static int atmel_sha204a_rng_read(struct hwrng *rng, void *data, size_t max,
+                                 bool wait)
+{
+       struct atmel_i2c_client_priv *i2c_priv;
+       struct atmel_i2c_cmd cmd;
+       int ret;
+
+       if (!wait)
+               return atmel_sha204a_rng_read_nonblocking(rng, data, max);
+
+       i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng);
+
+       atmel_i2c_init_random_cmd(&cmd);
+
+       ret = atmel_i2c_send_receive(i2c_priv->client, &cmd);
+       if (ret)
+               return ret;
+
+       max = min(sizeof(cmd.data), max);
+       memcpy(data, cmd.data, max);
+
+       return max;
+}
+
+static int atmel_sha204a_probe(struct i2c_client *client,
+                              const struct i2c_device_id *id)
+{
+       struct atmel_i2c_client_priv *i2c_priv;
+       int ret;
+
+       ret = atmel_i2c_probe(client, id);
+       if (ret)
+               return ret;
+
+       i2c_priv = i2c_get_clientdata(client);
+
+       memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng));
+
+       i2c_priv->hwrng.name = dev_name(&client->dev);
+       i2c_priv->hwrng.read = atmel_sha204a_rng_read;
+       i2c_priv->hwrng.quality = 1024;
+
+       ret = hwrng_register(&i2c_priv->hwrng);
+       if (ret)
+               dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);
+
+       return ret;
+}
+
+static int atmel_sha204a_remove(struct i2c_client *client)
+{
+       struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
+
+       if (atomic_read(&i2c_priv->tfm_count)) {
+               dev_err(&client->dev, "Device is busy\n");
+               return -EBUSY;
+       }
+
+       if (i2c_priv->hwrng.priv)
+               kfree((void *)i2c_priv->hwrng.priv);
+       hwrng_unregister(&i2c_priv->hwrng);
+
+       return 0;
+}
+
+static const struct of_device_id atmel_sha204a_dt_ids[] = {
+       { .compatible = "atmel,atsha204a", },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids);
+
+static const struct i2c_device_id atmel_sha204a_id[] = {
+       { "atsha204a", 0 },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id);
+
+static struct i2c_driver atmel_sha204a_driver = {
+       .probe                  = atmel_sha204a_probe,
+       .remove                 = atmel_sha204a_remove,
+       .id_table               = atmel_sha204a_id,
+
+       .driver.name            = "atmel-sha204a",
+       .driver.of_match_table  = of_match_ptr(atmel_sha204a_dt_ids),
+};
+
+static int __init atmel_sha204a_init(void)
+{
+       return i2c_add_driver(&atmel_sha204a_driver);
+}
+
+static void __exit atmel_sha204a_exit(void)
+{
+       flush_scheduled_work();
+       i2c_del_driver(&atmel_sha204a_driver);
+}
+
+module_init(atmel_sha204a_init);
+module_exit(atmel_sha204a_exit);
+
+MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
+MODULE_LICENSE("GPL v2");