crypto: atmel-ecc - factor out code that can be shared

In preparation of adding support for the random number generator in
Atmel atsha204a devices, refactor the existing atmel-ecc driver (which
drives hardware that is closely related) so we can share the basic
I2C and command queuing routines.
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

@@ -519,9 +519,13 @@ config CRYPTO_DEV_ATMEL_SHA
 	  To compile this driver as a module, choose M here: the module
 	  will be called atmel-sha.
 
+config CRYPTO_DEV_ATMEL_I2C
+	tristate
+
 config CRYPTO_DEV_ATMEL_ECC
 	tristate "Support for Microchip / Atmel ECC hw accelerator"
 	depends on I2C
+	select CRYPTO_DEV_ATMEL_I2C
 	select CRYPTO_ECDH
 	select CRC16
 	help

drivers/crypto/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_AES) += atmel-aes.o
 obj-$(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_CAVIUM_ZIP) += cavium/
 obj-$(CONFIG_CRYPTO_DEV_CCP) += ccp/

drivers/crypto/atmel-i2c.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Microchip / Atmel ECC (I2C) driver.
+ *
+ * Copyright (c) 2017, Microchip Technology Inc.
+ * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
+ */
+
+#include <linux/bitrev.h>
+#include <linux/crc16.h>
+#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"
+
+/**
+ * atmel_i2c_checksum() - Generate 16-bit CRC as required by ATMEL ECC.
+ * CRC16 verification of the count, opcode, param1, param2 and data bytes.
+ * The checksum is saved in little-endian format in the least significant
+ * two bytes of the command. CRC polynomial is 0x8005 and the initial register
+ * value should be zero.
+ *
+ * @cmd : structure used for communicating with the device.
+ */
+static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd)
+{
+	u8 *data = &cmd->count;
+	size_t len = cmd->count - CRC_SIZE;
+	u16 *__crc16 = (u16 *)(data + len);
+
+	*__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len)));
+}
+
+void atmel_i2c_init_read_cmd(struct atmel_i2c_cmd *cmd)
+{
+	cmd->word_addr = COMMAND;
+	cmd->opcode = OPCODE_READ;
+	/*
+	 * Read the word from Configuration zone that contains the lock bytes
+	 * (UserExtra, Selector, LockValue, LockConfig).
+	 */
+	cmd->param1 = CONFIG_ZONE;
+	cmd->param2 = DEVICE_LOCK_ADDR;
+	cmd->count = READ_COUNT;
+
+	atmel_i2c_checksum(cmd);
+
+	cmd->msecs = MAX_EXEC_TIME_READ;
+	cmd->rxsize = READ_RSP_SIZE;
+}
+EXPORT_SYMBOL(atmel_i2c_init_read_cmd);
+
+void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid)
+{
+	cmd->word_addr = COMMAND;
+	cmd->count = GENKEY_COUNT;
+	cmd->opcode = OPCODE_GENKEY;
+	cmd->param1 = GENKEY_MODE_PRIVATE;
+	/* a random private key will be generated and stored in slot keyID */
+	cmd->param2 = cpu_to_le16(keyid);
+
+	atmel_i2c_checksum(cmd);
+
+	cmd->msecs = MAX_EXEC_TIME_GENKEY;
+	cmd->rxsize = GENKEY_RSP_SIZE;
+}
+EXPORT_SYMBOL(atmel_i2c_init_genkey_cmd);
+
+int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
+			    struct scatterlist *pubkey)
+{
+	size_t copied;
+
+	cmd->word_addr = COMMAND;
+	cmd->count = ECDH_COUNT;
+	cmd->opcode = OPCODE_ECDH;
+	cmd->param1 = ECDH_PREFIX_MODE;
+	/* private key slot */
+	cmd->param2 = cpu_to_le16(DATA_SLOT_2);
+
+	/*
+	 * The device only supports NIST P256 ECC keys. The public key size will
+	 * always be the same. Use a macro for the key size to avoid unnecessary
+	 * computations.
+	 */
+	copied = sg_copy_to_buffer(pubkey,
+				   sg_nents_for_len(pubkey,
+						    ATMEL_ECC_PUBKEY_SIZE),
+				   cmd->data, ATMEL_ECC_PUBKEY_SIZE);
+	if (copied != ATMEL_ECC_PUBKEY_SIZE)
+		return -EINVAL;
+
+	atmel_i2c_checksum(cmd);
+
+	cmd->msecs = MAX_EXEC_TIME_ECDH;
+	cmd->rxsize = ECDH_RSP_SIZE;
+
+	return 0;
+}
+EXPORT_SYMBOL(atmel_i2c_init_ecdh_cmd);
+
+/*
+ * After wake and after execution of a command, there will be error, status, or
+ * result bytes in the device's output register that can be retrieved by the
+ * system. When the length of that group is four bytes, the codes returned are
+ * detailed in error_list.
+ */
+static int atmel_i2c_status(struct device *dev, u8 *status)
+{
+	size_t err_list_len = ARRAY_SIZE(error_list);
+	int i;
+	u8 err_id = status[1];
+
+	if (*status != STATUS_SIZE)
+		return 0;
+
+	if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR)
+		return 0;
+
+	for (i = 0; i < err_list_len; i++)
+		if (error_list[i].value == err_id)
+			break;
+
+	/* if err_id is not in the error_list then ignore it */
+	if (i != err_list_len) {
+		dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text);
+		return err_id;
+	}
+
+	return 0;
+}
+
+static int atmel_i2c_wakeup(struct i2c_client *client)
+{
+	struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
+	u8 status[STATUS_RSP_SIZE];
+	int ret;
+
+	/*
+	 * The device ignores any levels or transitions on the SCL pin when the
+	 * device is idle, asleep or during waking up. Don't check for error
+	 * when waking up the device.
+	 */
+	i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
+
+	/*
+	 * Wait to wake the device. Typical execution times for ecdh and genkey
+	 * are around tens of milliseconds. Delta is chosen to 50 microseconds.
+	 */
+	usleep_range(TWHI_MIN, TWHI_MAX);
+
+	ret = i2c_master_recv(client, status, STATUS_SIZE);
+	if (ret < 0)
+		return ret;
+
+	return atmel_i2c_status(&client->dev, status);
+}
+
+static int atmel_i2c_sleep(struct i2c_client *client)
+{
+	u8 sleep = SLEEP_TOKEN;
+
+	return i2c_master_send(client, &sleep, 1);
+}
+
+/*
+ * atmel_i2c_send_receive() - send a command to the device and receive its
+ *                            response.
+ * @client: i2c client device
+ * @cmd   : structure used to communicate with the device
+ *
+ * After the device receives a Wake token, a watchdog counter starts within the
+ * device. After the watchdog timer expires, the device enters sleep mode
+ * regardless of whether some I/O transmission or command execution is in
+ * progress. If a command is attempted when insufficient time remains prior to
+ * watchdog timer execution, the device will return the watchdog timeout error
+ * code without attempting to execute the command. There is no way to reset the
+ * counter other than to put the device into sleep or idle mode and then
+ * wake it up again.
+ */
+int atmel_i2c_send_receive(struct i2c_client *client, struct atmel_i2c_cmd *cmd)
+{
+	struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
+	int ret;
+
+	mutex_lock(&i2c_priv->lock);
+
+	ret = atmel_i2c_wakeup(client);
+	if (ret)
+		goto err;
+
+	/* send the command */
+	ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE);
+	if (ret < 0)
+		goto err;
+
+	/* delay the appropriate amount of time for command to execute */
+	msleep(cmd->msecs);
+
+	/* receive the response */
+	ret = i2c_master_recv(client, cmd->data, cmd->rxsize);
+	if (ret < 0)
+		goto err;
+
+	/* put the device into low-power mode */
+	ret = atmel_i2c_sleep(client);
+	if (ret < 0)
+		goto err;
+
+	mutex_unlock(&i2c_priv->lock);
+	return atmel_i2c_status(&client->dev, cmd->data);
+err:
+	mutex_unlock(&i2c_priv->lock);
+	return ret;
+}
+EXPORT_SYMBOL(atmel_i2c_send_receive);
+
+static void atmel_i2c_work_handler(struct work_struct *work)
+{
+	struct atmel_i2c_work_data *work_data =
+			container_of(work, struct atmel_i2c_work_data, work);
+	struct atmel_i2c_cmd *cmd = &work_data->cmd;
+	struct i2c_client *client = work_data->client;
+	int status;
+
+	status = atmel_i2c_send_receive(client, cmd);
+	work_data->cbk(work_data, work_data->areq, status);
+}
+
+void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
+		       void (*cbk)(struct atmel_i2c_work_data *work_data,
+				   void *areq, int status),
+		       void *areq)
+{
+	work_data->cbk = (void *)cbk;
+	work_data->areq = areq;
+
+	INIT_WORK(&work_data->work, atmel_i2c_work_handler);
+	schedule_work(&work_data->work);
+}
+EXPORT_SYMBOL(atmel_i2c_enqueue);
+
+static inline size_t atmel_i2c_wake_token_sz(u32 bus_clk_rate)
+{
+	u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC);
+
+	/* return the size of the wake_token in bytes */
+	return DIV_ROUND_UP(no_of_bits, 8);
+}
+
+static int device_sanity_check(struct i2c_client *client)
+{
+	struct atmel_i2c_cmd *cmd;
+	int ret;
+
+	cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
+	if (!cmd)
+		return -ENOMEM;
+
+	atmel_i2c_init_read_cmd(cmd);
+
+	ret = atmel_i2c_send_receive(client, cmd);
+	if (ret)
+		goto free_cmd;
+
+	/*
+	 * It is vital that the Configuration, Data and OTP zones be locked
+	 * prior to release into the field of the system containing the device.
+	 * Failure to lock these zones may permit modification of any secret
+	 * keys and may lead to other security problems.
+	 */
+	if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) {
+		dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n");
+		ret = -ENOTSUPP;
+	}
+
+	/* fall through */
+free_cmd:
+	kfree(cmd);
+	return ret;
+}
+
+int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	struct atmel_i2c_client_priv *i2c_priv;
+	struct device *dev = &client->dev;
+	int ret;
+	u32 bus_clk_rate;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		dev_err(dev, "I2C_FUNC_I2C not supported\n");
+		return -ENODEV;
+	}
+
+	bus_clk_rate = i2c_acpi_find_bus_speed(&client->adapter->dev);
+	if (!bus_clk_rate) {
+		ret = device_property_read_u32(&client->adapter->dev,
+					       "clock-frequency", &bus_clk_rate);
+		if (ret) {
+			dev_err(dev, "failed to read clock-frequency property\n");
+			return ret;
+		}
+	}
+
+	if (bus_clk_rate > 1000000L) {
+		dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n",
+			bus_clk_rate);
+		return -EINVAL;
+	}
+
+	i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL);
+	if (!i2c_priv)
+		return -ENOMEM;
+
+	i2c_priv->client = client;
+	mutex_init(&i2c_priv->lock);
+
+	/*
+	 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate -
+	 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz
+	 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE.
+	 */
+	i2c_priv->wake_token_sz = atmel_i2c_wake_token_sz(bus_clk_rate);
+
+	memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token));
+
+	atomic_set(&i2c_priv->tfm_count, 0);
+
+	i2c_set_clientdata(client, i2c_priv);
+
+	ret = device_sanity_check(client);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(atmel_i2c_probe);
+
+MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
+MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
+MODULE_LICENSE("GPL v2");

drivers/crypto/atmel-ecc.h → drivers/crypto/atmel-i2c.h

@@ -4,8 +4,8 @@
  * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
  */
 
-#ifndef __ATMEL_ECC_H__
-#define __ATMEL_ECC_H__
+#ifndef __ATMEL_I2C_H__
+#define __ATMEL_I2C_H__
 
 #define ATMEL_ECC_PRIORITY		300
 
@@ -31,7 +31,7 @@
 #define MAX_RSP_SIZE			GENKEY_RSP_SIZE
 
 /**
- * atmel_ecc_cmd - structure used for communicating with the device.
+ * atmel_i2c_cmd - structure used for communicating with the device.
  * @word_addr: indicates the function of the packet sent to the device. This
  *             byte should have a value of COMMAND for normal operation.
  * @count    : number of bytes to be transferred to (or from) the device.
@@ -42,7 +42,7 @@
  * @rxsize   : size of the data received from i2c client.
  * @msecs    : command execution time in milliseconds
  */
-struct atmel_ecc_cmd {
+struct atmel_i2c_cmd {
 	u8 word_addr;
 	u8 count;
 	u8 opcode;
@@ -113,4 +113,74 @@ static const struct {
 #define ECDH_COUNT			71
 #define ECDH_PREFIX_MODE		0x00
 
-#endif /* __ATMEL_ECC_H__ */
+/* Used for binding tfm objects to i2c clients. */
+struct atmel_ecc_driver_data {
+	struct list_head i2c_client_list;
+	spinlock_t i2c_list_lock;
+} ____cacheline_aligned;
+
+/**
+ * atmel_i2c_client_priv - i2c_client private data
+ * @client              : pointer to i2c client device
+ * @i2c_client_list_node: part of i2c_client_list
+ * @lock                : lock for sending i2c commands
+ * @wake_token          : wake token array of zeros
+ * @wake_token_sz       : size in bytes of the wake_token
+ * @tfm_count           : number of active crypto transformations on i2c client
+ *
+ * Reads and writes from/to the i2c client are sequential. The first byte
+ * transmitted to the device is treated as the byte size. Any attempt to send
+ * more than this number of bytes will cause the device to not ACK those bytes.
+ * After the host writes a single command byte to the input buffer, reads are
+ * prohibited until after the device completes command execution. Use a mutex
+ * when sending i2c commands.
+ */
+struct atmel_i2c_client_priv {
+	struct i2c_client *client;
+	struct list_head i2c_client_list_node;
+	struct mutex lock;
+	u8 wake_token[WAKE_TOKEN_MAX_SIZE];
+	size_t wake_token_sz;
+	atomic_t tfm_count ____cacheline_aligned;
+};
+
+/**
+ * atmel_i2c_work_data - data structure representing the work
+ * @ctx : transformation context.
+ * @cbk : pointer to a callback function to be invoked upon completion of this
+ *        request. This has the form:
+ *        callback(struct atmel_i2c_work_data *work_data, void *areq, u8 status)
+ *        where:
+ *        @work_data: data structure representing the work
+ *        @areq     : optional pointer to an argument passed with the original
+ *                    request.
+ *        @status   : status returned from the i2c client device or i2c error.
+ * @areq: optional pointer to a user argument for use at callback time.
+ * @work: describes the task to be executed.
+ * @cmd : structure used for communicating with the device.
+ */
+struct atmel_i2c_work_data {
+	void *ctx;
+	struct i2c_client *client;
+	void (*cbk)(struct atmel_i2c_work_data *work_data, void *areq,
+		    int status);
+	void *areq;
+	struct work_struct work;
+	struct atmel_i2c_cmd cmd;
+};
+
+int atmel_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id);
+
+void atmel_i2c_enqueue(struct atmel_i2c_work_data *work_data,
+		       void (*cbk)(struct atmel_i2c_work_data *work_data,
+				   void *areq, int status),
+		       void *areq);
+
+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_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid);
+int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
+			    struct scatterlist *pubkey);
+
+#endif /* __ATMEL_I2C_H__ */