drivers/staging/ccree/ssi_ivgen.c - arm/linux - Git at Google

 /*
  * Copyright (C) 2012-2017 ARM Limited or its affiliates.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */

 #include <linux/platform_device.h>
 #include <crypto/ctr.h>
 #include "ssi_config.h"
 #include "ssi_driver.h"
 #include "ssi_ivgen.h"
 #include "ssi_request_mgr.h"
 #include "ssi_sram_mgr.h"
 #include "ssi_buffer_mgr.h"

 /* The max. size of pool *MUST* be <= SRAM total size */
 #define SSI_IVPOOL_SIZE 1024
 /* The first 32B fraction of pool are dedicated to the
  * next encryption "key" & "IV" for pool regeneration
  */
 #define SSI_IVPOOL_META_SIZE (CC_AES_IV_SIZE + AES_KEYSIZE_128)
 #define SSI_IVPOOL_GEN_SEQ_LEN	4

 /**
  * struct ssi_ivgen_ctx -IV pool generation context
  * @pool:          the start address of the iv-pool resides in internal RAM
  * @ctr_key_dma:   address of pool's encryption key material in internal RAM
  * @ctr_iv_dma:    address of pool's counter iv in internal RAM
  * @next_iv_ofs:   the offset to the next available IV in pool
  * @pool_meta:     virt. address of the initial enc. key/IV
  * @pool_meta_dma: phys. address of the initial enc. key/IV
  */
 struct ssi_ivgen_ctx {
 	ssi_sram_addr_t pool;
 	ssi_sram_addr_t ctr_key;
 	ssi_sram_addr_t ctr_iv;
 	u32 next_iv_ofs;
 	u8 *pool_meta;
 	dma_addr_t pool_meta_dma;
 };

 /*!
  * Generates SSI_IVPOOL_SIZE of random bytes by
  * encrypting 0's using AES128-CTR.
  *
  * \param ivgen iv-pool context
  * \param iv_seq IN/OUT array to the descriptors sequence
  * \param iv_seq_len IN/OUT pointer to the sequence length
  */
 static int ssi_ivgen_generate_pool(
 	struct ssi_ivgen_ctx *ivgen_ctx,
 	struct cc_hw_desc iv_seq[],
 	unsigned int *iv_seq_len)
 {
 	unsigned int idx = *iv_seq_len;

 	if ((*iv_seq_len + SSI_IVPOOL_GEN_SEQ_LEN) > SSI_IVPOOL_SEQ_LEN) {
 		/* The sequence will be longer than allowed */
 		return -EINVAL;
 	}
 	/* Setup key */
 	hw_desc_init(&iv_seq[idx]);
 	set_din_sram(&iv_seq[idx], ivgen_ctx->ctr_key, AES_KEYSIZE_128);
 	set_setup_mode(&iv_seq[idx], SETUP_LOAD_KEY0);
 	set_cipher_config0(&iv_seq[idx], DESC_DIRECTION_ENCRYPT_ENCRYPT);
 	set_flow_mode(&iv_seq[idx], S_DIN_to_AES);
 	set_key_size_aes(&iv_seq[idx], CC_AES_128_BIT_KEY_SIZE);
 	set_cipher_mode(&iv_seq[idx], DRV_CIPHER_CTR);
 	idx++;

 	/* Setup cipher state */
 	hw_desc_init(&iv_seq[idx]);
 	set_din_sram(&iv_seq[idx], ivgen_ctx->ctr_iv, CC_AES_IV_SIZE);
 	set_cipher_config0(&iv_seq[idx], DESC_DIRECTION_ENCRYPT_ENCRYPT);
 	set_flow_mode(&iv_seq[idx], S_DIN_to_AES);
 	set_setup_mode(&iv_seq[idx], SETUP_LOAD_STATE1);
 	set_key_size_aes(&iv_seq[idx], CC_AES_128_BIT_KEY_SIZE);
 	set_cipher_mode(&iv_seq[idx], DRV_CIPHER_CTR);
 	idx++;

 	/* Perform dummy encrypt to skip first block */
 	hw_desc_init(&iv_seq[idx]);
 	set_din_const(&iv_seq[idx], 0, CC_AES_IV_SIZE);
 	set_dout_sram(&iv_seq[idx], ivgen_ctx->pool, CC_AES_IV_SIZE);
 	set_flow_mode(&iv_seq[idx], DIN_AES_DOUT);
 	idx++;

 	/* Generate IV pool */
 	hw_desc_init(&iv_seq[idx]);
 	set_din_const(&iv_seq[idx], 0, SSI_IVPOOL_SIZE);
 	set_dout_sram(&iv_seq[idx], ivgen_ctx->pool, SSI_IVPOOL_SIZE);
 	set_flow_mode(&iv_seq[idx], DIN_AES_DOUT);
 	idx++;

 	*iv_seq_len = idx; /* Update sequence length */

 	/* queue ordering assures pool readiness */
 	ivgen_ctx->next_iv_ofs = SSI_IVPOOL_META_SIZE;

 	return 0;
 }

 /*!
  * Generates the initial pool in SRAM.
  * This function should be invoked when resuming DX driver.
  *
  * \param drvdata
  *
  * \return int Zero for success, negative value otherwise.
  */
 int ssi_ivgen_init_sram_pool(struct ssi_drvdata *drvdata)
 {
 	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
 	struct cc_hw_desc iv_seq[SSI_IVPOOL_SEQ_LEN];
 	unsigned int iv_seq_len = 0;
 	int rc;

 	/* Generate initial enc. key/iv */
 	get_random_bytes(ivgen_ctx->pool_meta, SSI_IVPOOL_META_SIZE);

 	/* The first 32B reserved for the enc. Key/IV */
 	ivgen_ctx->ctr_key = ivgen_ctx->pool;
 	ivgen_ctx->ctr_iv = ivgen_ctx->pool + AES_KEYSIZE_128;

 	/* Copy initial enc. key and IV to SRAM at a single descriptor */
 	hw_desc_init(&iv_seq[iv_seq_len]);
 	set_din_type(&iv_seq[iv_seq_len], DMA_DLLI, ivgen_ctx->pool_meta_dma,
 		     SSI_IVPOOL_META_SIZE, NS_BIT);
 	set_dout_sram(&iv_seq[iv_seq_len], ivgen_ctx->pool,
 		      SSI_IVPOOL_META_SIZE);
 	set_flow_mode(&iv_seq[iv_seq_len], BYPASS);
 	iv_seq_len++;

 	/* Generate initial pool */
 	rc = ssi_ivgen_generate_pool(ivgen_ctx, iv_seq, &iv_seq_len);
 	if (unlikely(rc != 0))
 		return rc;

 	/* Fire-and-forget */
 	return send_request_init(drvdata, iv_seq, iv_seq_len);
 }

 /*!
  * Free iv-pool and ivgen context.
  *
  * \param drvdata
  */
 void ssi_ivgen_fini(struct ssi_drvdata *drvdata)
 {
 	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
 	struct device *device = &drvdata->plat_dev->dev;

 	if (!ivgen_ctx)
 		return;

 	if (ivgen_ctx->pool_meta) {
 		memset(ivgen_ctx->pool_meta, 0, SSI_IVPOOL_META_SIZE);
 		dma_free_coherent(device, SSI_IVPOOL_META_SIZE,
 				  ivgen_ctx->pool_meta,
 				  ivgen_ctx->pool_meta_dma);
 	}

 	ivgen_ctx->pool = NULL_SRAM_ADDR;

 	/* release "this" context */
 	kfree(ivgen_ctx);
 }

 /*!
  * Allocates iv-pool and maps resources.
  * This function generates the first IV pool.
  *
  * \param drvdata Driver's private context
  *
  * \return int Zero for success, negative value otherwise.
  */
 int ssi_ivgen_init(struct ssi_drvdata *drvdata)
 {
 	struct ssi_ivgen_ctx *ivgen_ctx;
 	struct device *device = &drvdata->plat_dev->dev;
 	int rc;

 	/* Allocate "this" context */
 	drvdata->ivgen_handle = kzalloc(sizeof(*drvdata->ivgen_handle),
 					GFP_KERNEL);
 	if (!drvdata->ivgen_handle) {
 		SSI_LOG_ERR("Not enough memory to allocate IVGEN context "
 			   "(%zu B)\n", sizeof(*drvdata->ivgen_handle));
 		rc = -ENOMEM;
 		goto out;
 	}
 	ivgen_ctx = drvdata->ivgen_handle;

 	/* Allocate pool's header for intial enc. key/IV */
 	ivgen_ctx->pool_meta = dma_alloc_coherent(device, SSI_IVPOOL_META_SIZE,
 						  &ivgen_ctx->pool_meta_dma,
 						  GFP_KERNEL);
 	if (!ivgen_ctx->pool_meta) {
 		SSI_LOG_ERR("Not enough memory to allocate DMA of pool_meta "
 			   "(%u B)\n", SSI_IVPOOL_META_SIZE);
 		rc = -ENOMEM;
 		goto out;
 	}
 	/* Allocate IV pool in SRAM */
 	ivgen_ctx->pool = ssi_sram_mgr_alloc(drvdata, SSI_IVPOOL_SIZE);
 	if (ivgen_ctx->pool == NULL_SRAM_ADDR) {
 		SSI_LOG_ERR("SRAM pool exhausted\n");
 		rc = -ENOMEM;
 		goto out;
 	}

 	return ssi_ivgen_init_sram_pool(drvdata);

 out:
 	ssi_ivgen_fini(drvdata);
 	return rc;
 }

 /*!
  * Acquires 16 Bytes IV from the iv-pool
  *
  * \param drvdata Driver private context
  * \param iv_out_dma Array of physical IV out addresses
  * \param iv_out_dma_len Length of iv_out_dma array (additional elements of iv_out_dma array are ignore)
  * \param iv_out_size May be 8 or 16 bytes long
  * \param iv_seq IN/OUT array to the descriptors sequence
  * \param iv_seq_len IN/OUT pointer to the sequence length
  *
  * \return int Zero for success, negative value otherwise.
  */
 int ssi_ivgen_getiv(
 	struct ssi_drvdata *drvdata,
 	dma_addr_t iv_out_dma[],
 	unsigned int iv_out_dma_len,
 	unsigned int iv_out_size,
 	struct cc_hw_desc iv_seq[],
 	unsigned int *iv_seq_len)
 {
 	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
 	unsigned int idx = *iv_seq_len;
 	unsigned int t;

 	if ((iv_out_size != CC_AES_IV_SIZE) &&
 	    (iv_out_size != CTR_RFC3686_IV_SIZE)) {
 		return -EINVAL;
 	}
 	if ((iv_out_dma_len + 1) > SSI_IVPOOL_SEQ_LEN) {
 		/* The sequence will be longer than allowed */
 		return -EINVAL;
 	}

 	//check that number of generated IV is limited to max dma address iv buffer size
 	if (iv_out_dma_len > SSI_MAX_IVGEN_DMA_ADDRESSES) {
 		/* The sequence will be longer than allowed */
 		return -EINVAL;
 	}

 	for (t = 0; t < iv_out_dma_len; t++) {
 		/* Acquire IV from pool */
 		hw_desc_init(&iv_seq[idx]);
 		set_din_sram(&iv_seq[idx], (ivgen_ctx->pool +
 					    ivgen_ctx->next_iv_ofs),
 			     iv_out_size);
 		set_dout_dlli(&iv_seq[idx], iv_out_dma[t], iv_out_size,
 			      NS_BIT, 0);
 		set_flow_mode(&iv_seq[idx], BYPASS);
 		idx++;
 	}

 	/* Bypass operation is proceeded by crypto sequence, hence must
 	 *  assure bypass-write-transaction by a memory barrier
 	 */
 	hw_desc_init(&iv_seq[idx]);
 	set_din_no_dma(&iv_seq[idx], 0, 0xfffff0);
 	set_dout_no_dma(&iv_seq[idx], 0, 0, 1);
 	idx++;

 	*iv_seq_len = idx; /* update seq length */

 	/* Update iv index */
 	ivgen_ctx->next_iv_ofs += iv_out_size;

 	if ((SSI_IVPOOL_SIZE - ivgen_ctx->next_iv_ofs) < CC_AES_IV_SIZE) {
 		SSI_LOG_DEBUG("Pool exhausted, regenerating iv-pool\n");
 		/* pool is drained -regenerate it! */
 		return ssi_ivgen_generate_pool(ivgen_ctx, iv_seq, iv_seq_len);
 	}

 	return 0;
 }
	/*
	* Copyright (C) 2012-2017 ARM Limited or its affiliates.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, see <http://www.gnu.org/licenses/>.
	*/

	#include <linux/platform_device.h>
	#include <crypto/ctr.h>
	#include "ssi_config.h"
	#include "ssi_driver.h"
	#include "ssi_ivgen.h"
	#include "ssi_request_mgr.h"
	#include "ssi_sram_mgr.h"
	#include "ssi_buffer_mgr.h"

	/* The max. size of pool MUST be <= SRAM total size */
	#define SSI_IVPOOL_SIZE 1024
	/* The first 32B fraction of pool are dedicated to the
	* next encryption "key" & "IV" for pool regeneration
	*/
	#define SSI_IVPOOL_META_SIZE (CC_AES_IV_SIZE + AES_KEYSIZE_128)
	#define SSI_IVPOOL_GEN_SEQ_LEN 4

	/**
	* struct ssi_ivgen_ctx -IV pool generation context
	* @pool: the start address of the iv-pool resides in internal RAM
	* @ctr_key_dma: address of pool's encryption key material in internal RAM
	* @ctr_iv_dma: address of pool's counter iv in internal RAM
	* @next_iv_ofs: the offset to the next available IV in pool
	* @pool_meta: virt. address of the initial enc. key/IV
	* @pool_meta_dma: phys. address of the initial enc. key/IV
	*/
	struct ssi_ivgen_ctx {
	ssi_sram_addr_t pool;
	ssi_sram_addr_t ctr_key;
	ssi_sram_addr_t ctr_iv;
	u32 next_iv_ofs;
	u8 *pool_meta;
	dma_addr_t pool_meta_dma;
	};

	/*!
	* Generates SSI_IVPOOL_SIZE of random bytes by
	* encrypting 0's using AES128-CTR.
	*
	* \param ivgen iv-pool context
	* \param iv_seq IN/OUT array to the descriptors sequence
	* \param iv_seq_len IN/OUT pointer to the sequence length
	*/
	static int ssi_ivgen_generate_pool(
	struct ssi_ivgen_ctx *ivgen_ctx,
	struct cc_hw_desc iv_seq[],
	unsigned int *iv_seq_len)
	{
	unsigned int idx = *iv_seq_len;

	if ((*iv_seq_len + SSI_IVPOOL_GEN_SEQ_LEN) > SSI_IVPOOL_SEQ_LEN) {
	/* The sequence will be longer than allowed */
	return -EINVAL;
	}
	/* Setup key */
	hw_desc_init(&iv_seq[idx]);
	set_din_sram(&iv_seq[idx], ivgen_ctx->ctr_key, AES_KEYSIZE_128);
	set_setup_mode(&iv_seq[idx], SETUP_LOAD_KEY0);
	set_cipher_config0(&iv_seq[idx], DESC_DIRECTION_ENCRYPT_ENCRYPT);
	set_flow_mode(&iv_seq[idx], S_DIN_to_AES);
	set_key_size_aes(&iv_seq[idx], CC_AES_128_BIT_KEY_SIZE);
	set_cipher_mode(&iv_seq[idx], DRV_CIPHER_CTR);
	idx++;

	/* Setup cipher state */
	hw_desc_init(&iv_seq[idx]);
	set_din_sram(&iv_seq[idx], ivgen_ctx->ctr_iv, CC_AES_IV_SIZE);
	set_cipher_config0(&iv_seq[idx], DESC_DIRECTION_ENCRYPT_ENCRYPT);
	set_flow_mode(&iv_seq[idx], S_DIN_to_AES);
	set_setup_mode(&iv_seq[idx], SETUP_LOAD_STATE1);
	set_key_size_aes(&iv_seq[idx], CC_AES_128_BIT_KEY_SIZE);
	set_cipher_mode(&iv_seq[idx], DRV_CIPHER_CTR);
	idx++;

	/* Perform dummy encrypt to skip first block */
	hw_desc_init(&iv_seq[idx]);
	set_din_const(&iv_seq[idx], 0, CC_AES_IV_SIZE);
	set_dout_sram(&iv_seq[idx], ivgen_ctx->pool, CC_AES_IV_SIZE);
	set_flow_mode(&iv_seq[idx], DIN_AES_DOUT);
	idx++;

	/* Generate IV pool */
	hw_desc_init(&iv_seq[idx]);
	set_din_const(&iv_seq[idx], 0, SSI_IVPOOL_SIZE);
	set_dout_sram(&iv_seq[idx], ivgen_ctx->pool, SSI_IVPOOL_SIZE);
	set_flow_mode(&iv_seq[idx], DIN_AES_DOUT);
	idx++;

	iv_seq_len = idx; / Update sequence length */

	/* queue ordering assures pool readiness */
	ivgen_ctx->next_iv_ofs = SSI_IVPOOL_META_SIZE;

	return 0;
	}

	/*!
	* Generates the initial pool in SRAM.
	* This function should be invoked when resuming DX driver.
	*
	* \param drvdata
	*
	* \return int Zero for success, negative value otherwise.
	*/
	int ssi_ivgen_init_sram_pool(struct ssi_drvdata *drvdata)
	{
	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
	struct cc_hw_desc iv_seq[SSI_IVPOOL_SEQ_LEN];
	unsigned int iv_seq_len = 0;
	int rc;

	/* Generate initial enc. key/iv */
	get_random_bytes(ivgen_ctx->pool_meta, SSI_IVPOOL_META_SIZE);

	/* The first 32B reserved for the enc. Key/IV */
	ivgen_ctx->ctr_key = ivgen_ctx->pool;
	ivgen_ctx->ctr_iv = ivgen_ctx->pool + AES_KEYSIZE_128;

	/* Copy initial enc. key and IV to SRAM at a single descriptor */
	hw_desc_init(&iv_seq[iv_seq_len]);
	set_din_type(&iv_seq[iv_seq_len], DMA_DLLI, ivgen_ctx->pool_meta_dma,
	SSI_IVPOOL_META_SIZE, NS_BIT);
	set_dout_sram(&iv_seq[iv_seq_len], ivgen_ctx->pool,
	SSI_IVPOOL_META_SIZE);
	set_flow_mode(&iv_seq[iv_seq_len], BYPASS);
	iv_seq_len++;

	/* Generate initial pool */
	rc = ssi_ivgen_generate_pool(ivgen_ctx, iv_seq, &iv_seq_len);
	if (unlikely(rc != 0))
	return rc;

	/* Fire-and-forget */
	return send_request_init(drvdata, iv_seq, iv_seq_len);
	}

	/*!
	* Free iv-pool and ivgen context.
	*
	* \param drvdata
	*/
	void ssi_ivgen_fini(struct ssi_drvdata *drvdata)
	{
	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
	struct device *device = &drvdata->plat_dev->dev;

	if (!ivgen_ctx)
	return;

	if (ivgen_ctx->pool_meta) {
	memset(ivgen_ctx->pool_meta, 0, SSI_IVPOOL_META_SIZE);
	dma_free_coherent(device, SSI_IVPOOL_META_SIZE,
	ivgen_ctx->pool_meta,
	ivgen_ctx->pool_meta_dma);
	}

	ivgen_ctx->pool = NULL_SRAM_ADDR;

	/* release "this" context */
	kfree(ivgen_ctx);
	}

	/*!
	* Allocates iv-pool and maps resources.
	* This function generates the first IV pool.
	*
	* \param drvdata Driver's private context
	*
	* \return int Zero for success, negative value otherwise.
	*/
	int ssi_ivgen_init(struct ssi_drvdata *drvdata)
	{
	struct ssi_ivgen_ctx *ivgen_ctx;
	struct device *device = &drvdata->plat_dev->dev;
	int rc;

	/* Allocate "this" context */
	drvdata->ivgen_handle = kzalloc(sizeof(*drvdata->ivgen_handle),
	GFP_KERNEL);
	if (!drvdata->ivgen_handle) {
	SSI_LOG_ERR("Not enough memory to allocate IVGEN context "
	"(%zu B)\n", sizeof(*drvdata->ivgen_handle));
	rc = -ENOMEM;
	goto out;
	}
	ivgen_ctx = drvdata->ivgen_handle;

	/* Allocate pool's header for intial enc. key/IV */
	ivgen_ctx->pool_meta = dma_alloc_coherent(device, SSI_IVPOOL_META_SIZE,
	&ivgen_ctx->pool_meta_dma,
	GFP_KERNEL);
	if (!ivgen_ctx->pool_meta) {
	SSI_LOG_ERR("Not enough memory to allocate DMA of pool_meta "
	"(%u B)\n", SSI_IVPOOL_META_SIZE);
	rc = -ENOMEM;
	goto out;
	}
	/* Allocate IV pool in SRAM */
	ivgen_ctx->pool = ssi_sram_mgr_alloc(drvdata, SSI_IVPOOL_SIZE);
	if (ivgen_ctx->pool == NULL_SRAM_ADDR) {
	SSI_LOG_ERR("SRAM pool exhausted\n");
	rc = -ENOMEM;
	goto out;
	}

	return ssi_ivgen_init_sram_pool(drvdata);

	out:
	ssi_ivgen_fini(drvdata);
	return rc;
	}

	/*!
	* Acquires 16 Bytes IV from the iv-pool
	*
	* \param drvdata Driver private context
	* \param iv_out_dma Array of physical IV out addresses
	* \param iv_out_dma_len Length of iv_out_dma array (additional elements of iv_out_dma array are ignore)
	* \param iv_out_size May be 8 or 16 bytes long
	* \param iv_seq IN/OUT array to the descriptors sequence
	* \param iv_seq_len IN/OUT pointer to the sequence length
	*
	* \return int Zero for success, negative value otherwise.
	*/
	int ssi_ivgen_getiv(
	struct ssi_drvdata *drvdata,
	dma_addr_t iv_out_dma[],
	unsigned int iv_out_dma_len,
	unsigned int iv_out_size,
	struct cc_hw_desc iv_seq[],
	unsigned int *iv_seq_len)
	{
	struct ssi_ivgen_ctx *ivgen_ctx = drvdata->ivgen_handle;
	unsigned int idx = *iv_seq_len;
	unsigned int t;

	if ((iv_out_size != CC_AES_IV_SIZE) &&
	(iv_out_size != CTR_RFC3686_IV_SIZE)) {
	return -EINVAL;
	}
	if ((iv_out_dma_len + 1) > SSI_IVPOOL_SEQ_LEN) {
	/* The sequence will be longer than allowed */
	return -EINVAL;
	}

	//check that number of generated IV is limited to max dma address iv buffer size
	if (iv_out_dma_len > SSI_MAX_IVGEN_DMA_ADDRESSES) {
	/* The sequence will be longer than allowed */
	return -EINVAL;
	}

	for (t = 0; t < iv_out_dma_len; t++) {
	/* Acquire IV from pool */
	hw_desc_init(&iv_seq[idx]);
	set_din_sram(&iv_seq[idx], (ivgen_ctx->pool +
	ivgen_ctx->next_iv_ofs),
	iv_out_size);
	set_dout_dlli(&iv_seq[idx], iv_out_dma[t], iv_out_size,
	NS_BIT, 0);
	set_flow_mode(&iv_seq[idx], BYPASS);
	idx++;
	}

	/* Bypass operation is proceeded by crypto sequence, hence must
	* assure bypass-write-transaction by a memory barrier
	*/
	hw_desc_init(&iv_seq[idx]);
	set_din_no_dma(&iv_seq[idx], 0, 0xfffff0);
	set_dout_no_dma(&iv_seq[idx], 0, 0, 1);
	idx++;

	iv_seq_len = idx; / update seq length */

	/* Update iv index */
	ivgen_ctx->next_iv_ofs += iv_out_size;

	if ((SSI_IVPOOL_SIZE - ivgen_ctx->next_iv_ofs) < CC_AES_IV_SIZE) {
	SSI_LOG_DEBUG("Pool exhausted, regenerating iv-pool\n");
	/* pool is drained -regenerate it! */
	return ssi_ivgen_generate_pool(ivgen_ctx, iv_seq, iv_seq_len);
	}

	return 0;
	}