// SPDX-License-Identifier: GPL-2.0-only
/*
 * Intel Keem Bay OCS AES Crypto Driver.
 *
 * Copyright (C) 2018-2020 Intel Corporation
 */

#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/swab.h>

#include <asm/byteorder.h>
#include <asm/errno.h>

#include <crypto/aes.h>
#include <crypto/gcm.h>

#include "ocs-aes.h"

#define AES_COMMAND_OFFSET                      0x0000
#define AES_KEY_0_OFFSET                        0x0004
#define AES_KEY_1_OFFSET                        0x0008
#define AES_KEY_2_OFFSET                        0x000C
#define AES_KEY_3_OFFSET                        0x0010
#define AES_KEY_4_OFFSET                        0x0014
#define AES_KEY_5_OFFSET                        0x0018
#define AES_KEY_6_OFFSET                        0x001C
#define AES_KEY_7_OFFSET                        0x0020
#define AES_IV_0_OFFSET                         0x0024
#define AES_IV_1_OFFSET                         0x0028
#define AES_IV_2_OFFSET                         0x002C
#define AES_IV_3_OFFSET                         0x0030
#define AES_ACTIVE_OFFSET                       0x0034
#define AES_STATUS_OFFSET                       0x0038
#define AES_KEY_SIZE_OFFSET                     0x0044
#define AES_IER_OFFSET                          0x0048
#define AES_ISR_OFFSET                          0x005C
#define AES_MULTIPURPOSE1_0_OFFSET              0x0200
#define AES_MULTIPURPOSE1_1_OFFSET              0x0204
#define AES_MULTIPURPOSE1_2_OFFSET              0x0208
#define AES_MULTIPURPOSE1_3_OFFSET              0x020C
#define AES_MULTIPURPOSE2_0_OFFSET              0x0220
#define AES_MULTIPURPOSE2_1_OFFSET              0x0224
#define AES_MULTIPURPOSE2_2_OFFSET              0x0228
#define AES_MULTIPURPOSE2_3_OFFSET              0x022C
#define AES_BYTE_ORDER_CFG_OFFSET               0x02C0
#define AES_TLEN_OFFSET                         0x0300
#define AES_T_MAC_0_OFFSET                      0x0304
#define AES_T_MAC_1_OFFSET                      0x0308
#define AES_T_MAC_2_OFFSET                      0x030C
#define AES_T_MAC_3_OFFSET                      0x0310
#define AES_PLEN_OFFSET                         0x0314
#define AES_A_DMA_SRC_ADDR_OFFSET               0x0400
#define AES_A_DMA_DST_ADDR_OFFSET               0x0404
#define AES_A_DMA_SRC_SIZE_OFFSET               0x0408
#define AES_A_DMA_DST_SIZE_OFFSET               0x040C
#define AES_A_DMA_DMA_MODE_OFFSET               0x0410
#define AES_A_DMA_NEXT_SRC_DESCR_OFFSET         0x0418
#define AES_A_DMA_NEXT_DST_DESCR_OFFSET         0x041C
#define AES_A_DMA_WHILE_ACTIVE_MODE_OFFSET      0x0420
#define AES_A_DMA_LOG_OFFSET                    0x0424
#define AES_A_DMA_STATUS_OFFSET                 0x0428
#define AES_A_DMA_PERF_CNTR_OFFSET              0x042C
#define AES_A_DMA_MSI_ISR_OFFSET                0x0480
#define AES_A_DMA_MSI_IER_OFFSET                0x0484
#define AES_A_DMA_MSI_MASK_OFFSET               0x0488
#define AES_A_DMA_INBUFFER_WRITE_FIFO_OFFSET    0x0600
#define AES_A_DMA_OUTBUFFER_READ_FIFO_OFFSET    0x0700

/*
 * AES_A_DMA_DMA_MODE register.
 * Default: 0x00000000.
 * bit[31]      ACTIVE
 *              This bit activates the DMA. When the DMA finishes, it resets
 *              this bit to zero.
 * bit[30:26]   Unused by this driver.
 * bit[25]      SRC_LINK_LIST_EN
 *              Source link list enable bit. When the linked list is terminated
 *              this bit is reset by the DMA.
 * bit[24]      DST_LINK_LIST_EN
 *              Destination link list enable bit. When the linked list is
 *              terminated this bit is reset by the DMA.
 * bit[23:0]    Unused by this driver.
 */
#define AES_A_DMA_DMA_MODE_ACTIVE               BIT(31)
#define AES_A_DMA_DMA_MODE_SRC_LINK_LIST_EN     BIT(25)
#define AES_A_DMA_DMA_MODE_DST_LINK_LIST_EN     BIT(24)

/*
 * AES_ACTIVE register
 * default 0x00000000
 * bit[31:10]   Reserved
 * bit[9]       LAST_ADATA
 * bit[8]       LAST_GCX
 * bit[7:2]     Reserved
 * bit[1]       TERMINATION
 * bit[0]       TRIGGER
 */
#define AES_ACTIVE_LAST_ADATA                   BIT(9)
#define AES_ACTIVE_LAST_CCM_GCM                 BIT(8)
#define AES_ACTIVE_TERMINATION                  BIT(1)
#define AES_ACTIVE_TRIGGER                      BIT(0)

#define AES_DISABLE_INT                         0x00000000
#define AES_DMA_CPD_ERR_INT                     BIT(8)
#define AES_DMA_OUTBUF_RD_ERR_INT               BIT(7)
#define AES_DMA_OUTBUF_WR_ERR_INT               BIT(6)
#define AES_DMA_INBUF_RD_ERR_INT                BIT(5)
#define AES_DMA_INBUF_WR_ERR_INT                BIT(4)
#define AES_DMA_BAD_COMP_INT                    BIT(3)
#define AES_DMA_SAI_INT                         BIT(2)
#define AES_DMA_SRC_DONE_INT                    BIT(0)
#define AES_COMPLETE_INT                        BIT(1)

#define AES_DMA_MSI_MASK_CLEAR                  BIT(0)

#define AES_128_BIT_KEY                         0x00000000
#define AES_256_BIT_KEY                         BIT(0)

#define AES_DEACTIVATE_PERF_CNTR                0x00000000
#define AES_ACTIVATE_PERF_CNTR                  BIT(0)

#define AES_MAX_TAG_SIZE_U32                    4

#define OCS_LL_DMA_FLAG_TERMINATE               BIT(31)

/*
 * There is an inconsistency in the documentation. This is documented as a
 * 11-bit value, but it is actually 10-bits.
 */
#define AES_DMA_STATUS_INPUT_BUFFER_OCCUPANCY_MASK      0x3FF

/*
 * During CCM decrypt, the OCS block needs to finish processing the ciphertext
 * before the tag is written. For 128-bit mode this required delay is 28 OCS
 * clock cycles. For 256-bit mode it is 36 OCS clock cycles.
 */
#define CCM_DECRYPT_DELAY_TAG_CLK_COUNT         36UL

/*
 * During CCM decrypt there must be a delay of at least 42 OCS clock cycles
 * between setting the TRIGGER bit in AES_ACTIVE and setting the LAST_CCM_GCM
 * bit in the same register (as stated in the OCS databook)
 */
#define CCM_DECRYPT_DELAY_LAST_GCX_CLK_COUNT    42UL

/* See RFC3610 section 2.2 */
#define L_PRIME_MIN (1)
#define L_PRIME_MAX (7)
/*
 * CCM IV format from RFC 3610 section 2.3
 *
 *   Octet Number   Contents
 *   ------------   ---------
 *   0              Flags
 *   1 ... 15-L     Nonce N
 *   16-L ... 15    Counter i
 *
 * Flags = L' = L - 1
 */
#define L_PRIME_IDX             0
#define COUNTER_START(lprime)   (16 - ((lprime) + 1))
#define COUNTER_LEN(lprime)     ((lprime) + 1)

enum aes_counter_mode {
        AES_CTR_M_NO_INC = 0,
        AES_CTR_M_32_INC = 1,
        AES_CTR_M_64_INC = 2,
        AES_CTR_M_128_INC = 3,
};

/**
 * struct ocs_dma_linked_list - OCS DMA linked list entry.
 * @src_addr:   Source address of the data.
 * @src_len:    Length of data to be fetched.
 * @next:       Next dma_list to fetch.
 * @ll_flags:   Flags (Freeze @ terminate) for the DMA engine.
 */
struct ocs_dma_linked_list {
        u32 src_addr;
        u32 src_len;
        u32 next;
        u32 ll_flags;
} __packed;

/*
 * Set endianness of inputs and outputs
 * AES_BYTE_ORDER_CFG
 * default 0x00000000
 * bit [10] - KEY_HI_LO_SWAP
 * bit [9] - KEY_HI_SWAP_DWORDS_IN_OCTWORD
 * bit [8] - KEY_HI_SWAP_BYTES_IN_DWORD
 * bit [7] - KEY_LO_SWAP_DWORDS_IN_OCTWORD
 * bit [6] - KEY_LO_SWAP_BYTES_IN_DWORD
 * bit [5] - IV_SWAP_DWORDS_IN_OCTWORD
 * bit [4] - IV_SWAP_BYTES_IN_DWORD
 * bit [3] - DOUT_SWAP_DWORDS_IN_OCTWORD
 * bit [2] - DOUT_SWAP_BYTES_IN_DWORD
 * bit [1] - DOUT_SWAP_DWORDS_IN_OCTWORD
 * bit [0] - DOUT_SWAP_BYTES_IN_DWORD
 */
static inline void aes_a_set_endianness(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(0x7FF, aes_dev->base_reg + AES_BYTE_ORDER_CFG_OFFSET);
}

/* Trigger AES process start. */
static inline void aes_a_op_trigger(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_ACTIVE_TRIGGER, aes_dev->base_reg + AES_ACTIVE_OFFSET);
}

/* Indicate last bulk of data. */
static inline void aes_a_op_termination(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_ACTIVE_TERMINATION,
                  aes_dev->base_reg + AES_ACTIVE_OFFSET);
}

/*
 * Set LAST_CCM_GCM in AES_ACTIVE register and clear all other bits.
 *
 * Called when DMA is programmed to fetch the last batch of data.
 * - For AES-CCM it is called for the last batch of Payload data and Ciphertext
 *   data.
 * - For AES-GCM, it is called for the last batch of Plaintext data and
 *   Ciphertext data.
 */
static inline void aes_a_set_last_gcx(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_ACTIVE_LAST_CCM_GCM,
                  aes_dev->base_reg + AES_ACTIVE_OFFSET);
}

/* Wait for LAST_CCM_GCM bit to be unset. */
static inline void aes_a_wait_last_gcx(const struct ocs_aes_dev *aes_dev)
{
        u32 aes_active_reg;

        do {
                aes_active_reg = ioread32(aes_dev->base_reg +
                                          AES_ACTIVE_OFFSET);
        } while (aes_active_reg & AES_ACTIVE_LAST_CCM_GCM);
}

/* Wait for 10 bits of input occupancy. */
static void aes_a_dma_wait_input_buffer_occupancy(const struct ocs_aes_dev *aes_dev)
{
        u32 reg;

        do {
                reg = ioread32(aes_dev->base_reg + AES_A_DMA_STATUS_OFFSET);
        } while (reg & AES_DMA_STATUS_INPUT_BUFFER_OCCUPANCY_MASK);
}

 /*
  * Set LAST_CCM_GCM and LAST_ADATA bits in AES_ACTIVE register (and clear all
  * other bits).
  *
  * Called when DMA is programmed to fetch the last batch of Associated Data
  * (CCM case) or Additional Authenticated Data (GCM case).
  */
static inline void aes_a_set_last_gcx_and_adata(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_ACTIVE_LAST_ADATA | AES_ACTIVE_LAST_CCM_GCM,
                  aes_dev->base_reg + AES_ACTIVE_OFFSET);
}

/* Set DMA src and dst transfer size to 0 */
static inline void aes_a_dma_set_xfer_size_zero(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(0, aes_dev->base_reg + AES_A_DMA_SRC_SIZE_OFFSET);
        iowrite32(0, aes_dev->base_reg + AES_A_DMA_DST_SIZE_OFFSET);
}

/* Activate DMA for zero-byte transfer case. */
static inline void aes_a_dma_active(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_A_DMA_DMA_MODE_ACTIVE,
                  aes_dev->base_reg + AES_A_DMA_DMA_MODE_OFFSET);
}

/* Activate DMA and enable src linked list */
static inline void aes_a_dma_active_src_ll_en(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_A_DMA_DMA_MODE_ACTIVE |
                  AES_A_DMA_DMA_MODE_SRC_LINK_LIST_EN,
                  aes_dev->base_reg + AES_A_DMA_DMA_MODE_OFFSET);
}

/* Activate DMA and enable dst linked list */
static inline void aes_a_dma_active_dst_ll_en(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_A_DMA_DMA_MODE_ACTIVE |
                  AES_A_DMA_DMA_MODE_DST_LINK_LIST_EN,
                  aes_dev->base_reg + AES_A_DMA_DMA_MODE_OFFSET);
}

/* Activate DMA and enable src and dst linked lists */
static inline void aes_a_dma_active_src_dst_ll_en(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(AES_A_DMA_DMA_MODE_ACTIVE |
                  AES_A_DMA_DMA_MODE_SRC_LINK_LIST_EN |
                  AES_A_DMA_DMA_MODE_DST_LINK_LIST_EN,
                  aes_dev->base_reg + AES_A_DMA_DMA_MODE_OFFSET);
}

/* Reset PERF_CNTR to 0 and activate it */
static inline void aes_a_dma_reset_and_activate_perf_cntr(const struct ocs_aes_dev *aes_dev)
{
        iowrite32(0x00000000, aes_dev->base_reg + AES_A_DMA_PERF_CNTR_OFFSET);
        iowrite32(AES_ACTIVATE_PERF_CNTR,
                  aes_dev->base_reg + AES_A_DMA_WHILE_ACTIVE_MODE_OFFSET);
}

/* Wait until PERF_CNTR is > delay, then deactivate it */
static inline void aes_a_dma_wait_and_deactivate_perf_cntr(const struct ocs_aes_dev *aes_dev,
                                                           int delay)
{
        while (ioread32(aes_dev->base_reg + AES_A_DMA_PERF_CNTR_OFFSET) < delay)
                ;
        iowrite32(AES_DEACTIVATE_PERF_CNTR,
                  aes_dev->base_reg + AES_A_DMA_WHILE_ACTIVE_MODE_OFFSET);
}

/* Disable AES and DMA IRQ. */
static void aes_irq_disable(struct ocs_aes_dev *aes_dev)
{
        u32 isr_val = 0;

        /* Disable interrupts */
        iowrite32(AES_DISABLE_INT,
                  aes_dev->base_reg + AES_A_DMA_MSI_IER_OFFSET);
        iowrite32(AES_DISABLE_INT, aes_dev->base_reg + AES_IER_OFFSET);

        /* Clear any pending interrupt */
        isr_val = ioread32(aes_dev->base_reg + AES_A_DMA_MSI_ISR_OFFSET);
        if (isr_val)
                iowrite32(isr_val,
                          aes_dev->base_reg + AES_A_DMA_MSI_ISR_OFFSET);

        isr_val = ioread32(aes_dev->base_reg + AES_A_DMA_MSI_MASK_OFFSET);
        if (isr_val)
                iowrite32(isr_val,
                          aes_dev->base_reg + AES_A_DMA_MSI_MASK_OFFSET);

        isr_val = ioread32(aes_dev->base_reg + AES_ISR_OFFSET);
        if (isr_val)
                iowrite32(isr_val, aes_dev->base_reg + AES_ISR_OFFSET);
}

/* Enable AES or DMA IRQ.  IRQ is disabled once fired. */
static void aes_irq_enable(struct ocs_aes_dev *aes_dev, u8 irq)
{
        if (irq == AES_COMPLETE_INT) {
                /* Ensure DMA error interrupts are enabled */
                iowrite32(AES_DMA_CPD_ERR_INT |
                          AES_DMA_OUTBUF_RD_ERR_INT |
                          AES_DMA_OUTBUF_WR_ERR_INT |
                          AES_DMA_INBUF_RD_ERR_INT |
                          AES_DMA_INBUF_WR_ERR_INT |
                          AES_DMA_BAD_COMP_INT |
                          AES_DMA_SAI_INT,
                          aes_dev->base_reg + AES_A_DMA_MSI_IER_OFFSET);
                /*
                 * AES_IER
                 * default 0x00000000
                 * bits [31:3] - reserved
                 * bit [2] - EN_SKS_ERR
                 * bit [1] - EN_AES_COMPLETE
                 * bit [0] - reserved
                 */
                iowrite32(AES_COMPLETE_INT, aes_dev->base_reg + AES_IER_OFFSET);
                return;
        }
        if (irq == AES_DMA_SRC_DONE_INT) {
                /* Ensure AES interrupts are disabled */
                iowrite32(AES_DISABLE_INT, aes_dev->base_reg + AES_IER_OFFSET);
                /*
                 * DMA_MSI_IER
                 * default 0x00000000
                 * bits [31:9] - reserved
                 * bit [8] - CPD_ERR_INT_EN
                 * bit [7] - OUTBUF_RD_ERR_INT_EN
                 * bit [6] - OUTBUF_WR_ERR_INT_EN
                 * bit [5] - INBUF_RD_ERR_INT_EN
                 * bit [4] - INBUF_WR_ERR_INT_EN
                 * bit [3] - BAD_COMP_INT_EN
                 * bit [2] - SAI_INT_EN
                 * bit [1] - DST_DONE_INT_EN
                 * bit [0] - SRC_DONE_INT_EN
                 */
                iowrite32(AES_DMA_CPD_ERR_INT |
                          AES_DMA_OUTBUF_RD_ERR_INT |
                          AES_DMA_OUTBUF_WR_ERR_INT |
                          AES_DMA_INBUF_RD_ERR_INT |
                          AES_DMA_INBUF_WR_ERR_INT |
                          AES_DMA_BAD_COMP_INT |
                          AES_DMA_SAI_INT |
                          AES_DMA_SRC_DONE_INT,
                          aes_dev->base_reg + AES_A_DMA_MSI_IER_OFFSET);
        }
}

/* Enable and wait for IRQ (either from OCS AES engine or DMA) */
static int ocs_aes_irq_enable_and_wait(struct ocs_aes_dev *aes_dev, u8 irq)
{
        int rc;

        reinit_completion(&aes_dev->irq_completion);
        aes_irq_enable(aes_dev, irq);
        rc = wait_for_completion_interruptible(&aes_dev->irq_completion);
        if (rc)
                return rc;

        return aes_dev->dma_err_mask ? -EIO : 0;
}

/* Configure DMA to OCS, linked list mode */
static inline void dma_to_ocs_aes_ll(struct ocs_aes_dev *aes_dev,
                                     dma_addr_t dma_list)
{
        iowrite32(0, aes_dev->base_reg + AES_A_DMA_SRC_SIZE_OFFSET);
        iowrite32(dma_list,
                  aes_dev->base_reg + AES_A_DMA_NEXT_SRC_DESCR_OFFSET);
}

/* Configure DMA from OCS, linked list mode */
static inline void dma_from_ocs_aes_ll(struct ocs_aes_dev *aes_dev,
                                       dma_addr_t dma_list)
{
        iowrite32(0, aes_dev->base_reg + AES_A_DMA_DST_SIZE_OFFSET);
        iowrite32(dma_list,
                  aes_dev->base_reg + AES_A_DMA_NEXT_DST_DESCR_OFFSET);
}

irqreturn_t ocs_aes_irq_handler(int irq, void *dev_id)
{
        struct ocs_aes_dev *aes_dev = dev_id;
        u32 aes_dma_isr;

        /* Read DMA ISR status. */
        aes_dma_isr = ioread32(aes_dev->base_reg + AES_A_DMA_MSI_ISR_OFFSET);

        /* Disable and clear interrupts. */
        aes_irq_disable(aes_dev);

        /* Save DMA error status. */
        aes_dev->dma_err_mask = aes_dma_isr &
                                (AES_DMA_CPD_ERR_INT |
                                 AES_DMA_OUTBUF_RD_ERR_INT |
                                 AES_DMA_OUTBUF_WR_ERR_INT |
                                 AES_DMA_INBUF_RD_ERR_INT |
                                 AES_DMA_INBUF_WR_ERR_INT |
                                 AES_DMA_BAD_COMP_INT |
                                 AES_DMA_SAI_INT);

        /* Signal IRQ completion. */
        complete(&aes_dev->irq_completion);

        return IRQ_HANDLED;
}

/**
 * ocs_aes_set_key() - Write key into OCS AES hardware.
 * @aes_dev:    The OCS AES device to write the key to.
 * @key_size:   The size of the key (in bytes).
 * @key:        The key to write.
 * @cipher:     The cipher the key is for.
 *
 * For AES @key_size must be either 16 or 32. For SM4 @key_size must be 16.
 *
 * Return:      0 on success, negative error code otherwise.
 */
int ocs_aes_set_key(struct ocs_aes_dev *aes_dev, u32 key_size, const u8 *key,
                    enum ocs_cipher cipher)
{
        const u32 *key_u32;
        u32 val;
        int i;

        /* OCS AES supports 128-bit and 256-bit keys only. */
        if (cipher == OCS_AES && !(key_size == 32 || key_size == 16)) {
                dev_err(aes_dev->dev,
                        "%d-bit keys not supported by AES cipher\n",
                        key_size * 8);
                return -EINVAL;
        }
        /* OCS SM4 supports 128-bit keys only. */
        if (cipher == OCS_SM4 && key_size != 16) {
                dev_err(aes_dev->dev,
                        "%d-bit keys not supported for SM4 cipher\n",
                        key_size * 8);
                return -EINVAL;
        }

        if (!key)
                return -EINVAL;

        key_u32 = (const u32 *)key;

        /* Write key to AES_KEY[0-7] registers */
        for (i = 0; i < (key_size / sizeof(u32)); i++) {
                iowrite32(key_u32[i],
                          aes_dev->base_reg + AES_KEY_0_OFFSET +
                          (i * sizeof(u32)));
        }
        /*
         * Write key size
         * bits [31:1] - reserved
         * bit [0] - AES_KEY_SIZE
         *           0 - 128 bit key
         *           1 - 256 bit key
         */
        val = (key_size == 16) ? AES_128_BIT_KEY : AES_256_BIT_KEY;
        iowrite32(val, aes_dev->base_reg + AES_KEY_SIZE_OFFSET);

        return 0;
}

/* Write AES_COMMAND */
static inline void set_ocs_aes_command(struct ocs_aes_dev *aes_dev,
                                       enum ocs_cipher cipher,
                                       enum ocs_mode mode,
                                       enum ocs_instruction instruction)
{
        u32 val;

        /* AES_COMMAND
         * default 0x000000CC
         * bit [14] - CIPHER_SELECT
         *            0 - AES
         *            1 - SM4
         * bits [11:8] - OCS_AES_MODE
         *               0000 - ECB
         *               0001 - CBC
         *               0010 - CTR
         *               0110 - CCM
         *               0111 - GCM
         *               1001 - CTS
         * bits [7:6] - AES_INSTRUCTION
         *              00 - ENCRYPT
         *              01 - DECRYPT
         *              10 - EXPAND
         *              11 - BYPASS
         * bits [3:2] - CTR_M_BITS
         *              00 - No increment
         *              01 - Least significant 32 bits are incremented
         *              10 - Least significant 64 bits are incremented
         *              11 - Full 128 bits are incremented
         */
        val = (cipher << 14) | (mode << 8) | (instruction << 6) |
              (AES_CTR_M_128_INC << 2);
        iowrite32(val, aes_dev->base_reg + AES_COMMAND_OFFSET);
}

static void ocs_aes_init(struct ocs_aes_dev *aes_dev,
                         enum ocs_mode mode,
                         enum ocs_cipher cipher,
                         enum ocs_instruction instruction)
{
        /* Ensure interrupts are disabled and pending interrupts cleared. */
        aes_irq_disable(aes_dev);

        /* Set endianness recommended by data-sheet. */
        aes_a_set_endianness(aes_dev);

        /* Set AES_COMMAND register. */
        set_ocs_aes_command(aes_dev, cipher, mode, instruction);
}

/*
 * Write the byte length of the last AES/SM4 block of Payload data (without
 * zero padding and without the length of the MAC) in register AES_PLEN.
 */
static inline void ocs_aes_write_last_data_blk_len(struct ocs_aes_dev *aes_dev,
                                                   u32 size)
{
        u32 val;

        if (size == 0) {
                val = 0;
                goto exit;
        }

        val = size % AES_BLOCK_SIZE;
        if (val == 0)
                val = AES_BLOCK_SIZE;

exit:
        iowrite32(val, aes_dev->base_reg + AES_PLEN_OFFSET);
}

/*
 * Validate inputs according to mode.
 * If OK return 0; else return -EINVAL.
 */
static int ocs_aes_validate_inputs(dma_addr_t src_dma_list, u32 src_size,
                                   const u8 *iv, u32 iv_size,
                                   dma_addr_t aad_dma_list, u32 aad_size,
                                   const u8 *tag, u32 tag_size,
                                   enum ocs_cipher cipher, enum ocs_mode mode,
                                   enum ocs_instruction instruction,
                                   dma_addr_t dst_dma_list)
{
        /* Ensure cipher, mode and instruction are valid. */
        if (!(cipher == OCS_AES || cipher == OCS_SM4))
                return -EINVAL;

        if (mode != OCS_MODE_ECB && mode != OCS_MODE_CBC &&
            mode != OCS_MODE_CTR && mode != OCS_MODE_CCM &&
            mode != OCS_MODE_GCM && mode != OCS_MODE_CTS)
                return -EINVAL;

        if (instruction != OCS_ENCRYPT && instruction != OCS_DECRYPT &&
            instruction != OCS_EXPAND  && instruction != OCS_BYPASS)
                return -EINVAL;

        /*
         * When instruction is OCS_BYPASS, OCS simply copies data from source
         * to destination using DMA.
         *
         * AES mode is irrelevant, but both source and destination DMA
         * linked-list must be defined.
         */
        if (instruction == OCS_BYPASS) {
                if (src_dma_list == DMA_MAPPING_ERROR ||
                    dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                return 0;
        }

        /*
         * For performance reasons switch based on mode to limit unnecessary
         * conditionals for each mode
         */
        switch (mode) {
        case OCS_MODE_ECB:
                /* Ensure input length is multiple of block size */
                if (src_size % AES_BLOCK_SIZE != 0)
                        return -EINVAL;

                /* Ensure source and destination linked lists are created */
                if (src_dma_list == DMA_MAPPING_ERROR ||
                    dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                return 0;

        case OCS_MODE_CBC:
                /* Ensure input length is multiple of block size */
                if (src_size % AES_BLOCK_SIZE != 0)
                        return -EINVAL;

                /* Ensure source and destination linked lists are created */
                if (src_dma_list == DMA_MAPPING_ERROR ||
                    dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* Ensure IV is present and block size in length */
                if (!iv || iv_size != AES_BLOCK_SIZE)
                        return -EINVAL;

                return 0;

        case OCS_MODE_CTR:
                /* Ensure input length of 1 byte or greater */
                if (src_size == 0)
                        return -EINVAL;

                /* Ensure source and destination linked lists are created */
                if (src_dma_list == DMA_MAPPING_ERROR ||
                    dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* Ensure IV is present and block size in length */
                if (!iv || iv_size != AES_BLOCK_SIZE)
                        return -EINVAL;

                return 0;

        case OCS_MODE_CTS:
                /* Ensure input length >= block size */
                if (src_size < AES_BLOCK_SIZE)
                        return -EINVAL;

                /* Ensure source and destination linked lists are created */
                if (src_dma_list == DMA_MAPPING_ERROR ||
                    dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* Ensure IV is present and block size in length */
                if (!iv || iv_size != AES_BLOCK_SIZE)
                        return -EINVAL;

                return 0;

        case OCS_MODE_GCM:
                /* Ensure IV is present and GCM_AES_IV_SIZE in length */
                if (!iv || iv_size != GCM_AES_IV_SIZE)
                        return -EINVAL;

                /*
                 * If input data present ensure source and destination linked
                 * lists are created
                 */
                if (src_size && (src_dma_list == DMA_MAPPING_ERROR ||
                                 dst_dma_list == DMA_MAPPING_ERROR))
                        return -EINVAL;

                /* If aad present ensure aad linked list is created */
                if (aad_size && aad_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* Ensure tag destination is set */
                if (!tag)
                        return -EINVAL;

                /* Just ensure that tag_size doesn't cause overflows. */
                if (tag_size > (AES_MAX_TAG_SIZE_U32 * sizeof(u32)))
                        return -EINVAL;

                return 0;

        case OCS_MODE_CCM:
                /* Ensure IV is present and block size in length */
                if (!iv || iv_size != AES_BLOCK_SIZE)
                        return -EINVAL;

                /* 2 <= L <= 8, so 1 <= L' <= 7 */
                if (iv[L_PRIME_IDX] < L_PRIME_MIN ||
                    iv[L_PRIME_IDX] > L_PRIME_MAX)
                        return -EINVAL;

                /* If aad present ensure aad linked list is created */
                if (aad_size && aad_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* Just ensure that tag_size doesn't cause overflows. */
                if (tag_size > (AES_MAX_TAG_SIZE_U32 * sizeof(u32)))
                        return -EINVAL;

                if (instruction == OCS_DECRYPT) {
                        /*
                         * If input data present ensure source and destination
                         * linked lists are created
                         */
                        if (src_size && (src_dma_list == DMA_MAPPING_ERROR ||
                                         dst_dma_list == DMA_MAPPING_ERROR))
                                return -EINVAL;

                        /* Ensure input tag is present */
                        if (!tag)
                                return -EINVAL;

                        return 0;
                }

                /* Instruction == OCS_ENCRYPT */

                /*
                 * Destination linked list always required (for tag even if no
                 * input data)
                 */
                if (dst_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                /* If input data present ensure src linked list is created */
                if (src_size && src_dma_list == DMA_MAPPING_ERROR)
                        return -EINVAL;

                return 0;

        default:
                return -EINVAL;
        }
}

/**
 * ocs_aes_op() - Perform AES/SM4 operation.
 * @aes_dev:            The OCS AES device to use.
 * @mode:               The mode to use (ECB, CBC, CTR, or CTS).
 * @cipher:             The cipher to use (AES or SM4).
 * @instruction:        The instruction to perform (encrypt or decrypt).
 * @dst_dma_list:       The OCS DMA list mapping output memory.
 * @src_dma_list:       The OCS DMA list mapping input payload data.
 * @src_size:           The amount of data mapped by @src_dma_list.
 * @iv:                 The IV vector.
 * @iv_size:            The size (in bytes) of @iv.
 *
 * Return: 0 on success, negative error code otherwise.
 */
int ocs_aes_op(struct ocs_aes_dev *aes_dev,
               enum ocs_mode mode,
               enum ocs_cipher cipher,
               enum ocs_instruction instruction,
               dma_addr_t dst_dma_list,
               dma_addr_t src_dma_list,
               u32 src_size,
               u8 *iv,
               u32 iv_size)
{
        u32 *iv32;
        int rc;

        rc = ocs_aes_validate_inputs(src_dma_list, src_size, iv, iv_size, 0, 0,
                                     NULL, 0, cipher, mode, instruction,
                                     dst_dma_list);
        if (rc)
                return rc;
        /*
         * ocs_aes_validate_inputs() is a generic check, now ensure mode is not
         * GCM or CCM.
         */
        if (mode == OCS_MODE_GCM || mode == OCS_MODE_CCM)
                return -EINVAL;

        /* Cast IV to u32 array. */
        iv32 = (u32 *)iv;

        ocs_aes_init(aes_dev, mode, cipher, instruction);

        if (mode == OCS_MODE_CTS) {
                /* Write the byte length of the last data block to engine. */
                ocs_aes_write_last_data_blk_len(aes_dev, src_size);
        }

        /* ECB is the only mode that doesn't use IV. */
        if (mode != OCS_MODE_ECB) {
                iowrite32(iv32[0], aes_dev->base_reg + AES_IV_0_OFFSET);
                iowrite32(iv32[1], aes_dev->base_reg + AES_IV_1_OFFSET);
                iowrite32(iv32[2], aes_dev->base_reg + AES_IV_2_OFFSET);
                iowrite32(iv32[3], aes_dev->base_reg + AES_IV_3_OFFSET);
        }

        /* Set AES_ACTIVE.TRIGGER to start the operation. */
        aes_a_op_trigger(aes_dev);

        /* Configure and activate input / output DMA. */
        dma_to_ocs_aes_ll(aes_dev, src_dma_list);
        dma_from_ocs_aes_ll(aes_dev, dst_dma_list);
        aes_a_dma_active_src_dst_ll_en(aes_dev);

        if (mode == OCS_MODE_CTS) {
                /*
                 * For CTS mode, instruct engine to activate ciphertext
                 * stealing if last block of data is incomplete.
                 */
                aes_a_set_last_gcx(aes_dev);
        } else {
                /* For all other modes, just write the 'termination' bit. */
                aes_a_op_termination(aes_dev);
        }

        /* Wait for engine to complete processing. */
        rc = ocs_aes_irq_enable_and_wait(aes_dev, AES_COMPLETE_INT);
        if (rc)
                return rc;

        if (mode == OCS_MODE_CTR) {
                /* Read back IV for streaming mode */
                iv32[0] = ioread32(aes_dev->base_reg + AES_IV_0_OFFSET);
                iv32[1] = ioread32(aes_dev->base_reg + AES_IV_1_OFFSET);
                iv32[2] = ioread32(aes_dev->base_reg + AES_IV_2_OFFSET);
                iv32[3] = ioread32(aes_dev->base_reg + AES_IV_3_OFFSET);
        }

        return 0;
}

/* Compute and write J0 to engine registers. */
static void ocs_aes_gcm_write_j0(const struct ocs_aes_dev *aes_dev,
                                 const u8 *iv)
{
        const u32 *j0 = (u32 *)iv;

        /*
         * IV must be 12 bytes; Other sizes not supported as Linux crypto API
         * does only expects/allows 12 byte IV for GCM
         */
        iowrite32(0x00000001, aes_dev->base_reg + AES_IV_0_OFFSET);
        iowrite32(__swab32(j0[2]), aes_dev->base_reg + AES_IV_1_OFFSET);
        iowrite32(__swab32(j0[1]), aes_dev->base_reg + AES_IV_2_OFFSET);
        iowrite32(__swab32(j0[0]), aes_dev->base_reg + AES_IV_3_OFFSET);
}

/* Read GCM tag from engine registers. */
static inline void ocs_aes_gcm_read_tag(struct ocs_aes_dev *aes_dev,
                                        u8 *tag, u32 tag_size)
{
        u32 tag_u32[AES_MAX_TAG_SIZE_U32];

        /*
         * The Authentication Tag T is stored in Little Endian order in the
         * registers with the most significant bytes stored from AES_T_MAC[3]
         * downward.
         */
        tag_u32[0] = __swab32(ioread32(aes_dev->base_reg + AES_T_MAC_3_OFFSET));
        tag_u32[1] = __swab32(ioread32(aes_dev->base_reg + AES_T_MAC_2_OFFSET));
        tag_u32[2] = __swab32(ioread32(aes_dev->base_reg + AES_T_MAC_1_OFFSET));
        tag_u32[3] = __swab32(ioread32(aes_dev->base_reg + AES_T_MAC_0_OFFSET));

        memcpy(tag, tag_u32, tag_size);
}

/**
 * ocs_aes_gcm_op() - Perform GCM operation.
 * @aes_dev:            The OCS AES device to use.
 * @cipher:             The Cipher to use (AES or SM4).
 * @instruction:        The instruction to perform (encrypt or decrypt).
 * @dst_dma_list:       The OCS DMA list mapping output memory.
 * @src_dma_list:       The OCS DMA list mapping input payload data.
 * @src_size:           The amount of data mapped by @src_dma_list.
 * @iv:                 The input IV vector.
 * @aad_dma_list:       The OCS DMA list mapping input AAD data.
 * @aad_size:           The amount of data mapped by @aad_dma_list.
 * @out_tag:            Where to store computed tag.
 * @tag_size:           The size (in bytes) of @out_tag.
 *
 * Return: 0 on success, negative error code otherwise.
 */
int ocs_aes_gcm_op(struct ocs_aes_dev *aes_dev,
                   enum ocs_cipher cipher,
                   enum ocs_instruction instruction,
                   dma_addr_t dst_dma_list,
                   dma_addr_t src_dma_list,
                   u32 src_size,
                   const u8 *iv,
                   dma_addr_t aad_dma_list,
                   u32 aad_size,
                   u8 *out_tag,
                   u32 tag_size)
{
        u64 bit_len;
        u32 val;
        int rc;

        rc = ocs_aes_validate_inputs(src_dma_list, src_size, iv,
                                     GCM_AES_IV_SIZE, aad_dma_list,
                                     aad_size, out_tag, tag_size, cipher,
                                     OCS_MODE_GCM, instruction,
                                     dst_dma_list);
        if (rc)
                return rc;

        ocs_aes_init(aes_dev, OCS_MODE_GCM, cipher, instruction);

        /* Compute and write J0 to OCS HW. */
        ocs_aes_gcm_write_j0(aes_dev, iv);

        /* Write out_tag byte length */
        iowrite32(tag_size, aes_dev->base_reg + AES_TLEN_OFFSET);

        /* Write the byte length of the last plaintext / ciphertext block. */
        ocs_aes_write_last_data_blk_len(aes_dev, src_size);

        /* Write ciphertext bit length */
        bit_len = (u64)src_size * 8;
        val = bit_len & 0xFFFFFFFF;
        iowrite32(val, aes_dev->base_reg + AES_MULTIPURPOSE2_0_OFFSET);
        val = bit_len >> 32;
        iowrite32(val, aes_dev->base_reg + AES_MULTIPURPOSE2_1_OFFSET);

        /* Write aad bit length */
        bit_len = (u64)aad_size * 8;
        val = bit_len & 0xFFFFFFFF;
        iowrite32(val, aes_dev->base_reg + AES_MULTIPURPOSE2_2_OFFSET);
        val = bit_len >> 32;
        iowrite32(val, aes_dev->base_reg + AES_MULTIPURPOSE2_3_OFFSET);

        /* Set AES_ACTIVE.TRIGGER to start the operation. */
        aes_a_op_trigger(aes_dev);

        /* Process AAD. */
        if (aad_size) {
                /* If aad present, configure DMA to feed it to the engine. */
                dma_to_ocs_aes_ll(aes_dev, aad_dma_list);
                aes_a_dma_active_src_ll_en(aes_dev);

                /* Instructs engine to pad last block of aad, if needed. */
                aes_a_set_last_gcx_and_adata(aes_dev);

                /* Wait for DMA transfer to complete. */
                rc = ocs_aes_irq_enable_and_wait(aes_dev, AES_DMA_SRC_DONE_INT);
                if (rc)
                        return rc;
        } else {
                aes_a_set_last_gcx_and_adata(aes_dev);
        }

        /* Wait until adata (if present) has been processed. */
        aes_a_wait_last_gcx(aes_dev);
        aes_a_dma_wait_input_buffer_occupancy(aes_dev);

        /* Now process payload. */
        if (src_size) {
                /* Configure and activate DMA for both input and output data. */

                dma_to_ocs_aes_ll(aes_dev, src_dma_list);
                dma_from_ocs_aes_ll(aes_dev, dst_dma_list);
                aes_a_dma_active_src_dst_ll_en(aes_dev);
        } else {
                aes_a_dma_set_xfer_size_zero(aes_dev);
                aes_a_dma_active(aes_dev);
        }

        /* Instruct AES/SMA4 engine payload processing is over. */
        aes_a_set_last_gcx(aes_dev);

        /* Wait for OCS AES engine to complete processing. */
        rc = ocs_aes_irq_enable_and_wait(aes_dev, AES_COMPLETE_INT);
        if (rc)
                return rc;

        ocs_aes_gcm_read_tag(aes_dev, out_tag, tag_size);

        return 0;
}

/* Write encrypted tag to AES/SM4 engine. */
static void ocs_aes_ccm_write_encrypted_tag(struct ocs_aes_dev *aes_dev,
                                            const u8 *in_tag, u32 tag_size)
{
        int i;

        /* Ensure DMA input buffer is empty */
        aes_a_dma_wait_input_buffer_occupancy(aes_dev);

        /*
         * During CCM decrypt, the OCS block needs to finish processing the
         * ciphertext before the tag is written.  So delay needed after DMA has
         * completed writing the ciphertext
         */
        aes_a_dma_reset_and_activate_perf_cntr(aes_dev);
        aes_a_dma_wait_and_deactivate_perf_cntr(aes_dev,
                                                CCM_DECRYPT_DELAY_TAG_CLK_COUNT);

        /* Write encrypted tag to AES/SM4 engine. */
        for (i = 0; i < tag_size; i++) {
                iowrite8(in_tag[i], aes_dev->base_reg +
                                    AES_A_DMA_INBUFFER_WRITE_FIFO_OFFSET);
        }
}

/*
 * Write B0 CCM block to OCS AES HW.
 *
 * Note: B0 format is documented in NIST Special Publication 800-38C
 * https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38c.pdf
 * (see Section A.2.1)
 */
static int ocs_aes_ccm_write_b0(const struct ocs_aes_dev *aes_dev,
                                const u8 *iv, u32 adata_size, u32 tag_size,
                                u32 cryptlen)
{
        u8 b0[16]; /* CCM B0 block is 16 bytes long. */
        int i, q;

        /* Initialize B0 to 0. */
        memset(b0, 0, sizeof(b0));

        /*
         * B0[0] is the 'Flags Octet' and has the following structure:
         *   bit 7: Reserved
         *   bit 6: Adata flag
         *   bit 5-3: t value encoded as (t-2)/2
         *   bit 2-0: q value encoded as q - 1
         */
        /* If there is AAD data, set the Adata flag. */
        if (adata_size)
                b0[0] |= BIT(6);
        /*
         * t denotes the octet length of T.
         * t can only be an element of { 4, 6, 8, 10, 12, 14, 16} and is
         * encoded as (t - 2) / 2
         */
        b0[0] |= (((tag_size - 2) / 2) & 0x7)  << 3;
        /*
         * q is the octet length of Q.
         * q can only be an element of {2, 3, 4, 5, 6, 7, 8} and is encoded as
         * q - 1 == iv[0] & 0x7;
         */
        b0[0] |= iv[0] & 0x7;
        /*
         * Copy the Nonce N from IV to B0; N is located in iv[1]..iv[15 - q]
         * and must be copied to b0[1]..b0[15-q].
         * q == (iv[0] & 0x7) + 1
         */
        q = (iv[0] & 0x7) + 1;
        for (i = 1; i <= 15 - q; i++)
                b0[i] = iv[i];
        /*
         * The rest of B0 must contain Q, i.e., the message length.
         * Q is encoded in q octets, in big-endian order, so to write it, we
         * start from the end of B0 and we move backward.
         */
        i = sizeof(b0) - 1;
        while (q) {
                b0[i] = cryptlen & 0xff;
                cryptlen >>= 8;
                i--;
                q--;
        }
        /*
         * If cryptlen is not zero at this point, it means that its original
         * value was too big.
         */
        if (cryptlen)
                return -EOVERFLOW;
        /* Now write B0 to OCS AES input buffer. */
        for (i = 0; i < sizeof(b0); i++)
                iowrite8(b0[i], aes_dev->base_reg +
                                AES_A_DMA_INBUFFER_WRITE_FIFO_OFFSET);
        return 0;
}

/*
 * Write adata length to OCS AES HW.
 *
 * Note: adata len encoding is documented in NIST Special Publication 800-38C
 * https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38c.pdf
 * (see Section A.2.2)
 */
static void ocs_aes_ccm_write_adata_len(const struct ocs_aes_dev *aes_dev,
                                        u64 adata_len)
{
        u8 enc_a[10]; /* Maximum encoded size: 10 octets. */
        int i, len;

        /*
         * adata_len ('a') is encoded as follows:
         * If 0 < a < 2^16 - 2^8    ==> 'a' encoded as [a]16, i.e., two octets
         *                              (big endian).
         * If 2^16 - 2^8 ≤ a < 2^32 ==> 'a' encoded as 0xff || 0xfe || [a]32,
         *                              i.e., six octets (big endian).
         * If 2^32 ≤ a < 2^64       ==> 'a' encoded as 0xff || 0xff || [a]64,
         *                              i.e., ten octets (big endian).
         */
        if (adata_len < 65280) {
                len = 2;
                *(__be16 *)enc_a = cpu_to_be16(adata_len);
        } else if (adata_len <= 0xFFFFFFFF) {
                len = 6;
                *(__be16 *)enc_a = cpu_to_be16(0xfffe);
                *(__be32 *)&enc_a[2] = cpu_to_be32(adata_len);
        } else { /* adata_len >= 2^32 */
                len = 10;
                *(__be16 *)enc_a = cpu_to_be16(0xffff);
                *(__be64 *)&enc_a[2] = cpu_to_be64(adata_len);
        }
        for (i = 0; i < len; i++)
                iowrite8(enc_a[i],
                         aes_dev->base_reg +
                         AES_A_DMA_INBUFFER_WRITE_FIFO_OFFSET);
}

static int ocs_aes_ccm_do_adata(struct ocs_aes_dev *aes_dev,
                                dma_addr_t adata_dma_list, u32 adata_size)
{
        int rc;

        if (!adata_size) {
                /* Since no aad the LAST_GCX bit can be set now */
                aes_a_set_last_gcx_and_adata(aes_dev);
                goto exit;
        }

        /* Adata case. */

        /*
         * Form the encoding of the Associated data length and write it
         * to the AES/SM4 input buffer.
         */
        ocs_aes_ccm_write_adata_len(aes_dev, adata_size);

        /* Configure the AES/SM4 DMA to fetch the Associated Data */
        dma_to_ocs_aes_ll(aes_dev, adata_dma_list);

        /* Activate DMA to fetch Associated data. */
        aes_a_dma_active_src_ll_en(aes_dev);

        /* Set LAST_GCX and LAST_ADATA in AES ACTIVE register. */
        aes_a_set_last_gcx_and_adata(aes_dev);

        /* Wait for DMA transfer to complete. */
        rc = ocs_aes_irq_enable_and_wait(aes_dev, AES_DMA_SRC_DONE_INT);
        if (rc)
                return rc;

exit:
        /* Wait until adata (if present) has been processed. */
        aes_a_wait_last_gcx(aes_dev);
        aes_a_dma_wait_input_buffer_occupancy(aes_dev);

        return 0;
}

static int ocs_aes_ccm_encrypt_do_payload(struct ocs_aes_dev *aes_dev,
                                          dma_addr_t dst_dma_list,
                                          dma_addr_t src_dma_list,
                                          u32 src_size)
{
        if (src_size) {
                /*
                 * Configure and activate DMA for both input and output
                 * data.
                 */
                dma_to_ocs_aes_ll(aes_dev, src_dma_list);
                dma_from_ocs_aes_ll(aes_dev, dst_dma_list);
                aes_a_dma_active_src_dst_ll_en(aes_dev);
        } else {
                /* Configure and activate DMA for output data only. */
                dma_from_ocs_aes_ll(aes_dev, dst_dma_list);
                aes_a_dma_active_dst_ll_en(aes_dev);
        }

        /*
         * Set the LAST GCX bit in AES_ACTIVE Register to instruct
         * AES/SM4 engine to pad the last block of data.
         */
        aes_a_set_last_gcx(aes_dev);

        /* We are done, wait for IRQ and return. */
        return ocs_aes_irq_enable_and_wait(aes_dev, AES_COMPLETE_INT);
}

static int ocs_aes_ccm_decrypt_do_payload(struct ocs_aes_dev *aes_dev,
                                          dma_addr_t dst_dma_list,
                                          dma_addr_t src_dma_list,
                                          u32 src_size)
{
        if (!src_size) {
                /* Let engine process 0-length input. */
                aes_a_dma_set_xfer_size_zero(aes_dev);
                aes_a_dma_active(aes_dev);
                aes_a_set_last_gcx(aes_dev);

                return 0;
        }

        /*
         * Configure and activate DMA for both input and output
         * data.
         */
        dma_to_ocs_aes_ll(aes_dev, src_dma_list);
        dma_from_ocs_aes_ll(aes_dev, dst_dma_list);
        aes_a_dma_active_src_dst_ll_en(aes_dev);
        /*
         * Set the LAST GCX bit in AES_ACTIVE Register; this allows the
         * AES/SM4 engine to differentiate between encrypted data and
         * encrypted MAC.
         */
        aes_a_set_last_gcx(aes_dev);
         /*
          * Enable DMA DONE interrupt; once DMA transfer is over,
          * interrupt handler will process the MAC/tag.
          */
        return ocs_aes_irq_enable_and_wait(aes_dev, AES_DMA_SRC_DONE_INT);
}

/*
 * Compare Tag to Yr.
 *
 * Only used at the end of CCM decrypt. If tag == yr, message authentication
 * has succeeded.
 */
static inline int ccm_compare_tag_to_yr(struct ocs_aes_dev *aes_dev,
                                        u8 tag_size_bytes)
{
        u32 tag[AES_MAX_TAG_SIZE_U32];
        u32 yr[AES_MAX_TAG_SIZE_U32];
        u8 i;

        /* Read Tag and Yr from AES registers. */
        for (i = 0; i < AES_MAX_TAG_SIZE_U32; i++) {
                tag[i] = ioread32(aes_dev->base_reg +
                                  AES_T_MAC_0_OFFSET + (i * sizeof(u32)));
                yr[i] = ioread32(aes_dev->base_reg +
                                 AES_MULTIPURPOSE2_0_OFFSET +
                                 (i * sizeof(u32)));
        }

        return memcmp(tag, yr, tag_size_bytes) ? -EBADMSG : 0;
}

/**
 * ocs_aes_ccm_op() - Perform CCM operation.
 * @aes_dev:            The OCS AES device to use.
 * @cipher:             The Cipher to use (AES or SM4).
 * @instruction:        The instruction to perform (encrypt or decrypt).
 * @dst_dma_list:       The OCS DMA list mapping output memory.
 * @src_dma_list:       The OCS DMA list mapping input payload data.
 * @src_size:           The amount of data mapped by @src_dma_list.
 * @iv:                 The input IV vector.
 * @adata_dma_list:     The OCS DMA list mapping input A-data.
 * @adata_size:         The amount of data mapped by @adata_dma_list.
 * @in_tag:             Input tag.
 * @tag_size:           The size (in bytes) of @in_tag.
 *
 * Note: for encrypt the tag is appended to the ciphertext (in the memory
 *       mapped by @dst_dma_list).
 *
 * Return: 0 on success, negative error code otherwise.
 */
int ocs_aes_ccm_op(struct ocs_aes_dev *aes_dev,
                   enum ocs_cipher cipher,
                   enum ocs_instruction instruction,
                   dma_addr_t dst_dma_list,
                   dma_addr_t src_dma_list,
                   u32 src_size,
                   u8 *iv,
                   dma_addr_t adata_dma_list,
                   u32 adata_size,
                   u8 *in_tag,
                   u32 tag_size)
{
        u32 *iv_32;
        u8 lprime;
        int rc;

        rc = ocs_aes_validate_inputs(src_dma_list, src_size, iv,
                                     AES_BLOCK_SIZE, adata_dma_list, adata_size,
                                     in_tag, tag_size, cipher, OCS_MODE_CCM,
                                     instruction, dst_dma_list);
        if (rc)
                return rc;

        ocs_aes_init(aes_dev, OCS_MODE_CCM, cipher, instruction);

        /*
         * Note: rfc 3610 and NIST 800-38C require counter of zero to encrypt
         * auth tag so ensure this is the case
         */
        lprime = iv[L_PRIME_IDX];
        memset(&iv[COUNTER_START(lprime)], 0, COUNTER_LEN(lprime));

        /*
         * Nonce is already converted to ctr0 before being passed into this
         * function as iv.
         */
        iv_32 = (u32 *)iv;
        iowrite32(__swab32(iv_32[0]),
                  aes_dev->base_reg + AES_MULTIPURPOSE1_3_OFFSET);
        iowrite32(__swab32(iv_32[1]),
                  aes_dev->base_reg + AES_MULTIPURPOSE1_2_OFFSET);
        iowrite32(__swab32(iv_32[2]),
                  aes_dev->base_reg + AES_MULTIPURPOSE1_1_OFFSET);
        iowrite32(__swab32(iv_32[3]),
                  aes_dev->base_reg + AES_MULTIPURPOSE1_0_OFFSET);

        /* Write MAC/tag length in register AES_TLEN */
        iowrite32(tag_size, aes_dev->base_reg + AES_TLEN_OFFSET);
        /*
         * Write the byte length of the last AES/SM4 block of Payload data
         * (without zero padding and without the length of the MAC) in register
         * AES_PLEN.
         */
        ocs_aes_write_last_data_blk_len(aes_dev, src_size);

        /* Set AES_ACTIVE.TRIGGER to start the operation. */
        aes_a_op_trigger(aes_dev);

        aes_a_dma_reset_and_activate_perf_cntr(aes_dev);

        /* Form block B0 and write it to the AES/SM4 input buffer. */
        rc = ocs_aes_ccm_write_b0(aes_dev, iv, adata_size, tag_size, src_size);
        if (rc)
                return rc;
        /*
         * Ensure there has been at least CCM_DECRYPT_DELAY_LAST_GCX_CLK_COUNT
         * clock cycles since TRIGGER bit was set
         */
        aes_a_dma_wait_and_deactivate_perf_cntr(aes_dev,
                                                CCM_DECRYPT_DELAY_LAST_GCX_CLK_COUNT);

        /* Process Adata. */
        ocs_aes_ccm_do_adata(aes_dev, adata_dma_list, adata_size);

        /* For Encrypt case we just process the payload and return. */
        if (instruction == OCS_ENCRYPT) {
                return ocs_aes_ccm_encrypt_do_payload(aes_dev, dst_dma_list,
                                                      src_dma_list, src_size);
        }
        /* For Decypt we need to process the payload and then the tag. */
        rc = ocs_aes_ccm_decrypt_do_payload(aes_dev, dst_dma_list,
                                            src_dma_list, src_size);
        if (rc)
                return rc;

        /* Process MAC/tag directly: feed tag to engine and wait for IRQ. */
        ocs_aes_ccm_write_encrypted_tag(aes_dev, in_tag, tag_size);
        rc = ocs_aes_irq_enable_and_wait(aes_dev, AES_COMPLETE_INT);
        if (rc)
                return rc;

        return ccm_compare_tag_to_yr(aes_dev, tag_size);
}

/**
 * ocs_create_linked_list_from_sg() - Create OCS DMA linked list from SG list.
 * @aes_dev:      The OCS AES device the list will be created for.
 * @sg:           The SG list OCS DMA linked list will be created from. When
 *                passed to this function, @sg must have been already mapped
 *                with dma_map_sg().
 * @sg_dma_count: The number of DMA-mapped entries in @sg. This must be the
 *                value returned by dma_map_sg() when @sg was mapped.
 * @dll_desc:     The OCS DMA dma_list to use to store information about the
 *                created linked list.
 * @data_size:    The size of the data (from the SG list) to be mapped into the
 *                OCS DMA linked list.
 * @data_offset:  The offset (within the SG list) of the data to be mapped.
 *
 * Return:      0 on success, negative error code otherwise.
 */
int ocs_create_linked_list_from_sg(const struct ocs_aes_dev *aes_dev,
                                   struct scatterlist *sg,
                                   int sg_dma_count,
                                   struct ocs_dll_desc *dll_desc,
                                   size_t data_size, size_t data_offset)
{
        struct ocs_dma_linked_list *ll = NULL;
        struct scatterlist *sg_tmp;
        unsigned int tmp;
        int dma_nents;
        int i;

        if (!dll_desc || !sg || !aes_dev)
                return -EINVAL;

        /* Default values for when no ddl_desc is created. */
        dll_desc->vaddr = NULL;
        dll_desc->dma_addr = DMA_MAPPING_ERROR;
        dll_desc->size = 0;

        if (data_size == 0)
                return 0;

        /* Loop over sg_list until we reach entry at specified offset. */
        while (data_offset >= sg_dma_len(sg)) {
                data_offset -= sg_dma_len(sg);
                sg_dma_count--;
                sg = sg_next(sg);
                /* If we reach the end of the list, offset was invalid. */
                if (!sg || sg_dma_count == 0)
                        return -EINVAL;
        }

        /* Compute number of DMA-mapped SG entries to add into OCS DMA list. */
        dma_nents = 0;
        tmp = 0;
        sg_tmp = sg;
        while (tmp < data_offset + data_size) {
                /* If we reach the end of the list, data_size was invalid. */
                if (!sg_tmp)
                        return -EINVAL;
                tmp += sg_dma_len(sg_tmp);
                dma_nents++;
                sg_tmp = sg_next(sg_tmp);
        }
        if (dma_nents > sg_dma_count)
                return -EINVAL;

        /* Allocate the DMA list, one entry for each SG entry. */
        dll_desc->size = sizeof(struct ocs_dma_linked_list) * dma_nents;
        dll_desc->vaddr = dma_alloc_coherent(aes_dev->dev, dll_desc->size,
                                             &dll_desc->dma_addr, GFP_KERNEL);
        if (!dll_desc->vaddr)
                return -ENOMEM;

        /* Populate DMA linked list entries. */
        ll = dll_desc->vaddr;
        for (i = 0; i < dma_nents; i++, sg = sg_next(sg)) {
                ll[i].src_addr = sg_dma_address(sg) + data_offset;
                ll[i].src_len = (sg_dma_len(sg) - data_offset) < data_size ?
                                (sg_dma_len(sg) - data_offset) : data_size;
                data_offset = 0;
                data_size -= ll[i].src_len;
                /* Current element points to the DMA address of the next one. */
                ll[i].next = dll_desc->dma_addr + (sizeof(*ll) * (i + 1));
                ll[i].ll_flags = 0;
        }
        /* Terminate last element. */
        ll[i - 1].next = 0;
        ll[i - 1].ll_flags = OCS_LL_DMA_FLAG_TERMINATE;

        return 0;
}