// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2012-2019 ARM Limited (or its affiliates). */

#include <linux/kernel.h>
#include <linux/nospec.h>
#include "cc_driver.h"
#include "cc_buffer_mgr.h"
#include "cc_request_mgr.h"
#include "cc_pm.h"

#define CC_MAX_POLL_ITER        10
/* The highest descriptor count in used */
#define CC_MAX_DESC_SEQ_LEN     23

struct cc_req_mgr_handle {
        /* Request manager resources */
        unsigned int hw_queue_size; /* HW capability */
        unsigned int min_free_hw_slots;
        unsigned int max_used_sw_slots;
        struct cc_crypto_req req_queue[MAX_REQUEST_QUEUE_SIZE];
        u32 req_queue_head;
        u32 req_queue_tail;
        u32 axi_completed;
        u32 q_free_slots;
        /* This lock protects access to HW register
         * that must be single request at a time
         */
        spinlock_t hw_lock;
        struct cc_hw_desc compl_desc;
        u8 *dummy_comp_buff;
        dma_addr_t dummy_comp_buff_dma;

        /* backlog queue */
        struct list_head backlog;
        unsigned int bl_len;
        spinlock_t bl_lock; /* protect backlog queue */

#ifdef COMP_IN_WQ
        struct workqueue_struct *workq;
        struct delayed_work compwork;
#else
        struct tasklet_struct comptask;
#endif
};

struct cc_bl_item {
        struct cc_crypto_req creq;
        struct cc_hw_desc desc[CC_MAX_DESC_SEQ_LEN];
        unsigned int len;
        struct list_head list;
        bool notif;
};

static const u32 cc_cpp_int_masks[CC_CPP_NUM_ALGS][CC_CPP_NUM_SLOTS] = {
        { BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_0_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_1_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_2_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_3_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_4_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_5_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_6_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_AES_7_INT_BIT_SHIFT) },
        { BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_0_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_1_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_2_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_3_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_4_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_5_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_6_INT_BIT_SHIFT),
          BIT(CC_HOST_IRR_REE_OP_ABORTED_SM_7_INT_BIT_SHIFT) }
};

static void comp_handler(unsigned long devarg);
#ifdef COMP_IN_WQ
static void comp_work_handler(struct work_struct *work);
#endif

static inline u32 cc_cpp_int_mask(enum cc_cpp_alg alg, int slot)
{
        alg = array_index_nospec(alg, CC_CPP_NUM_ALGS);
        slot = array_index_nospec(slot, CC_CPP_NUM_SLOTS);

        return cc_cpp_int_masks[alg][slot];
}

void cc_req_mgr_fini(struct cc_drvdata *drvdata)
{
        struct cc_req_mgr_handle *req_mgr_h = drvdata->request_mgr_handle;
        struct device *dev = drvdata_to_dev(drvdata);

        if (!req_mgr_h)
                return; /* Not allocated */

        if (req_mgr_h->dummy_comp_buff_dma) {
                dma_free_coherent(dev, sizeof(u32), req_mgr_h->dummy_comp_buff,
                                  req_mgr_h->dummy_comp_buff_dma);
        }

        dev_dbg(dev, "max_used_hw_slots=%d\n", (req_mgr_h->hw_queue_size -
                                                req_mgr_h->min_free_hw_slots));
        dev_dbg(dev, "max_used_sw_slots=%d\n", req_mgr_h->max_used_sw_slots);

#ifdef COMP_IN_WQ
        destroy_workqueue(req_mgr_h->workq);
#else
        /* Kill tasklet */
        tasklet_kill(&req_mgr_h->comptask);
#endif
        kfree_sensitive(req_mgr_h);
        drvdata->request_mgr_handle = NULL;
}

int cc_req_mgr_init(struct cc_drvdata *drvdata)
{
        struct cc_req_mgr_handle *req_mgr_h;
        struct device *dev = drvdata_to_dev(drvdata);
        int rc = 0;

        req_mgr_h = kzalloc_obj(*req_mgr_h);
        if (!req_mgr_h) {
                rc = -ENOMEM;
                goto req_mgr_init_err;
        }

        drvdata->request_mgr_handle = req_mgr_h;

        spin_lock_init(&req_mgr_h->hw_lock);
        spin_lock_init(&req_mgr_h->bl_lock);
        INIT_LIST_HEAD(&req_mgr_h->backlog);

#ifdef COMP_IN_WQ
        dev_dbg(dev, "Initializing completion workqueue\n");
        req_mgr_h->workq = create_singlethread_workqueue("ccree");
        if (!req_mgr_h->workq) {
                dev_err(dev, "Failed creating work queue\n");
                rc = -ENOMEM;
                goto req_mgr_init_err;
        }
        INIT_DELAYED_WORK(&req_mgr_h->compwork, comp_work_handler);
#else
        dev_dbg(dev, "Initializing completion tasklet\n");
        tasklet_init(&req_mgr_h->comptask, comp_handler,
                     (unsigned long)drvdata);
#endif
        req_mgr_h->hw_queue_size = cc_ioread(drvdata,
                                             CC_REG(DSCRPTR_QUEUE_SRAM_SIZE));
        dev_dbg(dev, "hw_queue_size=0x%08X\n", req_mgr_h->hw_queue_size);
        if (req_mgr_h->hw_queue_size < MIN_HW_QUEUE_SIZE) {
                dev_err(dev, "Invalid HW queue size = %u (Min. required is %u)\n",
                        req_mgr_h->hw_queue_size, MIN_HW_QUEUE_SIZE);
                rc = -ENOMEM;
                goto req_mgr_init_err;
        }
        req_mgr_h->min_free_hw_slots = req_mgr_h->hw_queue_size;
        req_mgr_h->max_used_sw_slots = 0;

        /* Allocate DMA word for "dummy" completion descriptor use */
        req_mgr_h->dummy_comp_buff =
                dma_alloc_coherent(dev, sizeof(u32),
                                   &req_mgr_h->dummy_comp_buff_dma,
                                   GFP_KERNEL);
        if (!req_mgr_h->dummy_comp_buff) {
                dev_err(dev, "Not enough memory to allocate DMA (%zu) dropped buffer\n",
                        sizeof(u32));
                rc = -ENOMEM;
                goto req_mgr_init_err;
        }

        /* Init. "dummy" completion descriptor */
        hw_desc_init(&req_mgr_h->compl_desc);
        set_din_const(&req_mgr_h->compl_desc, 0, sizeof(u32));
        set_dout_dlli(&req_mgr_h->compl_desc, req_mgr_h->dummy_comp_buff_dma,
                      sizeof(u32), NS_BIT, 1);
        set_flow_mode(&req_mgr_h->compl_desc, BYPASS);
        set_queue_last_ind(drvdata, &req_mgr_h->compl_desc);

        return 0;

req_mgr_init_err:
        cc_req_mgr_fini(drvdata);
        return rc;
}

static void enqueue_seq(struct cc_drvdata *drvdata, struct cc_hw_desc seq[],
                        unsigned int seq_len)
{
        int i, w;
        void __iomem *reg = drvdata->cc_base + CC_REG(DSCRPTR_QUEUE_WORD0);
        struct device *dev = drvdata_to_dev(drvdata);

        /*
         * We do indeed write all 6 command words to the same
         * register. The HW supports this.
         */

        for (i = 0; i < seq_len; i++) {
                for (w = 0; w <= 5; w++)
                        writel_relaxed(seq[i].word[w], reg);

                if (cc_dump_desc)
                        dev_dbg(dev, "desc[%02d]: 0x%08X 0x%08X 0x%08X 0x%08X 0x%08X 0x%08X\n",
                                i, seq[i].word[0], seq[i].word[1],
                                seq[i].word[2], seq[i].word[3],
                                seq[i].word[4], seq[i].word[5]);
        }
}

/**
 * request_mgr_complete() - Completion will take place if and only if user
 * requested completion by cc_send_sync_request().
 *
 * @dev: Device pointer
 * @dx_compl_h: The completion event to signal
 * @dummy: unused error code
 */
static void request_mgr_complete(struct device *dev, void *dx_compl_h,
                                 int dummy)
{
        struct completion *this_compl = dx_compl_h;

        complete(this_compl);
}

static int cc_queues_status(struct cc_drvdata *drvdata,
                            struct cc_req_mgr_handle *req_mgr_h,
                            unsigned int total_seq_len)
{
        unsigned long poll_queue;
        struct device *dev = drvdata_to_dev(drvdata);

        /* SW queue is checked only once as it will not
         * be changed during the poll because the spinlock_bh
         * is held by the thread
         */
        if (((req_mgr_h->req_queue_head + 1) & (MAX_REQUEST_QUEUE_SIZE - 1)) ==
            req_mgr_h->req_queue_tail) {
                dev_err(dev, "SW FIFO is full. req_queue_head=%d sw_fifo_len=%d\n",
                        req_mgr_h->req_queue_head, MAX_REQUEST_QUEUE_SIZE);
                return -ENOSPC;
        }

        if (req_mgr_h->q_free_slots >= total_seq_len)
                return 0;

        /* Wait for space in HW queue. Poll constant num of iterations. */
        for (poll_queue = 0; poll_queue < CC_MAX_POLL_ITER ; poll_queue++) {
                req_mgr_h->q_free_slots =
                        cc_ioread(drvdata, CC_REG(DSCRPTR_QUEUE_CONTENT));
                if (req_mgr_h->q_free_slots < req_mgr_h->min_free_hw_slots)
                        req_mgr_h->min_free_hw_slots = req_mgr_h->q_free_slots;

                if (req_mgr_h->q_free_slots >= total_seq_len) {
                        /* If there is enough place return */
                        return 0;
                }

                dev_dbg(dev, "HW FIFO is full. q_free_slots=%d total_seq_len=%d\n",
                        req_mgr_h->q_free_slots, total_seq_len);
        }
        /* No room in the HW queue try again later */
        dev_dbg(dev, "HW FIFO full, timeout. req_queue_head=%d sw_fifo_len=%d q_free_slots=%d total_seq_len=%d\n",
                req_mgr_h->req_queue_head, MAX_REQUEST_QUEUE_SIZE,
                req_mgr_h->q_free_slots, total_seq_len);
        return -ENOSPC;
}

/**
 * cc_do_send_request() - Enqueue caller request to crypto hardware.
 * Need to be called with HW lock held and PM running
 *
 * @drvdata: Associated device driver context
 * @cc_req: The request to enqueue
 * @desc: The crypto sequence
 * @len: The crypto sequence length
 * @add_comp: If "true": add an artificial dout DMA to mark completion
 *
 */
static void cc_do_send_request(struct cc_drvdata *drvdata,
                               struct cc_crypto_req *cc_req,
                               struct cc_hw_desc *desc, unsigned int len,
                               bool add_comp)
{
        struct cc_req_mgr_handle *req_mgr_h = drvdata->request_mgr_handle;
        unsigned int used_sw_slots;
        unsigned int total_seq_len = len; /*initial sequence length*/
        struct device *dev = drvdata_to_dev(drvdata);

        used_sw_slots = ((req_mgr_h->req_queue_head -
                          req_mgr_h->req_queue_tail) &
                         (MAX_REQUEST_QUEUE_SIZE - 1));
        if (used_sw_slots > req_mgr_h->max_used_sw_slots)
                req_mgr_h->max_used_sw_slots = used_sw_slots;

        /* Enqueue request - must be locked with HW lock*/
        req_mgr_h->req_queue[req_mgr_h->req_queue_head] = *cc_req;
        req_mgr_h->req_queue_head = (req_mgr_h->req_queue_head + 1) &
                                    (MAX_REQUEST_QUEUE_SIZE - 1);

        dev_dbg(dev, "Enqueue request head=%u\n", req_mgr_h->req_queue_head);

        /*
         * We are about to push command to the HW via the command registers
         * that may reference host memory. We need to issue a memory barrier
         * to make sure there are no outstanding memory writes
         */
        wmb();

        /* STAT_PHASE_4: Push sequence */

        enqueue_seq(drvdata, desc, len);

        if (add_comp) {
                enqueue_seq(drvdata, &req_mgr_h->compl_desc, 1);
                total_seq_len++;
        }

        if (req_mgr_h->q_free_slots < total_seq_len) {
                /* This situation should never occur. Maybe indicating problem
                 * with resuming power. Set the free slot count to 0 and hope
                 * for the best.
                 */
                dev_err(dev, "HW free slot count mismatch.");
                req_mgr_h->q_free_slots = 0;
        } else {
                /* Update the free slots in HW queue */
                req_mgr_h->q_free_slots -= total_seq_len;
        }
}

static void cc_enqueue_backlog(struct cc_drvdata *drvdata,
                               struct cc_bl_item *bli)
{
        struct cc_req_mgr_handle *mgr = drvdata->request_mgr_handle;
        struct device *dev = drvdata_to_dev(drvdata);

        spin_lock_bh(&mgr->bl_lock);
        list_add_tail(&bli->list, &mgr->backlog);
        ++mgr->bl_len;
        dev_dbg(dev, "+++bl len: %d\n", mgr->bl_len);
        spin_unlock_bh(&mgr->bl_lock);
        tasklet_schedule(&mgr->comptask);
}

static void cc_proc_backlog(struct cc_drvdata *drvdata)
{
        struct cc_req_mgr_handle *mgr = drvdata->request_mgr_handle;
        struct cc_bl_item *bli;
        struct cc_crypto_req *creq;
        void *req;
        struct device *dev = drvdata_to_dev(drvdata);
        int rc;

        spin_lock(&mgr->bl_lock);

        while (mgr->bl_len) {
                bli = list_first_entry(&mgr->backlog, struct cc_bl_item, list);
                dev_dbg(dev, "---bl len: %d\n", mgr->bl_len);

                spin_unlock(&mgr->bl_lock);


                creq = &bli->creq;
                req = creq->user_arg;

                /*
                 * Notify the request we're moving out of the backlog
                 * but only if we haven't done so already.
                 */
                if (!bli->notif) {
                        creq->user_cb(dev, req, -EINPROGRESS);
                        bli->notif = true;
                }

                spin_lock(&mgr->hw_lock);

                rc = cc_queues_status(drvdata, mgr, bli->len);
                if (rc) {
                        /*
                         * There is still no room in the FIFO for
                         * this request. Bail out. We'll return here
                         * on the next completion irq.
                         */
                        spin_unlock(&mgr->hw_lock);
                        return;
                }

                cc_do_send_request(drvdata, &bli->creq, bli->desc, bli->len,
                                   false);
                spin_unlock(&mgr->hw_lock);

                /* Remove ourselves from the backlog list */
                spin_lock(&mgr->bl_lock);
                list_del(&bli->list);
                --mgr->bl_len;
                kfree(bli);
        }

        spin_unlock(&mgr->bl_lock);
}

int cc_send_request(struct cc_drvdata *drvdata, struct cc_crypto_req *cc_req,
                    struct cc_hw_desc *desc, unsigned int len,
                    struct crypto_async_request *req)
{
        int rc;
        struct cc_req_mgr_handle *mgr = drvdata->request_mgr_handle;
        struct device *dev = drvdata_to_dev(drvdata);
        bool backlog_ok = req->flags & CRYPTO_TFM_REQ_MAY_BACKLOG;
        gfp_t flags = cc_gfp_flags(req);
        struct cc_bl_item *bli;

        rc = cc_pm_get(dev);
        if (rc) {
                dev_err(dev, "cc_pm_get returned %x\n", rc);
                return rc;
        }

        spin_lock_bh(&mgr->hw_lock);
        rc = cc_queues_status(drvdata, mgr, len);

#ifdef CC_DEBUG_FORCE_BACKLOG
        if (backlog_ok)
                rc = -ENOSPC;
#endif /* CC_DEBUG_FORCE_BACKLOG */

        if (rc == -ENOSPC && backlog_ok) {
                spin_unlock_bh(&mgr->hw_lock);

                bli = kmalloc_obj(*bli, flags);
                if (!bli) {
                        cc_pm_put_suspend(dev);
                        return -ENOMEM;
                }

                memcpy(&bli->creq, cc_req, sizeof(*cc_req));
                memcpy(&bli->desc, desc, len * sizeof(*desc));
                bli->len = len;
                bli->notif = false;
                cc_enqueue_backlog(drvdata, bli);
                return -EBUSY;
        }

        if (!rc) {
                cc_do_send_request(drvdata, cc_req, desc, len, false);
                rc = -EINPROGRESS;
        }

        spin_unlock_bh(&mgr->hw_lock);
        return rc;
}

int cc_send_sync_request(struct cc_drvdata *drvdata,
                         struct cc_crypto_req *cc_req, struct cc_hw_desc *desc,
                         unsigned int len)
{
        int rc;
        struct device *dev = drvdata_to_dev(drvdata);
        struct cc_req_mgr_handle *mgr = drvdata->request_mgr_handle;

        init_completion(&cc_req->seq_compl);
        cc_req->user_cb = request_mgr_complete;
        cc_req->user_arg = &cc_req->seq_compl;

        rc = cc_pm_get(dev);
        if (rc) {
                dev_err(dev, "cc_pm_get returned %x\n", rc);
                return rc;
        }

        while (true) {
                spin_lock_bh(&mgr->hw_lock);
                rc = cc_queues_status(drvdata, mgr, len + 1);

                if (!rc)
                        break;

                spin_unlock_bh(&mgr->hw_lock);
                wait_for_completion_interruptible(&drvdata->hw_queue_avail);
                reinit_completion(&drvdata->hw_queue_avail);
        }

        cc_do_send_request(drvdata, cc_req, desc, len, true);
        spin_unlock_bh(&mgr->hw_lock);
        wait_for_completion(&cc_req->seq_compl);
        return 0;
}

/**
 * send_request_init() - Enqueue caller request to crypto hardware during init
 * process.
 * Assume this function is not called in the middle of a flow,
 * since we set QUEUE_LAST_IND flag in the last descriptor.
 *
 * @drvdata: Associated device driver context
 * @desc: The crypto sequence
 * @len: The crypto sequence length
 *
 * Return:
 * Returns "0" upon success
 */
int send_request_init(struct cc_drvdata *drvdata, struct cc_hw_desc *desc,
                      unsigned int len)
{
        struct cc_req_mgr_handle *req_mgr_h = drvdata->request_mgr_handle;
        unsigned int total_seq_len = len; /*initial sequence length*/
        int rc = 0;

        /* Wait for space in HW and SW FIFO. Poll for as much as FIFO_TIMEOUT.
         */
        rc = cc_queues_status(drvdata, req_mgr_h, total_seq_len);
        if (rc)
                return rc;

        set_queue_last_ind(drvdata, &desc[(len - 1)]);

        /*
         * We are about to push command to the HW via the command registers
         * that may reference host memory. We need to issue a memory barrier
         * to make sure there are no outstanding memory writes
         */
        wmb();
        enqueue_seq(drvdata, desc, len);

        /* Update the free slots in HW queue */
        req_mgr_h->q_free_slots =
                cc_ioread(drvdata, CC_REG(DSCRPTR_QUEUE_CONTENT));

        return 0;
}

void complete_request(struct cc_drvdata *drvdata)
{
        struct cc_req_mgr_handle *request_mgr_handle =
                                                drvdata->request_mgr_handle;

        complete(&drvdata->hw_queue_avail);
#ifdef COMP_IN_WQ
        queue_delayed_work(request_mgr_handle->workq,
                           &request_mgr_handle->compwork, 0);
#else
        tasklet_schedule(&request_mgr_handle->comptask);
#endif
}

#ifdef COMP_IN_WQ
static void comp_work_handler(struct work_struct *work)
{
        struct cc_drvdata *drvdata =
                container_of(work, struct cc_drvdata, compwork.work);

        comp_handler((unsigned long)drvdata);
}
#endif

static void proc_completions(struct cc_drvdata *drvdata)
{
        struct cc_crypto_req *cc_req;
        struct device *dev = drvdata_to_dev(drvdata);
        struct cc_req_mgr_handle *request_mgr_handle =
                                                drvdata->request_mgr_handle;
        unsigned int *tail = &request_mgr_handle->req_queue_tail;
        unsigned int *head = &request_mgr_handle->req_queue_head;
        int rc;
        u32 mask;

        while (request_mgr_handle->axi_completed) {
                request_mgr_handle->axi_completed--;

                /* Dequeue request */
                if (*head == *tail) {
                        /* We are supposed to handle a completion but our
                         * queue is empty. This is not normal. Return and
                         * hope for the best.
                         */
                        dev_err(dev, "Request queue is empty head == tail %u\n",
                                *head);
                        break;
                }

                cc_req = &request_mgr_handle->req_queue[*tail];

                if (cc_req->cpp.is_cpp) {

                        dev_dbg(dev, "CPP request completion slot: %d alg:%d\n",
                                cc_req->cpp.slot, cc_req->cpp.alg);
                        mask = cc_cpp_int_mask(cc_req->cpp.alg,
                                               cc_req->cpp.slot);
                        rc = (drvdata->irq & mask ? -EPERM : 0);
                        dev_dbg(dev, "Got mask: %x irq: %x rc: %d\n", mask,
                                drvdata->irq, rc);
                } else {
                        dev_dbg(dev, "None CPP request completion\n");
                        rc = 0;
                }

                if (cc_req->user_cb)
                        cc_req->user_cb(dev, cc_req->user_arg, rc);
                *tail = (*tail + 1) & (MAX_REQUEST_QUEUE_SIZE - 1);
                dev_dbg(dev, "Dequeue request tail=%u\n", *tail);
                dev_dbg(dev, "Request completed. axi_completed=%d\n",
                        request_mgr_handle->axi_completed);
                cc_pm_put_suspend(dev);
        }
}

static inline u32 cc_axi_comp_count(struct cc_drvdata *drvdata)
{
        return FIELD_GET(AXIM_MON_COMP_VALUE,
                         cc_ioread(drvdata, drvdata->axim_mon_offset));
}

/* Deferred service handler, run as interrupt-fired tasklet */
static void comp_handler(unsigned long devarg)
{
        struct cc_drvdata *drvdata = (struct cc_drvdata *)devarg;
        struct cc_req_mgr_handle *request_mgr_handle =
                                                drvdata->request_mgr_handle;
        struct device *dev = drvdata_to_dev(drvdata);
        u32 irq;

        dev_dbg(dev, "Completion handler called!\n");
        irq = (drvdata->irq & drvdata->comp_mask);

        /* To avoid the interrupt from firing as we unmask it,
         * we clear it now
         */
        cc_iowrite(drvdata, CC_REG(HOST_ICR), irq);

        /* Avoid race with above clear: Test completion counter once more */

        request_mgr_handle->axi_completed += cc_axi_comp_count(drvdata);

        dev_dbg(dev, "AXI completion after updated: %d\n",
                request_mgr_handle->axi_completed);

        while (request_mgr_handle->axi_completed) {
                do {
                        drvdata->irq |= cc_ioread(drvdata, CC_REG(HOST_IRR));
                        irq = (drvdata->irq & drvdata->comp_mask);
                        proc_completions(drvdata);

                        /* At this point (after proc_completions()),
                         * request_mgr_handle->axi_completed is 0.
                         */
                        request_mgr_handle->axi_completed +=
                                                cc_axi_comp_count(drvdata);
                } while (request_mgr_handle->axi_completed > 0);

                cc_iowrite(drvdata, CC_REG(HOST_ICR), irq);

                request_mgr_handle->axi_completed += cc_axi_comp_count(drvdata);
        }

        /* after verifying that there is nothing to do,
         * unmask AXI completion interrupt
         */
        cc_iowrite(drvdata, CC_REG(HOST_IMR),
                   cc_ioread(drvdata, CC_REG(HOST_IMR)) & ~drvdata->comp_mask);

        cc_proc_backlog(drvdata);
        dev_dbg(dev, "Comp. handler done.\n");
}