Merge tag 'block-5.11-2021-01-10' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / dma / qcom / hidma_ll.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Qualcomm Technologies HIDMA DMA engine low level code
 *
 * Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
 */

#include <linux/dmaengine.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/atomic.h>
#include <linux/iopoll.h>
#include <linux/kfifo.h>
#include <linux/bitops.h>

#include "hidma.h"

#define HIDMA_EVRE_SIZE                 16      /* each EVRE is 16 bytes */

#define HIDMA_TRCA_CTRLSTS_REG                  0x000
#define HIDMA_TRCA_RING_LOW_REG         0x008
#define HIDMA_TRCA_RING_HIGH_REG                0x00C
#define HIDMA_TRCA_RING_LEN_REG         0x010
#define HIDMA_TRCA_DOORBELL_REG         0x400

#define HIDMA_EVCA_CTRLSTS_REG                  0x000
#define HIDMA_EVCA_INTCTRL_REG                  0x004
#define HIDMA_EVCA_RING_LOW_REG         0x008
#define HIDMA_EVCA_RING_HIGH_REG                0x00C
#define HIDMA_EVCA_RING_LEN_REG         0x010
#define HIDMA_EVCA_WRITE_PTR_REG                0x020
#define HIDMA_EVCA_DOORBELL_REG         0x400

#define HIDMA_EVCA_IRQ_STAT_REG         0x100
#define HIDMA_EVCA_IRQ_CLR_REG                  0x108
#define HIDMA_EVCA_IRQ_EN_REG                   0x110

#define HIDMA_EVRE_CFG_IDX                      0

#define HIDMA_EVRE_ERRINFO_BIT_POS              24
#define HIDMA_EVRE_CODE_BIT_POS         28

#define HIDMA_EVRE_ERRINFO_MASK         GENMASK(3, 0)
#define HIDMA_EVRE_CODE_MASK                    GENMASK(3, 0)

#define HIDMA_CH_CONTROL_MASK                   GENMASK(7, 0)
#define HIDMA_CH_STATE_MASK                     GENMASK(7, 0)
#define HIDMA_CH_STATE_BIT_POS                  0x8

#define HIDMA_IRQ_EV_CH_EOB_IRQ_BIT_POS 0
#define HIDMA_IRQ_EV_CH_WR_RESP_BIT_POS 1
#define HIDMA_IRQ_TR_CH_TRE_RD_RSP_ER_BIT_POS   9
#define HIDMA_IRQ_TR_CH_DATA_RD_ER_BIT_POS      10
#define HIDMA_IRQ_TR_CH_DATA_WR_ER_BIT_POS      11
#define HIDMA_IRQ_TR_CH_INVALID_TRE_BIT_POS     14

#define ENABLE_IRQS (BIT(HIDMA_IRQ_EV_CH_EOB_IRQ_BIT_POS)       | \
                     BIT(HIDMA_IRQ_EV_CH_WR_RESP_BIT_POS)       | \
                     BIT(HIDMA_IRQ_TR_CH_TRE_RD_RSP_ER_BIT_POS) | \
                     BIT(HIDMA_IRQ_TR_CH_DATA_RD_ER_BIT_POS)    | \
                     BIT(HIDMA_IRQ_TR_CH_DATA_WR_ER_BIT_POS)    | \
                     BIT(HIDMA_IRQ_TR_CH_INVALID_TRE_BIT_POS))

#define HIDMA_INCREMENT_ITERATOR(iter, size, ring_size) \
do {                                                            \
        iter += size;                                           \
        if (iter >= ring_size)                                  \
                iter -= ring_size;                              \
} while (0)

#define HIDMA_CH_STATE(val)     \
        ((val >> HIDMA_CH_STATE_BIT_POS) & HIDMA_CH_STATE_MASK)

#define HIDMA_ERR_INT_MASK                              \
        (BIT(HIDMA_IRQ_TR_CH_INVALID_TRE_BIT_POS)   |   \
         BIT(HIDMA_IRQ_TR_CH_TRE_RD_RSP_ER_BIT_POS) |   \
         BIT(HIDMA_IRQ_EV_CH_WR_RESP_BIT_POS)       |   \
         BIT(HIDMA_IRQ_TR_CH_DATA_RD_ER_BIT_POS)    |   \
         BIT(HIDMA_IRQ_TR_CH_DATA_WR_ER_BIT_POS))

enum ch_command {
        HIDMA_CH_DISABLE = 0,
        HIDMA_CH_ENABLE = 1,
        HIDMA_CH_SUSPEND = 2,
        HIDMA_CH_RESET = 9,
};

enum ch_state {
        HIDMA_CH_DISABLED = 0,
        HIDMA_CH_ENABLED = 1,
        HIDMA_CH_RUNNING = 2,
        HIDMA_CH_SUSPENDED = 3,
        HIDMA_CH_STOPPED = 4,
};

enum err_code {
        HIDMA_EVRE_STATUS_COMPLETE = 1,
        HIDMA_EVRE_STATUS_ERROR = 4,
};

static int hidma_is_chan_enabled(int state)
{
        switch (state) {
        case HIDMA_CH_ENABLED:
        case HIDMA_CH_RUNNING:
                return true;
        default:
                return false;
        }
}

void hidma_ll_free(struct hidma_lldev *lldev, u32 tre_ch)
{
        struct hidma_tre *tre;

        if (tre_ch >= lldev->nr_tres) {
                dev_err(lldev->dev, "invalid TRE number in free:%d", tre_ch);
                return;
        }

        tre = &lldev->trepool[tre_ch];
        if (atomic_read(&tre->allocated) != true) {
                dev_err(lldev->dev, "trying to free an unused TRE:%d", tre_ch);
                return;
        }

        atomic_set(&tre->allocated, 0);
}

int hidma_ll_request(struct hidma_lldev *lldev, u32 sig, const char *dev_name,
                     void (*callback)(void *data), void *data, u32 *tre_ch)
{
        unsigned int i;
        struct hidma_tre *tre;
        u32 *tre_local;

        if (!tre_ch || !lldev)
                return -EINVAL;

        /* need to have at least one empty spot in the queue */
        for (i = 0; i < lldev->nr_tres - 1; i++) {
                if (atomic_add_unless(&lldev->trepool[i].allocated, 1, 1))
                        break;
        }

        if (i == (lldev->nr_tres - 1))
                return -ENOMEM;

        tre = &lldev->trepool[i];
        tre->dma_sig = sig;
        tre->dev_name = dev_name;
        tre->callback = callback;
        tre->data = data;
        tre->idx = i;
        tre->status = 0;
        tre->queued = 0;
        tre->err_code = 0;
        tre->err_info = 0;
        tre->lldev = lldev;
        tre_local = &tre->tre_local[0];
        tre_local[HIDMA_TRE_CFG_IDX] = (lldev->chidx & 0xFF) << 8;
        tre_local[HIDMA_TRE_CFG_IDX] |= BIT(16);        /* set IEOB */
        *tre_ch = i;
        if (callback)
                callback(data);
        return 0;
}

/*
 * Multiple TREs may be queued and waiting in the pending queue.
 */
static void hidma_ll_tre_complete(struct tasklet_struct *t)
{
        struct hidma_lldev *lldev = from_tasklet(lldev, t, task);
        struct hidma_tre *tre;

        while (kfifo_out(&lldev->handoff_fifo, &tre, 1)) {
                /* call the user if it has been read by the hardware */
                if (tre->callback)
                        tre->callback(tre->data);
        }
}

static int hidma_post_completed(struct hidma_lldev *lldev, u8 err_info,
                                u8 err_code)
{
        struct hidma_tre *tre;
        unsigned long flags;
        u32 tre_iterator;

        spin_lock_irqsave(&lldev->lock, flags);

        tre_iterator = lldev->tre_processed_off;
        tre = lldev->pending_tre_list[tre_iterator / HIDMA_TRE_SIZE];
        if (!tre) {
                spin_unlock_irqrestore(&lldev->lock, flags);
                dev_warn(lldev->dev, "tre_index [%d] and tre out of sync\n",
                         tre_iterator / HIDMA_TRE_SIZE);
                return -EINVAL;
        }
        lldev->pending_tre_list[tre->tre_index] = NULL;

        /*
         * Keep track of pending TREs that SW is expecting to receive
         * from HW. We got one now. Decrement our counter.
         */
        if (atomic_dec_return(&lldev->pending_tre_count) < 0) {
                dev_warn(lldev->dev, "tre count mismatch on completion");
                atomic_set(&lldev->pending_tre_count, 0);
        }

        HIDMA_INCREMENT_ITERATOR(tre_iterator, HIDMA_TRE_SIZE,
                                 lldev->tre_ring_size);
        lldev->tre_processed_off = tre_iterator;
        spin_unlock_irqrestore(&lldev->lock, flags);

        tre->err_info = err_info;
        tre->err_code = err_code;
        tre->queued = 0;

        kfifo_put(&lldev->handoff_fifo, tre);
        tasklet_schedule(&lldev->task);

        return 0;
}

/*
 * Called to handle the interrupt for the channel.
 * Return a positive number if TRE or EVRE were consumed on this run.
 * Return a positive number if there are pending TREs or EVREs.
 * Return 0 if there is nothing to consume or no pending TREs/EVREs found.
 */
static int hidma_handle_tre_completion(struct hidma_lldev *lldev)
{
        u32 evre_ring_size = lldev->evre_ring_size;
        u32 err_info, err_code, evre_write_off;
        u32 evre_iterator;
        u32 num_completed = 0;

        evre_write_off = readl_relaxed(lldev->evca + HIDMA_EVCA_WRITE_PTR_REG);
        evre_iterator = lldev->evre_processed_off;

        if ((evre_write_off > evre_ring_size) ||
            (evre_write_off % HIDMA_EVRE_SIZE)) {
                dev_err(lldev->dev, "HW reports invalid EVRE write offset\n");
                return 0;
        }

        /*
         * By the time control reaches here the number of EVREs and TREs
         * may not match. Only consume the ones that hardware told us.
         */
        while ((evre_iterator != evre_write_off)) {
                u32 *current_evre = lldev->evre_ring + evre_iterator;
                u32 cfg;

                cfg = current_evre[HIDMA_EVRE_CFG_IDX];
                err_info = cfg >> HIDMA_EVRE_ERRINFO_BIT_POS;
                err_info &= HIDMA_EVRE_ERRINFO_MASK;
                err_code =
                    (cfg >> HIDMA_EVRE_CODE_BIT_POS) & HIDMA_EVRE_CODE_MASK;

                if (hidma_post_completed(lldev, err_info, err_code))
                        break;

                HIDMA_INCREMENT_ITERATOR(evre_iterator, HIDMA_EVRE_SIZE,
                                         evre_ring_size);

                /*
                 * Read the new event descriptor written by the HW.
                 * As we are processing the delivered events, other events
                 * get queued to the SW for processing.
                 */
                evre_write_off =
                    readl_relaxed(lldev->evca + HIDMA_EVCA_WRITE_PTR_REG);
                num_completed++;

                /*
                 * An error interrupt might have arrived while we are processing
                 * the completed interrupt.
                 */
                if (!hidma_ll_isenabled(lldev))
                        break;
        }

        if (num_completed) {
                u32 evre_read_off = (lldev->evre_processed_off +
                                     HIDMA_EVRE_SIZE * num_completed);
                evre_read_off = evre_read_off % evre_ring_size;
                writel(evre_read_off, lldev->evca + HIDMA_EVCA_DOORBELL_REG);

                /* record the last processed tre offset */
                lldev->evre_processed_off = evre_read_off;
        }

        return num_completed;
}

void hidma_cleanup_pending_tre(struct hidma_lldev *lldev, u8 err_info,
                               u8 err_code)
{
        while (atomic_read(&lldev->pending_tre_count)) {
                if (hidma_post_completed(lldev, err_info, err_code))
                        break;
        }
}

static int hidma_ll_reset(struct hidma_lldev *lldev)
{
        u32 val;
        int ret;

        val = readl(lldev->trca + HIDMA_TRCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_RESET << 16;
        writel(val, lldev->trca + HIDMA_TRCA_CTRLSTS_REG);

        /*
         * Delay 10ms after reset to allow DMA logic to quiesce.
         * Do a polled read up to 1ms and 10ms maximum.
         */
        ret = readl_poll_timeout(lldev->trca + HIDMA_TRCA_CTRLSTS_REG, val,
                                 HIDMA_CH_STATE(val) == HIDMA_CH_DISABLED,
                                 1000, 10000);
        if (ret) {
                dev_err(lldev->dev, "transfer channel did not reset\n");
                return ret;
        }

        val = readl(lldev->evca + HIDMA_EVCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_RESET << 16;
        writel(val, lldev->evca + HIDMA_EVCA_CTRLSTS_REG);

        /*
         * Delay 10ms after reset to allow DMA logic to quiesce.
         * Do a polled read up to 1ms and 10ms maximum.
         */
        ret = readl_poll_timeout(lldev->evca + HIDMA_EVCA_CTRLSTS_REG, val,
                                 HIDMA_CH_STATE(val) == HIDMA_CH_DISABLED,
                                 1000, 10000);
        if (ret)
                return ret;

        lldev->trch_state = HIDMA_CH_DISABLED;
        lldev->evch_state = HIDMA_CH_DISABLED;
        return 0;
}

/*
 * The interrupt handler for HIDMA will try to consume as many pending
 * EVRE from the event queue as possible. Each EVRE has an associated
 * TRE that holds the user interface parameters. EVRE reports the
 * result of the transaction. Hardware guarantees ordering between EVREs
 * and TREs. We use last processed offset to figure out which TRE is
 * associated with which EVRE. If two TREs are consumed by HW, the EVREs
 * are in order in the event ring.
 *
 * This handler will do a one pass for consuming EVREs. Other EVREs may
 * be delivered while we are working. It will try to consume incoming
 * EVREs one more time and return.
 *
 * For unprocessed EVREs, hardware will trigger another interrupt until
 * all the interrupt bits are cleared.
 *
 * Hardware guarantees that by the time interrupt is observed, all data
 * transactions in flight are delivered to their respective places and
 * are visible to the CPU.
 *
 * On demand paging for IOMMU is only supported for PCIe via PRI
 * (Page Request Interface) not for HIDMA. All other hardware instances
 * including HIDMA work on pinned DMA addresses.
 *
 * HIDMA is not aware of IOMMU presence since it follows the DMA API. All
 * IOMMU latency will be built into the data movement time. By the time
 * interrupt happens, IOMMU lookups + data movement has already taken place.
 *
 * While the first read in a typical PCI endpoint ISR flushes all outstanding
 * requests traditionally to the destination, this concept does not apply
 * here for this HW.
 */
static void hidma_ll_int_handler_internal(struct hidma_lldev *lldev, int cause)
{
        unsigned long irqflags;

        if (cause & HIDMA_ERR_INT_MASK) {
                dev_err(lldev->dev, "error 0x%x, disabling...\n",
                                cause);

                /* Clear out pending interrupts */
                writel(cause, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);

                /* No further submissions. */
                hidma_ll_disable(lldev);

                /* Driver completes the txn and intimates the client.*/
                hidma_cleanup_pending_tre(lldev, 0xFF,
                                          HIDMA_EVRE_STATUS_ERROR);

                return;
        }

        spin_lock_irqsave(&lldev->lock, irqflags);
        writel_relaxed(cause, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);
        spin_unlock_irqrestore(&lldev->lock, irqflags);

        /*
         * Fine tuned for this HW...
         *
         * This ISR has been designed for this particular hardware. Relaxed
         * read and write accessors are used for performance reasons due to
         * interrupt delivery guarantees. Do not copy this code blindly and
         * expect that to work.
         *
         * Try to consume as many EVREs as possible.
         */
        hidma_handle_tre_completion(lldev);
}

irqreturn_t hidma_ll_inthandler(int chirq, void *arg)
{
        struct hidma_lldev *lldev = arg;
        u32 status;
        u32 enable;
        u32 cause;

        status = readl_relaxed(lldev->evca + HIDMA_EVCA_IRQ_STAT_REG);
        enable = readl_relaxed(lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
        cause = status & enable;

        while (cause) {
                hidma_ll_int_handler_internal(lldev, cause);

                /*
                 * Another interrupt might have arrived while we are
                 * processing this one. Read the new cause.
                 */
                status = readl_relaxed(lldev->evca + HIDMA_EVCA_IRQ_STAT_REG);
                enable = readl_relaxed(lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
                cause = status & enable;
        }

        return IRQ_HANDLED;
}

irqreturn_t hidma_ll_inthandler_msi(int chirq, void *arg, int cause)
{
        struct hidma_lldev *lldev = arg;

        hidma_ll_int_handler_internal(lldev, cause);
        return IRQ_HANDLED;
}

int hidma_ll_enable(struct hidma_lldev *lldev)
{
        u32 val;
        int ret;

        val = readl(lldev->evca + HIDMA_EVCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_ENABLE << 16;
        writel(val, lldev->evca + HIDMA_EVCA_CTRLSTS_REG);

        ret = readl_poll_timeout(lldev->evca + HIDMA_EVCA_CTRLSTS_REG, val,
                                 hidma_is_chan_enabled(HIDMA_CH_STATE(val)),
                                 1000, 10000);
        if (ret) {
                dev_err(lldev->dev, "event channel did not get enabled\n");
                return ret;
        }

        val = readl(lldev->trca + HIDMA_TRCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_ENABLE << 16;
        writel(val, lldev->trca + HIDMA_TRCA_CTRLSTS_REG);

        ret = readl_poll_timeout(lldev->trca + HIDMA_TRCA_CTRLSTS_REG, val,
                                 hidma_is_chan_enabled(HIDMA_CH_STATE(val)),
                                 1000, 10000);
        if (ret) {
                dev_err(lldev->dev, "transfer channel did not get enabled\n");
                return ret;
        }

        lldev->trch_state = HIDMA_CH_ENABLED;
        lldev->evch_state = HIDMA_CH_ENABLED;

        /* enable irqs */
        writel(ENABLE_IRQS, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);

        return 0;
}

void hidma_ll_start(struct hidma_lldev *lldev)
{
        unsigned long irqflags;

        spin_lock_irqsave(&lldev->lock, irqflags);
        writel(lldev->tre_write_offset, lldev->trca + HIDMA_TRCA_DOORBELL_REG);
        spin_unlock_irqrestore(&lldev->lock, irqflags);
}

bool hidma_ll_isenabled(struct hidma_lldev *lldev)
{
        u32 val;

        val = readl(lldev->trca + HIDMA_TRCA_CTRLSTS_REG);
        lldev->trch_state = HIDMA_CH_STATE(val);
        val = readl(lldev->evca + HIDMA_EVCA_CTRLSTS_REG);
        lldev->evch_state = HIDMA_CH_STATE(val);

        /* both channels have to be enabled before calling this function */
        if (hidma_is_chan_enabled(lldev->trch_state) &&
            hidma_is_chan_enabled(lldev->evch_state))
                return true;

        return false;
}

void hidma_ll_queue_request(struct hidma_lldev *lldev, u32 tre_ch)
{
        struct hidma_tre *tre;
        unsigned long flags;

        tre = &lldev->trepool[tre_ch];

        /* copy the TRE into its location in the TRE ring */
        spin_lock_irqsave(&lldev->lock, flags);
        tre->tre_index = lldev->tre_write_offset / HIDMA_TRE_SIZE;
        lldev->pending_tre_list[tre->tre_index] = tre;
        memcpy(lldev->tre_ring + lldev->tre_write_offset,
                        &tre->tre_local[0], HIDMA_TRE_SIZE);
        tre->err_code = 0;
        tre->err_info = 0;
        tre->queued = 1;
        atomic_inc(&lldev->pending_tre_count);
        lldev->tre_write_offset = (lldev->tre_write_offset + HIDMA_TRE_SIZE)
                                        % lldev->tre_ring_size;
        spin_unlock_irqrestore(&lldev->lock, flags);
}

/*
 * Note that even though we stop this channel if there is a pending transaction
 * in flight it will complete and follow the callback. This request will
 * prevent further requests to be made.
 */
int hidma_ll_disable(struct hidma_lldev *lldev)
{
        u32 val;
        int ret;

        /* The channel needs to be in working state */
        if (!hidma_ll_isenabled(lldev))
                return 0;

        val = readl(lldev->trca + HIDMA_TRCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_SUSPEND << 16;
        writel(val, lldev->trca + HIDMA_TRCA_CTRLSTS_REG);

        /*
         * Start the wait right after the suspend is confirmed.
         * Do a polled read up to 1ms and 10ms maximum.
         */
        ret = readl_poll_timeout(lldev->trca + HIDMA_TRCA_CTRLSTS_REG, val,
                                 HIDMA_CH_STATE(val) == HIDMA_CH_SUSPENDED,
                                 1000, 10000);
        if (ret)
                return ret;

        val = readl(lldev->evca + HIDMA_EVCA_CTRLSTS_REG);
        val &= ~(HIDMA_CH_CONTROL_MASK << 16);
        val |= HIDMA_CH_SUSPEND << 16;
        writel(val, lldev->evca + HIDMA_EVCA_CTRLSTS_REG);

        /*
         * Start the wait right after the suspend is confirmed
         * Delay up to 10ms after reset to allow DMA logic to quiesce.
         */
        ret = readl_poll_timeout(lldev->evca + HIDMA_EVCA_CTRLSTS_REG, val,
                                 HIDMA_CH_STATE(val) == HIDMA_CH_SUSPENDED,
                                 1000, 10000);
        if (ret)
                return ret;

        lldev->trch_state = HIDMA_CH_SUSPENDED;
        lldev->evch_state = HIDMA_CH_SUSPENDED;

        /* disable interrupts */
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
        return 0;
}

void hidma_ll_set_transfer_params(struct hidma_lldev *lldev, u32 tre_ch,
                                  dma_addr_t src, dma_addr_t dest, u32 len,
                                  u32 flags, u32 txntype)
{
        struct hidma_tre *tre;
        u32 *tre_local;

        if (tre_ch >= lldev->nr_tres) {
                dev_err(lldev->dev, "invalid TRE number in transfer params:%d",
                        tre_ch);
                return;
        }

        tre = &lldev->trepool[tre_ch];
        if (atomic_read(&tre->allocated) != true) {
                dev_err(lldev->dev, "trying to set params on an unused TRE:%d",
                        tre_ch);
                return;
        }

        tre_local = &tre->tre_local[0];
        tre_local[HIDMA_TRE_CFG_IDX] &= ~GENMASK(7, 0);
        tre_local[HIDMA_TRE_CFG_IDX] |= txntype;
        tre_local[HIDMA_TRE_LEN_IDX] = len;
        tre_local[HIDMA_TRE_SRC_LOW_IDX] = lower_32_bits(src);
        tre_local[HIDMA_TRE_SRC_HI_IDX] = upper_32_bits(src);
        tre_local[HIDMA_TRE_DEST_LOW_IDX] = lower_32_bits(dest);
        tre_local[HIDMA_TRE_DEST_HI_IDX] = upper_32_bits(dest);
        tre->int_flags = flags;
}

/*
 * Called during initialization and after an error condition
 * to restore hardware state.
 */
int hidma_ll_setup(struct hidma_lldev *lldev)
{
        int rc;
        u64 addr;
        u32 val;
        u32 nr_tres = lldev->nr_tres;

        atomic_set(&lldev->pending_tre_count, 0);
        lldev->tre_processed_off = 0;
        lldev->evre_processed_off = 0;
        lldev->tre_write_offset = 0;

        /* disable interrupts */
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);

        /* clear all pending interrupts */
        val = readl(lldev->evca + HIDMA_EVCA_IRQ_STAT_REG);
        writel(val, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);

        rc = hidma_ll_reset(lldev);
        if (rc)
                return rc;

        /*
         * Clear all pending interrupts again.
         * Otherwise, we observe reset complete interrupts.
         */
        val = readl(lldev->evca + HIDMA_EVCA_IRQ_STAT_REG);
        writel(val, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);

        /* disable interrupts again after reset */
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);

        addr = lldev->tre_dma;
        writel(lower_32_bits(addr), lldev->trca + HIDMA_TRCA_RING_LOW_REG);
        writel(upper_32_bits(addr), lldev->trca + HIDMA_TRCA_RING_HIGH_REG);
        writel(lldev->tre_ring_size, lldev->trca + HIDMA_TRCA_RING_LEN_REG);

        addr = lldev->evre_dma;
        writel(lower_32_bits(addr), lldev->evca + HIDMA_EVCA_RING_LOW_REG);
        writel(upper_32_bits(addr), lldev->evca + HIDMA_EVCA_RING_HIGH_REG);
        writel(HIDMA_EVRE_SIZE * nr_tres,
                        lldev->evca + HIDMA_EVCA_RING_LEN_REG);

        /* configure interrupts */
        hidma_ll_setup_irq(lldev, lldev->msi_support);

        rc = hidma_ll_enable(lldev);
        if (rc)
                return rc;

        return rc;
}

void hidma_ll_setup_irq(struct hidma_lldev *lldev, bool msi)
{
        u32 val;

        lldev->msi_support = msi;

        /* disable interrupts again after reset */
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);

        /* support IRQ by default */
        val = readl(lldev->evca + HIDMA_EVCA_INTCTRL_REG);
        val &= ~0xF;
        if (!lldev->msi_support)
                val = val | 0x1;
        writel(val, lldev->evca + HIDMA_EVCA_INTCTRL_REG);

        /* clear all pending interrupts and enable them */
        writel(ENABLE_IRQS, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);
        writel(ENABLE_IRQS, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
}

struct hidma_lldev *hidma_ll_init(struct device *dev, u32 nr_tres,
                                  void __iomem *trca, void __iomem *evca,
                                  u8 chidx)
{
        u32 required_bytes;
        struct hidma_lldev *lldev;
        int rc;
        size_t sz;

        if (!trca || !evca || !dev || !nr_tres)
                return NULL;

        /* need at least four TREs */
        if (nr_tres < 4)
                return NULL;

        /* need an extra space */
        nr_tres += 1;

        lldev = devm_kzalloc(dev, sizeof(struct hidma_lldev), GFP_KERNEL);
        if (!lldev)
                return NULL;

        lldev->evca = evca;
        lldev->trca = trca;
        lldev->dev = dev;
        sz = sizeof(struct hidma_tre);
        lldev->trepool = devm_kcalloc(lldev->dev, nr_tres, sz, GFP_KERNEL);
        if (!lldev->trepool)
                return NULL;

        required_bytes = sizeof(lldev->pending_tre_list[0]);
        lldev->pending_tre_list = devm_kcalloc(dev, nr_tres, required_bytes,
                                               GFP_KERNEL);
        if (!lldev->pending_tre_list)
                return NULL;

        sz = (HIDMA_TRE_SIZE + 1) * nr_tres;
        lldev->tre_ring = dmam_alloc_coherent(dev, sz, &lldev->tre_dma,
                                              GFP_KERNEL);
        if (!lldev->tre_ring)
                return NULL;

        lldev->tre_ring_size = HIDMA_TRE_SIZE * nr_tres;
        lldev->nr_tres = nr_tres;

        /* the TRE ring has to be TRE_SIZE aligned */
        if (!IS_ALIGNED(lldev->tre_dma, HIDMA_TRE_SIZE)) {
                u8 tre_ring_shift;

                tre_ring_shift = lldev->tre_dma % HIDMA_TRE_SIZE;
                tre_ring_shift = HIDMA_TRE_SIZE - tre_ring_shift;
                lldev->tre_dma += tre_ring_shift;
                lldev->tre_ring += tre_ring_shift;
        }

        sz = (HIDMA_EVRE_SIZE + 1) * nr_tres;
        lldev->evre_ring = dmam_alloc_coherent(dev, sz, &lldev->evre_dma,
                                               GFP_KERNEL);
        if (!lldev->evre_ring)
                return NULL;

        lldev->evre_ring_size = HIDMA_EVRE_SIZE * nr_tres;

        /* the EVRE ring has to be EVRE_SIZE aligned */
        if (!IS_ALIGNED(lldev->evre_dma, HIDMA_EVRE_SIZE)) {
                u8 evre_ring_shift;

                evre_ring_shift = lldev->evre_dma % HIDMA_EVRE_SIZE;
                evre_ring_shift = HIDMA_EVRE_SIZE - evre_ring_shift;
                lldev->evre_dma += evre_ring_shift;
                lldev->evre_ring += evre_ring_shift;
        }
        lldev->nr_tres = nr_tres;
        lldev->chidx = chidx;

        sz = nr_tres * sizeof(struct hidma_tre *);
        rc = kfifo_alloc(&lldev->handoff_fifo, sz, GFP_KERNEL);
        if (rc)
                return NULL;

        rc = hidma_ll_setup(lldev);
        if (rc)
                return NULL;

        spin_lock_init(&lldev->lock);
        tasklet_setup(&lldev->task, hidma_ll_tre_complete);
        lldev->initialized = 1;
        writel(ENABLE_IRQS, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
        return lldev;
}

int hidma_ll_uninit(struct hidma_lldev *lldev)
{
        u32 required_bytes;
        int rc = 0;
        u32 val;

        if (!lldev)
                return -ENODEV;

        if (!lldev->initialized)
                return 0;

        lldev->initialized = 0;

        required_bytes = sizeof(struct hidma_tre) * lldev->nr_tres;
        tasklet_kill(&lldev->task);
        memset(lldev->trepool, 0, required_bytes);
        lldev->trepool = NULL;
        atomic_set(&lldev->pending_tre_count, 0);
        lldev->tre_write_offset = 0;

        rc = hidma_ll_reset(lldev);

        /*
         * Clear all pending interrupts again.
         * Otherwise, we observe reset complete interrupts.
         */
        val = readl(lldev->evca + HIDMA_EVCA_IRQ_STAT_REG);
        writel(val, lldev->evca + HIDMA_EVCA_IRQ_CLR_REG);
        writel(0, lldev->evca + HIDMA_EVCA_IRQ_EN_REG);
        return rc;
}

enum dma_status hidma_ll_status(struct hidma_lldev *lldev, u32 tre_ch)
{
        enum dma_status ret = DMA_ERROR;
        struct hidma_tre *tre;
        unsigned long flags;
        u8 err_code;

        spin_lock_irqsave(&lldev->lock, flags);

        tre = &lldev->trepool[tre_ch];
        err_code = tre->err_code;

        if (err_code & HIDMA_EVRE_STATUS_COMPLETE)
                ret = DMA_COMPLETE;
        else if (err_code & HIDMA_EVRE_STATUS_ERROR)
                ret = DMA_ERROR;
        else
                ret = DMA_IN_PROGRESS;
        spin_unlock_irqrestore(&lldev->lock, flags);

        return ret;
}