// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
 *
 */

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/mhi.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include "internal.h"

int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl,
                              void __iomem *base, u32 offset, u32 *out)
{
        return mhi_cntrl->read_reg(mhi_cntrl, base + offset, out);
}

int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
                                    void __iomem *base, u32 offset,
                                    u32 mask, u32 shift, u32 *out)
{
        u32 tmp;
        int ret;

        ret = mhi_read_reg(mhi_cntrl, base, offset, &tmp);
        if (ret)
                return ret;

        *out = (tmp & mask) >> shift;

        return 0;
}

int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
                                    void __iomem *base, u32 offset,
                                    u32 mask, u32 shift, u32 val, u32 delayus)
{
        int ret;
        u32 out, retry = (mhi_cntrl->timeout_ms * 1000) / delayus;

        while (retry--) {
                ret = mhi_read_reg_field(mhi_cntrl, base, offset, mask, shift,
                                         &out);
                if (ret)
                        return ret;

                if (out == val)
                        return 0;

                fsleep(delayus);
        }

        return -ETIMEDOUT;
}

void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
                   u32 offset, u32 val)
{
        mhi_cntrl->write_reg(mhi_cntrl, base + offset, val);
}

void mhi_write_reg_field(struct mhi_controller *mhi_cntrl, void __iomem *base,
                         u32 offset, u32 mask, u32 shift, u32 val)
{
        int ret;
        u32 tmp;

        ret = mhi_read_reg(mhi_cntrl, base, offset, &tmp);
        if (ret)
                return;

        tmp &= ~mask;
        tmp |= (val << shift);
        mhi_write_reg(mhi_cntrl, base, offset, tmp);
}

void mhi_write_db(struct mhi_controller *mhi_cntrl, void __iomem *db_addr,
                  dma_addr_t db_val)
{
        mhi_write_reg(mhi_cntrl, db_addr, 4, upper_32_bits(db_val));
        mhi_write_reg(mhi_cntrl, db_addr, 0, lower_32_bits(db_val));
}

void mhi_db_brstmode(struct mhi_controller *mhi_cntrl,
                     struct db_cfg *db_cfg,
                     void __iomem *db_addr,
                     dma_addr_t db_val)
{
        if (db_cfg->db_mode) {
                db_cfg->db_val = db_val;
                mhi_write_db(mhi_cntrl, db_addr, db_val);
                db_cfg->db_mode = 0;
        }
}

void mhi_db_brstmode_disable(struct mhi_controller *mhi_cntrl,
                             struct db_cfg *db_cfg,
                             void __iomem *db_addr,
                             dma_addr_t db_val)
{
        db_cfg->db_val = db_val;
        mhi_write_db(mhi_cntrl, db_addr, db_val);
}

void mhi_ring_er_db(struct mhi_event *mhi_event)
{
        struct mhi_ring *ring = &mhi_event->ring;

        mhi_event->db_cfg.process_db(mhi_event->mhi_cntrl, &mhi_event->db_cfg,
                                     ring->db_addr, *ring->ctxt_wp);
}

void mhi_ring_cmd_db(struct mhi_controller *mhi_cntrl, struct mhi_cmd *mhi_cmd)
{
        dma_addr_t db;
        struct mhi_ring *ring = &mhi_cmd->ring;

        db = ring->iommu_base + (ring->wp - ring->base);
        *ring->ctxt_wp = db;
        mhi_write_db(mhi_cntrl, ring->db_addr, db);
}

void mhi_ring_chan_db(struct mhi_controller *mhi_cntrl,
                      struct mhi_chan *mhi_chan)
{
        struct mhi_ring *ring = &mhi_chan->tre_ring;
        dma_addr_t db;

        db = ring->iommu_base + (ring->wp - ring->base);

        /*
         * Writes to the new ring element must be visible to the hardware
         * before letting h/w know there is new element to fetch.
         */
        dma_wmb();
        *ring->ctxt_wp = db;

        mhi_chan->db_cfg.process_db(mhi_cntrl, &mhi_chan->db_cfg,
                                    ring->db_addr, db);
}

enum mhi_ee_type mhi_get_exec_env(struct mhi_controller *mhi_cntrl)
{
        u32 exec;
        int ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_EXECENV, &exec);

        return (ret) ? MHI_EE_MAX : exec;
}
EXPORT_SYMBOL_GPL(mhi_get_exec_env);

enum mhi_state mhi_get_mhi_state(struct mhi_controller *mhi_cntrl)
{
        u32 state;
        int ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MHISTATUS,
                                     MHISTATUS_MHISTATE_MASK,
                                     MHISTATUS_MHISTATE_SHIFT, &state);
        return ret ? MHI_STATE_MAX : state;
}
EXPORT_SYMBOL_GPL(mhi_get_mhi_state);

void mhi_soc_reset(struct mhi_controller *mhi_cntrl)
{
        if (mhi_cntrl->reset) {
                mhi_cntrl->reset(mhi_cntrl);
                return;
        }

        /* Generic MHI SoC reset */
        mhi_write_reg(mhi_cntrl, mhi_cntrl->regs, MHI_SOC_RESET_REQ_OFFSET,
                      MHI_SOC_RESET_REQ);
}
EXPORT_SYMBOL_GPL(mhi_soc_reset);

int mhi_map_single_no_bb(struct mhi_controller *mhi_cntrl,
                         struct mhi_buf_info *buf_info)
{
        buf_info->p_addr = dma_map_single(mhi_cntrl->cntrl_dev,
                                          buf_info->v_addr, buf_info->len,
                                          buf_info->dir);
        if (dma_mapping_error(mhi_cntrl->cntrl_dev, buf_info->p_addr))
                return -ENOMEM;

        return 0;
}

int mhi_map_single_use_bb(struct mhi_controller *mhi_cntrl,
                          struct mhi_buf_info *buf_info)
{
        void *buf = dma_alloc_coherent(mhi_cntrl->cntrl_dev, buf_info->len,
                                       &buf_info->p_addr, GFP_ATOMIC);

        if (!buf)
                return -ENOMEM;

        if (buf_info->dir == DMA_TO_DEVICE)
                memcpy(buf, buf_info->v_addr, buf_info->len);

        buf_info->bb_addr = buf;

        return 0;
}

void mhi_unmap_single_no_bb(struct mhi_controller *mhi_cntrl,
                            struct mhi_buf_info *buf_info)
{
        dma_unmap_single(mhi_cntrl->cntrl_dev, buf_info->p_addr, buf_info->len,
                         buf_info->dir);
}

void mhi_unmap_single_use_bb(struct mhi_controller *mhi_cntrl,
                             struct mhi_buf_info *buf_info)
{
        if (buf_info->dir == DMA_FROM_DEVICE)
                memcpy(buf_info->v_addr, buf_info->bb_addr, buf_info->len);

        dma_free_coherent(mhi_cntrl->cntrl_dev, buf_info->len,
                          buf_info->bb_addr, buf_info->p_addr);
}

static int get_nr_avail_ring_elements(struct mhi_controller *mhi_cntrl,
                                      struct mhi_ring *ring)
{
        int nr_el;

        if (ring->wp < ring->rp) {
                nr_el = ((ring->rp - ring->wp) / ring->el_size) - 1;
        } else {
                nr_el = (ring->rp - ring->base) / ring->el_size;
                nr_el += ((ring->base + ring->len - ring->wp) /
                          ring->el_size) - 1;
        }

        return nr_el;
}

static void *mhi_to_virtual(struct mhi_ring *ring, dma_addr_t addr)
{
        return (addr - ring->iommu_base) + ring->base;
}

static void mhi_add_ring_element(struct mhi_controller *mhi_cntrl,
                                 struct mhi_ring *ring)
{
        ring->wp += ring->el_size;
        if (ring->wp >= (ring->base + ring->len))
                ring->wp = ring->base;
        /* smp update */
        smp_wmb();
}

static void mhi_del_ring_element(struct mhi_controller *mhi_cntrl,
                                 struct mhi_ring *ring)
{
        ring->rp += ring->el_size;
        if (ring->rp >= (ring->base + ring->len))
                ring->rp = ring->base;
        /* smp update */
        smp_wmb();
}

static bool is_valid_ring_ptr(struct mhi_ring *ring, dma_addr_t addr)
{
        return addr >= ring->iommu_base && addr < ring->iommu_base + ring->len;
}

int mhi_destroy_device(struct device *dev, void *data)
{
        struct mhi_chan *ul_chan, *dl_chan;
        struct mhi_device *mhi_dev;
        struct mhi_controller *mhi_cntrl;
        enum mhi_ee_type ee = MHI_EE_MAX;

        if (dev->bus != &mhi_bus_type)
                return 0;

        mhi_dev = to_mhi_device(dev);
        mhi_cntrl = mhi_dev->mhi_cntrl;

        /* Only destroy virtual devices thats attached to bus */
        if (mhi_dev->dev_type == MHI_DEVICE_CONTROLLER)
                return 0;

        ul_chan = mhi_dev->ul_chan;
        dl_chan = mhi_dev->dl_chan;

        /*
         * If execution environment is specified, remove only those devices that
         * started in them based on ee_mask for the channels as we move on to a
         * different execution environment
         */
        if (data)
                ee = *(enum mhi_ee_type *)data;

        /*
         * For the suspend and resume case, this function will get called
         * without mhi_unregister_controller(). Hence, we need to drop the
         * references to mhi_dev created for ul and dl channels. We can
         * be sure that there will be no instances of mhi_dev left after
         * this.
         */
        if (ul_chan) {
                if (ee != MHI_EE_MAX && !(ul_chan->ee_mask & BIT(ee)))
                        return 0;

                put_device(&ul_chan->mhi_dev->dev);
        }

        if (dl_chan) {
                if (ee != MHI_EE_MAX && !(dl_chan->ee_mask & BIT(ee)))
                        return 0;

                put_device(&dl_chan->mhi_dev->dev);
        }

        dev_dbg(&mhi_cntrl->mhi_dev->dev, "destroy device for chan:%s\n",
                 mhi_dev->name);

        /* Notify the client and remove the device from MHI bus */
        device_del(dev);
        put_device(dev);

        return 0;
}

int mhi_get_free_desc_count(struct mhi_device *mhi_dev,
                                enum dma_data_direction dir)
{
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ?
                mhi_dev->ul_chan : mhi_dev->dl_chan;
        struct mhi_ring *tre_ring = &mhi_chan->tre_ring;

        return get_nr_avail_ring_elements(mhi_cntrl, tre_ring);
}
EXPORT_SYMBOL_GPL(mhi_get_free_desc_count);

void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason)
{
        struct mhi_driver *mhi_drv;

        if (!mhi_dev->dev.driver)
                return;

        mhi_drv = to_mhi_driver(mhi_dev->dev.driver);

        if (mhi_drv->status_cb)
                mhi_drv->status_cb(mhi_dev, cb_reason);
}
EXPORT_SYMBOL_GPL(mhi_notify);

/* Bind MHI channels to MHI devices */
void mhi_create_devices(struct mhi_controller *mhi_cntrl)
{
        struct mhi_chan *mhi_chan;
        struct mhi_device *mhi_dev;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        int i, ret;

        mhi_chan = mhi_cntrl->mhi_chan;
        for (i = 0; i < mhi_cntrl->max_chan; i++, mhi_chan++) {
                if (!mhi_chan->configured || mhi_chan->mhi_dev ||
                    !(mhi_chan->ee_mask & BIT(mhi_cntrl->ee)))
                        continue;
                mhi_dev = mhi_alloc_device(mhi_cntrl);
                if (IS_ERR(mhi_dev))
                        return;

                mhi_dev->dev_type = MHI_DEVICE_XFER;
                switch (mhi_chan->dir) {
                case DMA_TO_DEVICE:
                        mhi_dev->ul_chan = mhi_chan;
                        mhi_dev->ul_chan_id = mhi_chan->chan;
                        break;
                case DMA_FROM_DEVICE:
                        /* We use dl_chan as offload channels */
                        mhi_dev->dl_chan = mhi_chan;
                        mhi_dev->dl_chan_id = mhi_chan->chan;
                        break;
                default:
                        dev_err(dev, "Direction not supported\n");
                        put_device(&mhi_dev->dev);
                        return;
                }

                get_device(&mhi_dev->dev);
                mhi_chan->mhi_dev = mhi_dev;

                /* Check next channel if it matches */
                if ((i + 1) < mhi_cntrl->max_chan && mhi_chan[1].configured) {
                        if (!strcmp(mhi_chan[1].name, mhi_chan->name)) {
                                i++;
                                mhi_chan++;
                                if (mhi_chan->dir == DMA_TO_DEVICE) {
                                        mhi_dev->ul_chan = mhi_chan;
                                        mhi_dev->ul_chan_id = mhi_chan->chan;
                                } else {
                                        mhi_dev->dl_chan = mhi_chan;
                                        mhi_dev->dl_chan_id = mhi_chan->chan;
                                }
                                get_device(&mhi_dev->dev);
                                mhi_chan->mhi_dev = mhi_dev;
                        }
                }

                /* Channel name is same for both UL and DL */
                mhi_dev->name = mhi_chan->name;
                dev_set_name(&mhi_dev->dev, "%s_%s",
                             dev_name(&mhi_cntrl->mhi_dev->dev),
                             mhi_dev->name);

                /* Init wakeup source if available */
                if (mhi_dev->dl_chan && mhi_dev->dl_chan->wake_capable)
                        device_init_wakeup(&mhi_dev->dev, true);

                ret = device_add(&mhi_dev->dev);
                if (ret)
                        put_device(&mhi_dev->dev);
        }
}

irqreturn_t mhi_irq_handler(int irq_number, void *dev)
{
        struct mhi_event *mhi_event = dev;
        struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
        struct mhi_event_ctxt *er_ctxt =
                &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
        struct mhi_ring *ev_ring = &mhi_event->ring;
        dma_addr_t ptr = er_ctxt->rp;
        void *dev_rp;

        if (!is_valid_ring_ptr(ev_ring, ptr)) {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Event ring rp points outside of the event ring\n");
                return IRQ_HANDLED;
        }

        dev_rp = mhi_to_virtual(ev_ring, ptr);

        /* Only proceed if event ring has pending events */
        if (ev_ring->rp == dev_rp)
                return IRQ_HANDLED;

        /* For client managed event ring, notify pending data */
        if (mhi_event->cl_manage) {
                struct mhi_chan *mhi_chan = mhi_event->mhi_chan;
                struct mhi_device *mhi_dev = mhi_chan->mhi_dev;

                if (mhi_dev)
                        mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
        } else {
                tasklet_schedule(&mhi_event->task);
        }

        return IRQ_HANDLED;
}

irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
{
        struct mhi_controller *mhi_cntrl = priv;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        enum mhi_state state;
        enum mhi_pm_state pm_state = 0;
        enum mhi_ee_type ee;

        write_lock_irq(&mhi_cntrl->pm_lock);
        if (!MHI_REG_ACCESS_VALID(mhi_cntrl->pm_state)) {
                write_unlock_irq(&mhi_cntrl->pm_lock);
                goto exit_intvec;
        }

        state = mhi_get_mhi_state(mhi_cntrl);
        ee = mhi_get_exec_env(mhi_cntrl);
        dev_dbg(dev, "local ee: %s state: %s device ee: %s state: %s\n",
                TO_MHI_EXEC_STR(mhi_cntrl->ee),
                TO_MHI_STATE_STR(mhi_cntrl->dev_state),
                TO_MHI_EXEC_STR(ee), TO_MHI_STATE_STR(state));

        if (state == MHI_STATE_SYS_ERR) {
                dev_dbg(dev, "System error detected\n");
                pm_state = mhi_tryset_pm_state(mhi_cntrl,
                                               MHI_PM_SYS_ERR_DETECT);
        }
        write_unlock_irq(&mhi_cntrl->pm_lock);

        if (pm_state != MHI_PM_SYS_ERR_DETECT || ee == mhi_cntrl->ee)
                goto exit_intvec;

        switch (ee) {
        case MHI_EE_RDDM:
                /* proceed if power down is not already in progress */
                if (mhi_cntrl->rddm_image && mhi_is_active(mhi_cntrl)) {
                        mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_EE_RDDM);
                        mhi_cntrl->ee = ee;
                        wake_up_all(&mhi_cntrl->state_event);
                }
                break;
        case MHI_EE_PBL:
        case MHI_EE_EDL:
        case MHI_EE_PTHRU:
                mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_FATAL_ERROR);
                mhi_cntrl->ee = ee;
                wake_up_all(&mhi_cntrl->state_event);
                mhi_pm_sys_err_handler(mhi_cntrl);
                break;
        default:
                wake_up_all(&mhi_cntrl->state_event);
                mhi_pm_sys_err_handler(mhi_cntrl);
                break;
        }

exit_intvec:

        return IRQ_HANDLED;
}

irqreturn_t mhi_intvec_handler(int irq_number, void *dev)
{
        struct mhi_controller *mhi_cntrl = dev;

        /* Wake up events waiting for state change */
        wake_up_all(&mhi_cntrl->state_event);

        return IRQ_WAKE_THREAD;
}

static void mhi_recycle_ev_ring_element(struct mhi_controller *mhi_cntrl,
                                        struct mhi_ring *ring)
{
        dma_addr_t ctxt_wp;

        /* Update the WP */
        ring->wp += ring->el_size;
        ctxt_wp = *ring->ctxt_wp + ring->el_size;

        if (ring->wp >= (ring->base + ring->len)) {
                ring->wp = ring->base;
                ctxt_wp = ring->iommu_base;
        }

        *ring->ctxt_wp = ctxt_wp;

        /* Update the RP */
        ring->rp += ring->el_size;
        if (ring->rp >= (ring->base + ring->len))
                ring->rp = ring->base;

        /* Update to all cores */
        smp_wmb();
}

static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
                            struct mhi_tre *event,
                            struct mhi_chan *mhi_chan)
{
        struct mhi_ring *buf_ring, *tre_ring;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        struct mhi_result result;
        unsigned long flags = 0;
        u32 ev_code;

        ev_code = MHI_TRE_GET_EV_CODE(event);
        buf_ring = &mhi_chan->buf_ring;
        tre_ring = &mhi_chan->tre_ring;

        result.transaction_status = (ev_code == MHI_EV_CC_OVERFLOW) ?
                -EOVERFLOW : 0;

        /*
         * If it's a DB Event then we need to grab the lock
         * with preemption disabled and as a write because we
         * have to update db register and there are chances that
         * another thread could be doing the same.
         */
        if (ev_code >= MHI_EV_CC_OOB)
                write_lock_irqsave(&mhi_chan->lock, flags);
        else
                read_lock_bh(&mhi_chan->lock);

        if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
                goto end_process_tx_event;

        switch (ev_code) {
        case MHI_EV_CC_OVERFLOW:
        case MHI_EV_CC_EOB:
        case MHI_EV_CC_EOT:
        {
                dma_addr_t ptr = MHI_TRE_GET_EV_PTR(event);
                struct mhi_tre *local_rp, *ev_tre;
                void *dev_rp;
                struct mhi_buf_info *buf_info;
                u16 xfer_len;

                if (!is_valid_ring_ptr(tre_ring, ptr)) {
                        dev_err(&mhi_cntrl->mhi_dev->dev,
                                "Event element points outside of the tre ring\n");
                        break;
                }
                /* Get the TRB this event points to */
                ev_tre = mhi_to_virtual(tre_ring, ptr);

                dev_rp = ev_tre + 1;
                if (dev_rp >= (tre_ring->base + tre_ring->len))
                        dev_rp = tre_ring->base;

                result.dir = mhi_chan->dir;

                local_rp = tre_ring->rp;
                while (local_rp != dev_rp) {
                        buf_info = buf_ring->rp;
                        /* If it's the last TRE, get length from the event */
                        if (local_rp == ev_tre)
                                xfer_len = MHI_TRE_GET_EV_LEN(event);
                        else
                                xfer_len = buf_info->len;

                        /* Unmap if it's not pre-mapped by client */
                        if (likely(!buf_info->pre_mapped))
                                mhi_cntrl->unmap_single(mhi_cntrl, buf_info);

                        result.buf_addr = buf_info->cb_buf;

                        /* truncate to buf len if xfer_len is larger */
                        result.bytes_xferd =
                                min_t(u16, xfer_len, buf_info->len);
                        mhi_del_ring_element(mhi_cntrl, buf_ring);
                        mhi_del_ring_element(mhi_cntrl, tre_ring);
                        local_rp = tre_ring->rp;

                        /* notify client */
                        mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);

                        if (mhi_chan->dir == DMA_TO_DEVICE) {
                                atomic_dec(&mhi_cntrl->pending_pkts);
                                /* Release the reference got from mhi_queue() */
                                mhi_cntrl->runtime_put(mhi_cntrl);
                        }

                        /*
                         * Recycle the buffer if buffer is pre-allocated,
                         * if there is an error, not much we can do apart
                         * from dropping the packet
                         */
                        if (mhi_chan->pre_alloc) {
                                if (mhi_queue_buf(mhi_chan->mhi_dev,
                                                  mhi_chan->dir,
                                                  buf_info->cb_buf,
                                                  buf_info->len, MHI_EOT)) {
                                        dev_err(dev,
                                                "Error recycling buffer for chan:%d\n",
                                                mhi_chan->chan);
                                        kfree(buf_info->cb_buf);
                                }
                        }
                }
                break;
        } /* CC_EOT */
        case MHI_EV_CC_OOB:
        case MHI_EV_CC_DB_MODE:
        {
                unsigned long pm_lock_flags;

                mhi_chan->db_cfg.db_mode = 1;
                read_lock_irqsave(&mhi_cntrl->pm_lock, pm_lock_flags);
                if (tre_ring->wp != tre_ring->rp &&
                    MHI_DB_ACCESS_VALID(mhi_cntrl)) {
                        mhi_ring_chan_db(mhi_cntrl, mhi_chan);
                }
                read_unlock_irqrestore(&mhi_cntrl->pm_lock, pm_lock_flags);
                break;
        }
        case MHI_EV_CC_BAD_TRE:
        default:
                dev_err(dev, "Unknown event 0x%x\n", ev_code);
                break;
        } /* switch(MHI_EV_READ_CODE(EV_TRB_CODE,event)) */

end_process_tx_event:
        if (ev_code >= MHI_EV_CC_OOB)
                write_unlock_irqrestore(&mhi_chan->lock, flags);
        else
                read_unlock_bh(&mhi_chan->lock);

        return 0;
}

static int parse_rsc_event(struct mhi_controller *mhi_cntrl,
                           struct mhi_tre *event,
                           struct mhi_chan *mhi_chan)
{
        struct mhi_ring *buf_ring, *tre_ring;
        struct mhi_buf_info *buf_info;
        struct mhi_result result;
        int ev_code;
        u32 cookie; /* offset to local descriptor */
        u16 xfer_len;

        buf_ring = &mhi_chan->buf_ring;
        tre_ring = &mhi_chan->tre_ring;

        ev_code = MHI_TRE_GET_EV_CODE(event);
        cookie = MHI_TRE_GET_EV_COOKIE(event);
        xfer_len = MHI_TRE_GET_EV_LEN(event);

        /* Received out of bound cookie */
        WARN_ON(cookie >= buf_ring->len);

        buf_info = buf_ring->base + cookie;

        result.transaction_status = (ev_code == MHI_EV_CC_OVERFLOW) ?
                -EOVERFLOW : 0;

        /* truncate to buf len if xfer_len is larger */
        result.bytes_xferd = min_t(u16, xfer_len, buf_info->len);
        result.buf_addr = buf_info->cb_buf;
        result.dir = mhi_chan->dir;

        read_lock_bh(&mhi_chan->lock);

        if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
                goto end_process_rsc_event;

        WARN_ON(!buf_info->used);

        /* notify the client */
        mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);

        /*
         * Note: We're arbitrarily incrementing RP even though, completion
         * packet we processed might not be the same one, reason we can do this
         * is because device guaranteed to cache descriptors in order it
         * receive, so even though completion event is different we can re-use
         * all descriptors in between.
         * Example:
         * Transfer Ring has descriptors: A, B, C, D
         * Last descriptor host queue is D (WP) and first descriptor
         * host queue is A (RP).
         * The completion event we just serviced is descriptor C.
         * Then we can safely queue descriptors to replace A, B, and C
         * even though host did not receive any completions.
         */
        mhi_del_ring_element(mhi_cntrl, tre_ring);
        buf_info->used = false;

end_process_rsc_event:
        read_unlock_bh(&mhi_chan->lock);

        return 0;
}

static void mhi_process_cmd_completion(struct mhi_controller *mhi_cntrl,
                                       struct mhi_tre *tre)
{
        dma_addr_t ptr = MHI_TRE_GET_EV_PTR(tre);
        struct mhi_cmd *cmd_ring = &mhi_cntrl->mhi_cmd[PRIMARY_CMD_RING];
        struct mhi_ring *mhi_ring = &cmd_ring->ring;
        struct mhi_tre *cmd_pkt;
        struct mhi_chan *mhi_chan;
        u32 chan;

        if (!is_valid_ring_ptr(mhi_ring, ptr)) {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Event element points outside of the cmd ring\n");
                return;
        }

        cmd_pkt = mhi_to_virtual(mhi_ring, ptr);

        chan = MHI_TRE_GET_CMD_CHID(cmd_pkt);

        if (chan < mhi_cntrl->max_chan &&
            mhi_cntrl->mhi_chan[chan].configured) {
                mhi_chan = &mhi_cntrl->mhi_chan[chan];
                write_lock_bh(&mhi_chan->lock);
                mhi_chan->ccs = MHI_TRE_GET_EV_CODE(tre);
                complete(&mhi_chan->completion);
                write_unlock_bh(&mhi_chan->lock);
        } else {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Completion packet for invalid channel ID: %d\n", chan);
        }

        mhi_del_ring_element(mhi_cntrl, mhi_ring);
}

int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
                             struct mhi_event *mhi_event,
                             u32 event_quota)
{
        struct mhi_tre *dev_rp, *local_rp;
        struct mhi_ring *ev_ring = &mhi_event->ring;
        struct mhi_event_ctxt *er_ctxt =
                &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
        struct mhi_chan *mhi_chan;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        u32 chan;
        int count = 0;
        dma_addr_t ptr = er_ctxt->rp;

        /*
         * This is a quick check to avoid unnecessary event processing
         * in case MHI is already in error state, but it's still possible
         * to transition to error state while processing events
         */
        if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
                return -EIO;

        if (!is_valid_ring_ptr(ev_ring, ptr)) {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Event ring rp points outside of the event ring\n");
                return -EIO;
        }

        dev_rp = mhi_to_virtual(ev_ring, ptr);
        local_rp = ev_ring->rp;

        while (dev_rp != local_rp) {
                enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);

                switch (type) {
                case MHI_PKT_TYPE_BW_REQ_EVENT:
                {
                        struct mhi_link_info *link_info;

                        link_info = &mhi_cntrl->mhi_link_info;
                        write_lock_irq(&mhi_cntrl->pm_lock);
                        link_info->target_link_speed =
                                MHI_TRE_GET_EV_LINKSPEED(local_rp);
                        link_info->target_link_width =
                                MHI_TRE_GET_EV_LINKWIDTH(local_rp);
                        write_unlock_irq(&mhi_cntrl->pm_lock);
                        dev_dbg(dev, "Received BW_REQ event\n");
                        mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_BW_REQ);
                        break;
                }
                case MHI_PKT_TYPE_STATE_CHANGE_EVENT:
                {
                        enum mhi_state new_state;

                        new_state = MHI_TRE_GET_EV_STATE(local_rp);

                        dev_dbg(dev, "State change event to state: %s\n",
                                TO_MHI_STATE_STR(new_state));

                        switch (new_state) {
                        case MHI_STATE_M0:
                                mhi_pm_m0_transition(mhi_cntrl);
                                break;
                        case MHI_STATE_M1:
                                mhi_pm_m1_transition(mhi_cntrl);
                                break;
                        case MHI_STATE_M3:
                                mhi_pm_m3_transition(mhi_cntrl);
                                break;
                        case MHI_STATE_SYS_ERR:
                        {
                                enum mhi_pm_state pm_state;

                                dev_dbg(dev, "System error detected\n");
                                write_lock_irq(&mhi_cntrl->pm_lock);
                                pm_state = mhi_tryset_pm_state(mhi_cntrl,
                                                        MHI_PM_SYS_ERR_DETECT);
                                write_unlock_irq(&mhi_cntrl->pm_lock);
                                if (pm_state == MHI_PM_SYS_ERR_DETECT)
                                        mhi_pm_sys_err_handler(mhi_cntrl);
                                break;
                        }
                        default:
                                dev_err(dev, "Invalid state: %s\n",
                                        TO_MHI_STATE_STR(new_state));
                        }

                        break;
                }
                case MHI_PKT_TYPE_CMD_COMPLETION_EVENT:
                        mhi_process_cmd_completion(mhi_cntrl, local_rp);
                        break;
                case MHI_PKT_TYPE_EE_EVENT:
                {
                        enum dev_st_transition st = DEV_ST_TRANSITION_MAX;
                        enum mhi_ee_type event = MHI_TRE_GET_EV_EXECENV(local_rp);

                        dev_dbg(dev, "Received EE event: %s\n",
                                TO_MHI_EXEC_STR(event));
                        switch (event) {
                        case MHI_EE_SBL:
                                st = DEV_ST_TRANSITION_SBL;
                                break;
                        case MHI_EE_WFW:
                        case MHI_EE_AMSS:
                                st = DEV_ST_TRANSITION_MISSION_MODE;
                                break;
                        case MHI_EE_FP:
                                st = DEV_ST_TRANSITION_FP;
                                break;
                        case MHI_EE_RDDM:
                                mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_EE_RDDM);
                                write_lock_irq(&mhi_cntrl->pm_lock);
                                mhi_cntrl->ee = event;
                                write_unlock_irq(&mhi_cntrl->pm_lock);
                                wake_up_all(&mhi_cntrl->state_event);
                                break;
                        default:
                                dev_err(dev,
                                        "Unhandled EE event: 0x%x\n", type);
                        }
                        if (st != DEV_ST_TRANSITION_MAX)
                                mhi_queue_state_transition(mhi_cntrl, st);

                        break;
                }
                case MHI_PKT_TYPE_TX_EVENT:
                        chan = MHI_TRE_GET_EV_CHID(local_rp);

                        WARN_ON(chan >= mhi_cntrl->max_chan);

                        /*
                         * Only process the event ring elements whose channel
                         * ID is within the maximum supported range.
                         */
                        if (chan < mhi_cntrl->max_chan) {
                                mhi_chan = &mhi_cntrl->mhi_chan[chan];
                                if (!mhi_chan->configured)
                                        break;
                                parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
                                event_quota--;
                        }
                        break;
                default:
                        dev_err(dev, "Unhandled event type: %d\n", type);
                        break;
                }

                mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
                local_rp = ev_ring->rp;

                ptr = er_ctxt->rp;
                if (!is_valid_ring_ptr(ev_ring, ptr)) {
                        dev_err(&mhi_cntrl->mhi_dev->dev,
                                "Event ring rp points outside of the event ring\n");
                        return -EIO;
                }

                dev_rp = mhi_to_virtual(ev_ring, ptr);
                count++;
        }

        read_lock_bh(&mhi_cntrl->pm_lock);
        if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
                mhi_ring_er_db(mhi_event);
        read_unlock_bh(&mhi_cntrl->pm_lock);

        return count;
}

int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
                                struct mhi_event *mhi_event,
                                u32 event_quota)
{
        struct mhi_tre *dev_rp, *local_rp;
        struct mhi_ring *ev_ring = &mhi_event->ring;
        struct mhi_event_ctxt *er_ctxt =
                &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
        int count = 0;
        u32 chan;
        struct mhi_chan *mhi_chan;
        dma_addr_t ptr = er_ctxt->rp;

        if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
                return -EIO;

        if (!is_valid_ring_ptr(ev_ring, ptr)) {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Event ring rp points outside of the event ring\n");
                return -EIO;
        }

        dev_rp = mhi_to_virtual(ev_ring, ptr);
        local_rp = ev_ring->rp;

        while (dev_rp != local_rp && event_quota > 0) {
                enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);

                chan = MHI_TRE_GET_EV_CHID(local_rp);

                WARN_ON(chan >= mhi_cntrl->max_chan);

                /*
                 * Only process the event ring elements whose channel
                 * ID is within the maximum supported range.
                 */
                if (chan < mhi_cntrl->max_chan &&
                    mhi_cntrl->mhi_chan[chan].configured) {
                        mhi_chan = &mhi_cntrl->mhi_chan[chan];

                        if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
                                parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
                                event_quota--;
                        } else if (type == MHI_PKT_TYPE_RSC_TX_EVENT) {
                                parse_rsc_event(mhi_cntrl, local_rp, mhi_chan);
                                event_quota--;
                        }
                }

                mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
                local_rp = ev_ring->rp;

                ptr = er_ctxt->rp;
                if (!is_valid_ring_ptr(ev_ring, ptr)) {
                        dev_err(&mhi_cntrl->mhi_dev->dev,
                                "Event ring rp points outside of the event ring\n");
                        return -EIO;
                }

                dev_rp = mhi_to_virtual(ev_ring, ptr);
                count++;
        }
        read_lock_bh(&mhi_cntrl->pm_lock);
        if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
                mhi_ring_er_db(mhi_event);
        read_unlock_bh(&mhi_cntrl->pm_lock);

        return count;
}

void mhi_ev_task(unsigned long data)
{
        struct mhi_event *mhi_event = (struct mhi_event *)data;
        struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;

        /* process all pending events */
        spin_lock_bh(&mhi_event->lock);
        mhi_event->process_event(mhi_cntrl, mhi_event, U32_MAX);
        spin_unlock_bh(&mhi_event->lock);
}

void mhi_ctrl_ev_task(unsigned long data)
{
        struct mhi_event *mhi_event = (struct mhi_event *)data;
        struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        enum mhi_state state;
        enum mhi_pm_state pm_state = 0;
        int ret;

        /*
         * We can check PM state w/o a lock here because there is no way
         * PM state can change from reg access valid to no access while this
         * thread being executed.
         */
        if (!MHI_REG_ACCESS_VALID(mhi_cntrl->pm_state)) {
                /*
                 * We may have a pending event but not allowed to
                 * process it since we are probably in a suspended state,
                 * so trigger a resume.
                 */
                mhi_trigger_resume(mhi_cntrl);

                return;
        }

        /* Process ctrl events events */
        ret = mhi_event->process_event(mhi_cntrl, mhi_event, U32_MAX);

        /*
         * We received an IRQ but no events to process, maybe device went to
         * SYS_ERR state? Check the state to confirm.
         */
        if (!ret) {
                write_lock_irq(&mhi_cntrl->pm_lock);
                state = mhi_get_mhi_state(mhi_cntrl);
                if (state == MHI_STATE_SYS_ERR) {
                        dev_dbg(dev, "System error detected\n");
                        pm_state = mhi_tryset_pm_state(mhi_cntrl,
                                                       MHI_PM_SYS_ERR_DETECT);
                }
                write_unlock_irq(&mhi_cntrl->pm_lock);
                if (pm_state == MHI_PM_SYS_ERR_DETECT)
                        mhi_pm_sys_err_handler(mhi_cntrl);
        }
}

static bool mhi_is_ring_full(struct mhi_controller *mhi_cntrl,
                             struct mhi_ring *ring)
{
        void *tmp = ring->wp + ring->el_size;

        if (tmp >= (ring->base + ring->len))
                tmp = ring->base;

        return (tmp == ring->rp);
}

static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
                     enum dma_data_direction dir, enum mhi_flags mflags)
{
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ? mhi_dev->ul_chan :
                                                             mhi_dev->dl_chan;
        struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
        unsigned long flags;
        int ret;

        if (unlikely(MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)))
                return -EIO;

        read_lock_irqsave(&mhi_cntrl->pm_lock, flags);

        ret = mhi_is_ring_full(mhi_cntrl, tre_ring);
        if (unlikely(ret)) {
                ret = -EAGAIN;
                goto exit_unlock;
        }

        ret = mhi_gen_tre(mhi_cntrl, mhi_chan, buf_info, mflags);
        if (unlikely(ret))
                goto exit_unlock;

        /* Packet is queued, take a usage ref to exit M3 if necessary
         * for host->device buffer, balanced put is done on buffer completion
         * for device->host buffer, balanced put is after ringing the DB
         */
        mhi_cntrl->runtime_get(mhi_cntrl);

        /* Assert dev_wake (to exit/prevent M1/M2)*/
        mhi_cntrl->wake_toggle(mhi_cntrl);

        if (mhi_chan->dir == DMA_TO_DEVICE)
                atomic_inc(&mhi_cntrl->pending_pkts);

        if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
                mhi_ring_chan_db(mhi_cntrl, mhi_chan);

        if (dir == DMA_FROM_DEVICE)
                mhi_cntrl->runtime_put(mhi_cntrl);

exit_unlock:
        read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);

        return ret;
}

int mhi_queue_skb(struct mhi_device *mhi_dev, enum dma_data_direction dir,
                  struct sk_buff *skb, size_t len, enum mhi_flags mflags)
{
        struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ? mhi_dev->ul_chan :
                                                             mhi_dev->dl_chan;
        struct mhi_buf_info buf_info = { };

        buf_info.v_addr = skb->data;
        buf_info.cb_buf = skb;
        buf_info.len = len;

        if (unlikely(mhi_chan->pre_alloc))
                return -EINVAL;

        return mhi_queue(mhi_dev, &buf_info, dir, mflags);
}
EXPORT_SYMBOL_GPL(mhi_queue_skb);

int mhi_queue_dma(struct mhi_device *mhi_dev, enum dma_data_direction dir,
                  struct mhi_buf *mhi_buf, size_t len, enum mhi_flags mflags)
{
        struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ? mhi_dev->ul_chan :
                                                             mhi_dev->dl_chan;
        struct mhi_buf_info buf_info = { };

        buf_info.p_addr = mhi_buf->dma_addr;
        buf_info.cb_buf = mhi_buf;
        buf_info.pre_mapped = true;
        buf_info.len = len;

        if (unlikely(mhi_chan->pre_alloc))
                return -EINVAL;

        return mhi_queue(mhi_dev, &buf_info, dir, mflags);
}
EXPORT_SYMBOL_GPL(mhi_queue_dma);

int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
                        struct mhi_buf_info *info, enum mhi_flags flags)
{
        struct mhi_ring *buf_ring, *tre_ring;
        struct mhi_tre *mhi_tre;
        struct mhi_buf_info *buf_info;
        int eot, eob, chain, bei;
        int ret;

        buf_ring = &mhi_chan->buf_ring;
        tre_ring = &mhi_chan->tre_ring;

        buf_info = buf_ring->wp;
        WARN_ON(buf_info->used);
        buf_info->pre_mapped = info->pre_mapped;
        if (info->pre_mapped)
                buf_info->p_addr = info->p_addr;
        else
                buf_info->v_addr = info->v_addr;
        buf_info->cb_buf = info->cb_buf;
        buf_info->wp = tre_ring->wp;
        buf_info->dir = mhi_chan->dir;
        buf_info->len = info->len;

        if (!info->pre_mapped) {
                ret = mhi_cntrl->map_single(mhi_cntrl, buf_info);
                if (ret)
                        return ret;
        }

        eob = !!(flags & MHI_EOB);
        eot = !!(flags & MHI_EOT);
        chain = !!(flags & MHI_CHAIN);
        bei = !!(mhi_chan->intmod);

        mhi_tre = tre_ring->wp;
        mhi_tre->ptr = MHI_TRE_DATA_PTR(buf_info->p_addr);
        mhi_tre->dword[0] = MHI_TRE_DATA_DWORD0(info->len);
        mhi_tre->dword[1] = MHI_TRE_DATA_DWORD1(bei, eot, eob, chain);

        /* increment WP */
        mhi_add_ring_element(mhi_cntrl, tre_ring);
        mhi_add_ring_element(mhi_cntrl, buf_ring);

        return 0;
}

int mhi_queue_buf(struct mhi_device *mhi_dev, enum dma_data_direction dir,
                  void *buf, size_t len, enum mhi_flags mflags)
{
        struct mhi_buf_info buf_info = { };

        buf_info.v_addr = buf;
        buf_info.cb_buf = buf;
        buf_info.len = len;

        return mhi_queue(mhi_dev, &buf_info, dir, mflags);
}
EXPORT_SYMBOL_GPL(mhi_queue_buf);

bool mhi_queue_is_full(struct mhi_device *mhi_dev, enum dma_data_direction dir)
{
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ?
                                        mhi_dev->ul_chan : mhi_dev->dl_chan;
        struct mhi_ring *tre_ring = &mhi_chan->tre_ring;

        return mhi_is_ring_full(mhi_cntrl, tre_ring);
}
EXPORT_SYMBOL_GPL(mhi_queue_is_full);

int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
                 struct mhi_chan *mhi_chan,
                 enum mhi_cmd_type cmd)
{
        struct mhi_tre *cmd_tre = NULL;
        struct mhi_cmd *mhi_cmd = &mhi_cntrl->mhi_cmd[PRIMARY_CMD_RING];
        struct mhi_ring *ring = &mhi_cmd->ring;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        int chan = 0;

        if (mhi_chan)
                chan = mhi_chan->chan;

        spin_lock_bh(&mhi_cmd->lock);
        if (!get_nr_avail_ring_elements(mhi_cntrl, ring)) {
                spin_unlock_bh(&mhi_cmd->lock);
                return -ENOMEM;
        }

        /* prepare the cmd tre */
        cmd_tre = ring->wp;
        switch (cmd) {
        case MHI_CMD_RESET_CHAN:
                cmd_tre->ptr = MHI_TRE_CMD_RESET_PTR;
                cmd_tre->dword[0] = MHI_TRE_CMD_RESET_DWORD0;
                cmd_tre->dword[1] = MHI_TRE_CMD_RESET_DWORD1(chan);
                break;
        case MHI_CMD_STOP_CHAN:
                cmd_tre->ptr = MHI_TRE_CMD_STOP_PTR;
                cmd_tre->dword[0] = MHI_TRE_CMD_STOP_DWORD0;
                cmd_tre->dword[1] = MHI_TRE_CMD_STOP_DWORD1(chan);
                break;
        case MHI_CMD_START_CHAN:
                cmd_tre->ptr = MHI_TRE_CMD_START_PTR;
                cmd_tre->dword[0] = MHI_TRE_CMD_START_DWORD0;
                cmd_tre->dword[1] = MHI_TRE_CMD_START_DWORD1(chan);
                break;
        default:
                dev_err(dev, "Command not supported\n");
                break;
        }

        /* queue to hardware */
        mhi_add_ring_element(mhi_cntrl, ring);
        read_lock_bh(&mhi_cntrl->pm_lock);
        if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
                mhi_ring_cmd_db(mhi_cntrl, mhi_cmd);
        read_unlock_bh(&mhi_cntrl->pm_lock);
        spin_unlock_bh(&mhi_cmd->lock);

        return 0;
}

static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
                                    struct mhi_chan *mhi_chan,
                                    enum mhi_ch_state_type to_state)
{
        struct device *dev = &mhi_chan->mhi_dev->dev;
        enum mhi_cmd_type cmd = MHI_CMD_NOP;
        int ret;

        dev_dbg(dev, "%d: Updating channel state to: %s\n", mhi_chan->chan,
                TO_CH_STATE_TYPE_STR(to_state));

        switch (to_state) {
        case MHI_CH_STATE_TYPE_RESET:
                write_lock_irq(&mhi_chan->lock);
                if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
                    mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
                    mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
                        write_unlock_irq(&mhi_chan->lock);
                        return -EINVAL;
                }
                mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
                write_unlock_irq(&mhi_chan->lock);

                cmd = MHI_CMD_RESET_CHAN;
                break;
        case MHI_CH_STATE_TYPE_STOP:
                if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
                        return -EINVAL;

                cmd = MHI_CMD_STOP_CHAN;
                break;
        case MHI_CH_STATE_TYPE_START:
                if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
                    mhi_chan->ch_state != MHI_CH_STATE_DISABLED)
                        return -EINVAL;

                cmd = MHI_CMD_START_CHAN;
                break;
        default:
                dev_err(dev, "%d: Channel state update to %s not allowed\n",
                        mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
                return -EINVAL;
        }

        /* bring host and device out of suspended states */
        ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
        if (ret)
                return ret;
        mhi_cntrl->runtime_get(mhi_cntrl);

        reinit_completion(&mhi_chan->completion);
        ret = mhi_send_cmd(mhi_cntrl, mhi_chan, cmd);
        if (ret) {
                dev_err(dev, "%d: Failed to send %s channel command\n",
                        mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
                goto exit_channel_update;
        }

        ret = wait_for_completion_timeout(&mhi_chan->completion,
                                       msecs_to_jiffies(mhi_cntrl->timeout_ms));
        if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS) {
                dev_err(dev,
                        "%d: Failed to receive %s channel command completion\n",
                        mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
                ret = -EIO;
                goto exit_channel_update;
        }

        ret = 0;

        if (to_state != MHI_CH_STATE_TYPE_RESET) {
                write_lock_irq(&mhi_chan->lock);
                mhi_chan->ch_state = (to_state == MHI_CH_STATE_TYPE_START) ?
                                      MHI_CH_STATE_ENABLED : MHI_CH_STATE_STOP;
                write_unlock_irq(&mhi_chan->lock);
        }

        dev_dbg(dev, "%d: Channel state change to %s successful\n",
                mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));

exit_channel_update:
        mhi_cntrl->runtime_put(mhi_cntrl);
        mhi_device_put(mhi_cntrl->mhi_dev);

        return ret;
}

static void mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
                                  struct mhi_chan *mhi_chan)
{
        int ret;
        struct device *dev = &mhi_chan->mhi_dev->dev;

        mutex_lock(&mhi_chan->mutex);

        if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
                dev_dbg(dev, "Current EE: %s Required EE Mask: 0x%x\n",
                        TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
                goto exit_unprepare_channel;
        }

        /* no more processing events for this channel */
        ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
                                       MHI_CH_STATE_TYPE_RESET);
        if (ret)
                dev_err(dev, "%d: Failed to reset channel, still resetting\n",
                        mhi_chan->chan);

exit_unprepare_channel:
        write_lock_irq(&mhi_chan->lock);
        mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
        write_unlock_irq(&mhi_chan->lock);

        if (!mhi_chan->offload_ch) {
                mhi_reset_chan(mhi_cntrl, mhi_chan);
                mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
        }
        dev_dbg(dev, "%d: successfully reset\n", mhi_chan->chan);

        mutex_unlock(&mhi_chan->mutex);
}

int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
                        struct mhi_chan *mhi_chan)
{
        int ret = 0;
        struct device *dev = &mhi_chan->mhi_dev->dev;

        if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
                dev_err(dev, "Current EE: %s Required EE Mask: 0x%x\n",
                        TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
                return -ENOTCONN;
        }

        mutex_lock(&mhi_chan->mutex);

        /* Check of client manages channel context for offload channels */
        if (!mhi_chan->offload_ch) {
                ret = mhi_init_chan_ctxt(mhi_cntrl, mhi_chan);
                if (ret)
                        goto error_init_chan;
        }

        ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
                                       MHI_CH_STATE_TYPE_START);
        if (ret)
                goto error_pm_state;

        /* Pre-allocate buffer for xfer ring */
        if (mhi_chan->pre_alloc) {
                int nr_el = get_nr_avail_ring_elements(mhi_cntrl,
                                                       &mhi_chan->tre_ring);
                size_t len = mhi_cntrl->buffer_len;

                while (nr_el--) {
                        void *buf;
                        struct mhi_buf_info info = { };
                        buf = kmalloc(len, GFP_KERNEL);
                        if (!buf) {
                                ret = -ENOMEM;
                                goto error_pre_alloc;
                        }

                        /* Prepare transfer descriptors */
                        info.v_addr = buf;
                        info.cb_buf = buf;
                        info.len = len;
                        ret = mhi_gen_tre(mhi_cntrl, mhi_chan, &info, MHI_EOT);
                        if (ret) {
                                kfree(buf);
                                goto error_pre_alloc;
                        }
                }

                read_lock_bh(&mhi_cntrl->pm_lock);
                if (MHI_DB_ACCESS_VALID(mhi_cntrl)) {
                        read_lock_irq(&mhi_chan->lock);
                        mhi_ring_chan_db(mhi_cntrl, mhi_chan);
                        read_unlock_irq(&mhi_chan->lock);
                }
                read_unlock_bh(&mhi_cntrl->pm_lock);
        }

        mutex_unlock(&mhi_chan->mutex);

        return 0;

error_pm_state:
        if (!mhi_chan->offload_ch)
                mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);

error_init_chan:
        mutex_unlock(&mhi_chan->mutex);

        return ret;

error_pre_alloc:
        mutex_unlock(&mhi_chan->mutex);
        mhi_unprepare_channel(mhi_cntrl, mhi_chan);

        return ret;
}

static void mhi_mark_stale_events(struct mhi_controller *mhi_cntrl,
                                  struct mhi_event *mhi_event,
                                  struct mhi_event_ctxt *er_ctxt,
                                  int chan)

{
        struct mhi_tre *dev_rp, *local_rp;
        struct mhi_ring *ev_ring;
        struct device *dev = &mhi_cntrl->mhi_dev->dev;
        unsigned long flags;
        dma_addr_t ptr;

        dev_dbg(dev, "Marking all events for chan: %d as stale\n", chan);

        ev_ring = &mhi_event->ring;

        /* mark all stale events related to channel as STALE event */
        spin_lock_irqsave(&mhi_event->lock, flags);

        ptr = er_ctxt->rp;
        if (!is_valid_ring_ptr(ev_ring, ptr)) {
                dev_err(&mhi_cntrl->mhi_dev->dev,
                        "Event ring rp points outside of the event ring\n");
                dev_rp = ev_ring->rp;
        } else {
                dev_rp = mhi_to_virtual(ev_ring, ptr);
        }

        local_rp = ev_ring->rp;
        while (dev_rp != local_rp) {
                if (MHI_TRE_GET_EV_TYPE(local_rp) == MHI_PKT_TYPE_TX_EVENT &&
                    chan == MHI_TRE_GET_EV_CHID(local_rp))
                        local_rp->dword[1] = MHI_TRE_EV_DWORD1(chan,
                                        MHI_PKT_TYPE_STALE_EVENT);
                local_rp++;
                if (local_rp == (ev_ring->base + ev_ring->len))
                        local_rp = ev_ring->base;
        }

        dev_dbg(dev, "Finished marking events as stale events\n");
        spin_unlock_irqrestore(&mhi_event->lock, flags);
}

static void mhi_reset_data_chan(struct mhi_controller *mhi_cntrl,
                                struct mhi_chan *mhi_chan)
{
        struct mhi_ring *buf_ring, *tre_ring;
        struct mhi_result result;

        /* Reset any pending buffers */
        buf_ring = &mhi_chan->buf_ring;
        tre_ring = &mhi_chan->tre_ring;
        result.transaction_status = -ENOTCONN;
        result.bytes_xferd = 0;
        while (tre_ring->rp != tre_ring->wp) {
                struct mhi_buf_info *buf_info = buf_ring->rp;

                if (mhi_chan->dir == DMA_TO_DEVICE) {
                        atomic_dec(&mhi_cntrl->pending_pkts);
                        /* Release the reference got from mhi_queue() */
                        mhi_cntrl->runtime_put(mhi_cntrl);
                }

                if (!buf_info->pre_mapped)
                        mhi_cntrl->unmap_single(mhi_cntrl, buf_info);

                mhi_del_ring_element(mhi_cntrl, buf_ring);
                mhi_del_ring_element(mhi_cntrl, tre_ring);

                if (mhi_chan->pre_alloc) {
                        kfree(buf_info->cb_buf);
                } else {
                        result.buf_addr = buf_info->cb_buf;
                        mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
                }
        }
}

void mhi_reset_chan(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan)
{
        struct mhi_event *mhi_event;
        struct mhi_event_ctxt *er_ctxt;
        int chan = mhi_chan->chan;

        /* Nothing to reset, client doesn't queue buffers */
        if (mhi_chan->offload_ch)
                return;

        read_lock_bh(&mhi_cntrl->pm_lock);
        mhi_event = &mhi_cntrl->mhi_event[mhi_chan->er_index];
        er_ctxt = &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_chan->er_index];

        mhi_mark_stale_events(mhi_cntrl, mhi_event, er_ctxt, chan);

        mhi_reset_data_chan(mhi_cntrl, mhi_chan);

        read_unlock_bh(&mhi_cntrl->pm_lock);
}

/* Move channel to start state */
int mhi_prepare_for_transfer(struct mhi_device *mhi_dev)
{
        int ret, dir;
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan;

        for (dir = 0; dir < 2; dir++) {
                mhi_chan = dir ? mhi_dev->dl_chan : mhi_dev->ul_chan;
                if (!mhi_chan)
                        continue;

                ret = mhi_prepare_channel(mhi_cntrl, mhi_chan);
                if (ret)
                        goto error_open_chan;
        }

        return 0;

error_open_chan:
        for (--dir; dir >= 0; dir--) {
                mhi_chan = dir ? mhi_dev->dl_chan : mhi_dev->ul_chan;
                if (!mhi_chan)
                        continue;

                mhi_unprepare_channel(mhi_cntrl, mhi_chan);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(mhi_prepare_for_transfer);

void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
{
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan;
        int dir;

        for (dir = 0; dir < 2; dir++) {
                mhi_chan = dir ? mhi_dev->ul_chan : mhi_dev->dl_chan;
                if (!mhi_chan)
                        continue;

                mhi_unprepare_channel(mhi_cntrl, mhi_chan);
        }
}
EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);

int mhi_poll(struct mhi_device *mhi_dev, u32 budget)
{
        struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
        struct mhi_chan *mhi_chan = mhi_dev->dl_chan;
        struct mhi_event *mhi_event = &mhi_cntrl->mhi_event[mhi_chan->er_index];
        int ret;

        spin_lock_bh(&mhi_event->lock);
        ret = mhi_event->process_event(mhi_cntrl, mhi_event, budget);
        spin_unlock_bh(&mhi_event->lock);

        return ret;
}
EXPORT_SYMBOL_GPL(mhi_poll);