// SPDX-License-Identifier: GPL-2.0
/*
 *
 * MMC software queue support based on command queue interfaces
 *
 * Copyright (C) 2019 Linaro, Inc.
 * Author: Baolin Wang <baolin.wang@linaro.org>
 */

#include <linux/mmc/card.h>
#include <linux/mmc/host.h>
#include <linux/module.h>

#include "mmc_hsq.h"

#define HSQ_NUM_SLOTS   64
#define HSQ_INVALID_TAG HSQ_NUM_SLOTS

static void mmc_hsq_retry_handler(struct work_struct *work)
{
        struct mmc_hsq *hsq = container_of(work, struct mmc_hsq, retry_work);
        struct mmc_host *mmc = hsq->mmc;

        mmc->ops->request(mmc, hsq->mrq);
}

static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
{
        struct mmc_host *mmc = hsq->mmc;
        struct hsq_slot *slot;
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&hsq->lock, flags);

        /* Make sure we are not already running a request now */
        if (hsq->mrq) {
                spin_unlock_irqrestore(&hsq->lock, flags);
                return;
        }

        /* Make sure there are remain requests need to pump */
        if (!hsq->qcnt || !hsq->enabled) {
                spin_unlock_irqrestore(&hsq->lock, flags);
                return;
        }

        slot = &hsq->slot[hsq->next_tag];
        hsq->mrq = slot->mrq;
        hsq->qcnt--;

        spin_unlock_irqrestore(&hsq->lock, flags);

        if (mmc->ops->request_atomic)
                ret = mmc->ops->request_atomic(mmc, hsq->mrq);
        else
                mmc->ops->request(mmc, hsq->mrq);

        /*
         * If returning BUSY from request_atomic(), which means the card
         * may be busy now, and we should change to non-atomic context to
         * try again for this unusual case, to avoid time-consuming operations
         * in the atomic context.
         *
         * Note: we just give a warning for other error cases, since the host
         * driver will handle them.
         */
        if (ret == -EBUSY)
                schedule_work(&hsq->retry_work);
        else
                WARN_ON_ONCE(ret);
}

static void mmc_hsq_update_next_tag(struct mmc_hsq *hsq, int remains)
{
        struct hsq_slot *slot;
        int tag;

        /*
         * If there are no remain requests in software queue, then set a invalid
         * tag.
         */
        if (!remains) {
                hsq->next_tag = HSQ_INVALID_TAG;
                return;
        }

        /*
         * Increasing the next tag and check if the corresponding request is
         * available, if yes, then we found a candidate request.
         */
        if (++hsq->next_tag != HSQ_INVALID_TAG) {
                slot = &hsq->slot[hsq->next_tag];
                if (slot->mrq)
                        return;
        }

        /* Othersie we should iterate all slots to find a available tag. */
        for (tag = 0; tag < HSQ_NUM_SLOTS; tag++) {
                slot = &hsq->slot[tag];
                if (slot->mrq)
                        break;
        }

        if (tag == HSQ_NUM_SLOTS)
                tag = HSQ_INVALID_TAG;

        hsq->next_tag = tag;
}

static void mmc_hsq_post_request(struct mmc_hsq *hsq)
{
        unsigned long flags;
        int remains;

        spin_lock_irqsave(&hsq->lock, flags);

        remains = hsq->qcnt;
        hsq->mrq = NULL;

        /* Update the next available tag to be queued. */
        mmc_hsq_update_next_tag(hsq, remains);

        if (hsq->waiting_for_idle && !remains) {
                hsq->waiting_for_idle = false;
                wake_up(&hsq->wait_queue);
        }

        /* Do not pump new request in recovery mode. */
        if (hsq->recovery_halt) {
                spin_unlock_irqrestore(&hsq->lock, flags);
                return;
        }

        spin_unlock_irqrestore(&hsq->lock, flags);

         /*
          * Try to pump new request to host controller as fast as possible,
          * after completing previous request.
          */
        if (remains > 0)
                mmc_hsq_pump_requests(hsq);
}

/**
 * mmc_hsq_finalize_request - finalize one request if the request is done
 * @mmc: the host controller
 * @mrq: the request need to be finalized
 *
 * Return true if we finalized the corresponding request in software queue,
 * otherwise return false.
 */
bool mmc_hsq_finalize_request(struct mmc_host *mmc, struct mmc_request *mrq)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        unsigned long flags;

        spin_lock_irqsave(&hsq->lock, flags);

        if (!hsq->enabled || !hsq->mrq || hsq->mrq != mrq) {
                spin_unlock_irqrestore(&hsq->lock, flags);
                return false;
        }

        /*
         * Clear current completed slot request to make a room for new request.
         */
        hsq->slot[hsq->next_tag].mrq = NULL;

        spin_unlock_irqrestore(&hsq->lock, flags);

        mmc_cqe_request_done(mmc, hsq->mrq);

        mmc_hsq_post_request(hsq);

        return true;
}
EXPORT_SYMBOL_GPL(mmc_hsq_finalize_request);

static void mmc_hsq_recovery_start(struct mmc_host *mmc)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        unsigned long flags;

        spin_lock_irqsave(&hsq->lock, flags);

        hsq->recovery_halt = true;

        spin_unlock_irqrestore(&hsq->lock, flags);
}

static void mmc_hsq_recovery_finish(struct mmc_host *mmc)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        int remains;

        spin_lock_irq(&hsq->lock);

        hsq->recovery_halt = false;
        remains = hsq->qcnt;

        spin_unlock_irq(&hsq->lock);

        /*
         * Try to pump new request if there are request pending in software
         * queue after finishing recovery.
         */
        if (remains > 0)
                mmc_hsq_pump_requests(hsq);
}

static int mmc_hsq_request(struct mmc_host *mmc, struct mmc_request *mrq)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        int tag = mrq->tag;

        spin_lock_irq(&hsq->lock);

        if (!hsq->enabled) {
                spin_unlock_irq(&hsq->lock);
                return -ESHUTDOWN;
        }

        /* Do not queue any new requests in recovery mode. */
        if (hsq->recovery_halt) {
                spin_unlock_irq(&hsq->lock);
                return -EBUSY;
        }

        hsq->slot[tag].mrq = mrq;

        /*
         * Set the next tag as current request tag if no available
         * next tag.
         */
        if (hsq->next_tag == HSQ_INVALID_TAG)
                hsq->next_tag = tag;

        hsq->qcnt++;

        spin_unlock_irq(&hsq->lock);

        mmc_hsq_pump_requests(hsq);

        return 0;
}

static void mmc_hsq_post_req(struct mmc_host *mmc, struct mmc_request *mrq)
{
        if (mmc->ops->post_req)
                mmc->ops->post_req(mmc, mrq, 0);
}

static bool mmc_hsq_queue_is_idle(struct mmc_hsq *hsq, int *ret)
{
        bool is_idle;

        spin_lock_irq(&hsq->lock);

        is_idle = (!hsq->mrq && !hsq->qcnt) ||
                hsq->recovery_halt;

        *ret = hsq->recovery_halt ? -EBUSY : 0;
        hsq->waiting_for_idle = !is_idle;

        spin_unlock_irq(&hsq->lock);

        return is_idle;
}

static int mmc_hsq_wait_for_idle(struct mmc_host *mmc)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        int ret;

        wait_event(hsq->wait_queue,
                   mmc_hsq_queue_is_idle(hsq, &ret));

        return ret;
}

static void mmc_hsq_disable(struct mmc_host *mmc)
{
        struct mmc_hsq *hsq = mmc->cqe_private;
        u32 timeout = 500;
        int ret;

        spin_lock_irq(&hsq->lock);

        if (!hsq->enabled) {
                spin_unlock_irq(&hsq->lock);
                return;
        }

        spin_unlock_irq(&hsq->lock);

        ret = wait_event_timeout(hsq->wait_queue,
                                 mmc_hsq_queue_is_idle(hsq, &ret),
                                 msecs_to_jiffies(timeout));
        if (ret == 0) {
                pr_warn("could not stop mmc software queue\n");
                return;
        }

        spin_lock_irq(&hsq->lock);

        hsq->enabled = false;

        spin_unlock_irq(&hsq->lock);
}

static int mmc_hsq_enable(struct mmc_host *mmc, struct mmc_card *card)
{
        struct mmc_hsq *hsq = mmc->cqe_private;

        spin_lock_irq(&hsq->lock);

        if (hsq->enabled) {
                spin_unlock_irq(&hsq->lock);
                return -EBUSY;
        }

        hsq->enabled = true;

        spin_unlock_irq(&hsq->lock);

        return 0;
}

static const struct mmc_cqe_ops mmc_hsq_ops = {
        .cqe_enable = mmc_hsq_enable,
        .cqe_disable = mmc_hsq_disable,
        .cqe_request = mmc_hsq_request,
        .cqe_post_req = mmc_hsq_post_req,
        .cqe_wait_for_idle = mmc_hsq_wait_for_idle,
        .cqe_recovery_start = mmc_hsq_recovery_start,
        .cqe_recovery_finish = mmc_hsq_recovery_finish,
};

int mmc_hsq_init(struct mmc_hsq *hsq, struct mmc_host *mmc)
{
        hsq->num_slots = HSQ_NUM_SLOTS;
        hsq->next_tag = HSQ_INVALID_TAG;

        hsq->slot = devm_kcalloc(mmc_dev(mmc), hsq->num_slots,
                                 sizeof(struct hsq_slot), GFP_KERNEL);
        if (!hsq->slot)
                return -ENOMEM;

        hsq->mmc = mmc;
        hsq->mmc->cqe_private = hsq;
        mmc->cqe_ops = &mmc_hsq_ops;

        INIT_WORK(&hsq->retry_work, mmc_hsq_retry_handler);
        spin_lock_init(&hsq->lock);
        init_waitqueue_head(&hsq->wait_queue);

        return 0;
}
EXPORT_SYMBOL_GPL(mmc_hsq_init);

void mmc_hsq_suspend(struct mmc_host *mmc)
{
        mmc_hsq_disable(mmc);
}
EXPORT_SYMBOL_GPL(mmc_hsq_suspend);

int mmc_hsq_resume(struct mmc_host *mmc)
{
        return mmc_hsq_enable(mmc, NULL);
}
EXPORT_SYMBOL_GPL(mmc_hsq_resume);

MODULE_DESCRIPTION("MMC Host Software Queue support");
MODULE_LICENSE("GPL v2");