// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2017-2018 MediaTek Inc.

/*
 * Driver for MediaTek High-Speed DMA Controller
 *
 * Author: Sean Wang <sean.wang@mediatek.com>
 *
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/iopoll.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/refcount.h>
#include <linux/slab.h>

#include "../virt-dma.h"

#define MTK_HSDMA_USEC_POLL             20
#define MTK_HSDMA_TIMEOUT_POLL          200000
#define MTK_HSDMA_DMA_BUSWIDTHS         BIT(DMA_SLAVE_BUSWIDTH_4_BYTES)

/* The default number of virtual channel */
#define MTK_HSDMA_NR_VCHANS             3

/* Only one physical channel supported */
#define MTK_HSDMA_NR_MAX_PCHANS         1

/* Macro for physical descriptor (PD) manipulation */
/* The number of PD which must be 2 of power */
#define MTK_DMA_SIZE                    64
#define MTK_HSDMA_NEXT_DESP_IDX(x, y)   (((x) + 1) & ((y) - 1))
#define MTK_HSDMA_LAST_DESP_IDX(x, y)   (((x) - 1) & ((y) - 1))
#define MTK_HSDMA_MAX_LEN               0x3f80
#define MTK_HSDMA_ALIGN_SIZE            4
#define MTK_HSDMA_PLEN_MASK             0x3fff
#define MTK_HSDMA_DESC_PLEN(x)          (((x) & MTK_HSDMA_PLEN_MASK) << 16)
#define MTK_HSDMA_DESC_PLEN_GET(x)      (((x) >> 16) & MTK_HSDMA_PLEN_MASK)

/* Registers for underlying ring manipulation */
#define MTK_HSDMA_TX_BASE               0x0
#define MTK_HSDMA_TX_CNT                0x4
#define MTK_HSDMA_TX_CPU                0x8
#define MTK_HSDMA_TX_DMA                0xc
#define MTK_HSDMA_RX_BASE               0x100
#define MTK_HSDMA_RX_CNT                0x104
#define MTK_HSDMA_RX_CPU                0x108
#define MTK_HSDMA_RX_DMA                0x10c

/* Registers for global setup */
#define MTK_HSDMA_GLO                   0x204
#define MTK_HSDMA_GLO_MULTI_DMA         BIT(10)
#define MTK_HSDMA_TX_WB_DDONE           BIT(6)
#define MTK_HSDMA_BURST_64BYTES         (0x2 << 4)
#define MTK_HSDMA_GLO_RX_BUSY           BIT(3)
#define MTK_HSDMA_GLO_RX_DMA            BIT(2)
#define MTK_HSDMA_GLO_TX_BUSY           BIT(1)
#define MTK_HSDMA_GLO_TX_DMA            BIT(0)
#define MTK_HSDMA_GLO_DMA               (MTK_HSDMA_GLO_TX_DMA | \
                                         MTK_HSDMA_GLO_RX_DMA)
#define MTK_HSDMA_GLO_BUSY              (MTK_HSDMA_GLO_RX_BUSY | \
                                         MTK_HSDMA_GLO_TX_BUSY)
#define MTK_HSDMA_GLO_DEFAULT           (MTK_HSDMA_GLO_TX_DMA | \
                                         MTK_HSDMA_GLO_RX_DMA | \
                                         MTK_HSDMA_TX_WB_DDONE | \
                                         MTK_HSDMA_BURST_64BYTES | \
                                         MTK_HSDMA_GLO_MULTI_DMA)

/* Registers for reset */
#define MTK_HSDMA_RESET                 0x208
#define MTK_HSDMA_RST_TX                BIT(0)
#define MTK_HSDMA_RST_RX                BIT(16)

/* Registers for interrupt control */
#define MTK_HSDMA_DLYINT                0x20c
#define MTK_HSDMA_RXDLY_INT_EN          BIT(15)

/* Interrupt fires when the pending number's more than the specified */
#define MTK_HSDMA_RXMAX_PINT(x)         (((x) & 0x7f) << 8)

/* Interrupt fires when the pending time's more than the specified in 20 us */
#define MTK_HSDMA_RXMAX_PTIME(x)        ((x) & 0x7f)
#define MTK_HSDMA_DLYINT_DEFAULT        (MTK_HSDMA_RXDLY_INT_EN | \
                                         MTK_HSDMA_RXMAX_PINT(20) | \
                                         MTK_HSDMA_RXMAX_PTIME(20))
#define MTK_HSDMA_INT_STATUS            0x220
#define MTK_HSDMA_INT_ENABLE            0x228
#define MTK_HSDMA_INT_RXDONE            BIT(16)

enum mtk_hsdma_vdesc_flag {
        MTK_HSDMA_VDESC_FINISHED        = 0x01,
};

#define IS_MTK_HSDMA_VDESC_FINISHED(x) ((x) == MTK_HSDMA_VDESC_FINISHED)

/**
 * struct mtk_hsdma_pdesc - This is the struct holding info describing physical
 *                          descriptor (PD) and its placement must be kept at
 *                          4-bytes alignment in little endian order.
 * @desc[1-4]:              The control pad used to indicate hardware how to
 *                          deal with the descriptor such as source and
 *                          destination address and data length. The maximum
 *                          data length each pdesc can handle is 0x3f80 bytes
 */
struct mtk_hsdma_pdesc {
        __le32 desc1;
        __le32 desc2;
        __le32 desc3;
        __le32 desc4;
} __packed __aligned(4);

/**
 * struct mtk_hsdma_vdesc - This is the struct holding info describing virtual
 *                          descriptor (VD)
 * @vd:                     An instance for struct virt_dma_desc
 * @len:                    The total data size device wants to move
 * @residue:                The remaining data size device will move
 * @dest:                   The destination address device wants to move to
 * @src:                    The source address device wants to move from
 */
struct mtk_hsdma_vdesc {
        struct virt_dma_desc vd;
        size_t len;
        size_t residue;
        dma_addr_t dest;
        dma_addr_t src;
};

/**
 * struct mtk_hsdma_cb - This is the struct holding extra info required for RX
 *                       ring to know what relevant VD the the PD is being
 *                       mapped to.
 * @vd:                  Pointer to the relevant VD.
 * @flag:                Flag indicating what action should be taken when VD
 *                       is completed.
 */
struct mtk_hsdma_cb {
        struct virt_dma_desc *vd;
        enum mtk_hsdma_vdesc_flag flag;
};

/**
 * struct mtk_hsdma_ring - This struct holds info describing underlying ring
 *                         space
 * @txd:                   The descriptor TX ring which describes DMA source
 *                         information
 * @rxd:                   The descriptor RX ring which describes DMA
 *                         destination information
 * @cb:                    The extra information pointed at by RX ring
 * @tphys:                 The physical addr of TX ring
 * @rphys:                 The physical addr of RX ring
 * @cur_tptr:              Pointer to the next free descriptor used by the host
 * @cur_rptr:              Pointer to the last done descriptor by the device
 */
struct mtk_hsdma_ring {
        struct mtk_hsdma_pdesc *txd;
        struct mtk_hsdma_pdesc *rxd;
        struct mtk_hsdma_cb *cb;
        dma_addr_t tphys;
        dma_addr_t rphys;
        u16 cur_tptr;
        u16 cur_rptr;
};

/**
 * struct mtk_hsdma_pchan - This is the struct holding info describing physical
 *                         channel (PC)
 * @ring:                  An instance for the underlying ring
 * @sz_ring:               Total size allocated for the ring
 * @nr_free:               Total number of free rooms in the ring. It would
 *                         be accessed and updated frequently between IRQ
 *                         context and user context to reflect whether ring
 *                         can accept requests from VD.
 */
struct mtk_hsdma_pchan {
        struct mtk_hsdma_ring ring;
        size_t sz_ring;
        atomic_t nr_free;
};

/**
 * struct mtk_hsdma_vchan - This is the struct holding info describing virtual
 *                         channel (VC)
 * @vc:                    An instance for struct virt_dma_chan
 * @issue_completion:      The wait for all issued descriptors completited
 * @issue_synchronize:     Bool indicating channel synchronization starts
 * @desc_hw_processing:    List those descriptors the hardware is processing,
 *                         which is protected by vc.lock
 */
struct mtk_hsdma_vchan {
        struct virt_dma_chan vc;
        struct completion issue_completion;
        bool issue_synchronize;
        struct list_head desc_hw_processing;
};

/**
 * struct mtk_hsdma_soc - This is the struct holding differences among SoCs
 * @ddone:                Bit mask for DDONE
 * @ls0:                  Bit mask for LS0
 */
struct mtk_hsdma_soc {
        __le32 ddone;
        __le32 ls0;
};

/**
 * struct mtk_hsdma_device - This is the struct holding info describing HSDMA
 *                           device
 * @ddev:                    An instance for struct dma_device
 * @base:                    The mapped register I/O base
 * @clk:                     The clock that device internal is using
 * @irq:                     The IRQ that device are using
 * @dma_requests:            The number of VCs the device supports to
 * @vc:                      The pointer to all available VCs
 * @pc:                      The pointer to the underlying PC
 * @pc_refcnt:               Track how many VCs are using the PC
 * @lock:                    Lock protect agaisting multiple VCs access PC
 * @soc:                     The pointer to area holding differences among
 *                           vaious platform
 */
struct mtk_hsdma_device {
        struct dma_device ddev;
        void __iomem *base;
        struct clk *clk;
        u32 irq;

        u32 dma_requests;
        struct mtk_hsdma_vchan *vc;
        struct mtk_hsdma_pchan *pc;
        refcount_t pc_refcnt;

        /* Lock used to protect against multiple VCs access PC */
        spinlock_t lock;

        const struct mtk_hsdma_soc *soc;
};

static struct mtk_hsdma_device *to_hsdma_dev(struct dma_chan *chan)
{
        return container_of(chan->device, struct mtk_hsdma_device, ddev);
}

static inline struct mtk_hsdma_vchan *to_hsdma_vchan(struct dma_chan *chan)
{
        return container_of(chan, struct mtk_hsdma_vchan, vc.chan);
}

static struct mtk_hsdma_vdesc *to_hsdma_vdesc(struct virt_dma_desc *vd)
{
        return container_of(vd, struct mtk_hsdma_vdesc, vd);
}

static struct device *hsdma2dev(struct mtk_hsdma_device *hsdma)
{
        return hsdma->ddev.dev;
}

static u32 mtk_dma_read(struct mtk_hsdma_device *hsdma, u32 reg)
{
        return readl(hsdma->base + reg);
}

static void mtk_dma_write(struct mtk_hsdma_device *hsdma, u32 reg, u32 val)
{
        writel(val, hsdma->base + reg);
}

static void mtk_dma_rmw(struct mtk_hsdma_device *hsdma, u32 reg,
                        u32 mask, u32 set)
{
        u32 val;

        val = mtk_dma_read(hsdma, reg);
        val &= ~mask;
        val |= set;
        mtk_dma_write(hsdma, reg, val);
}

static void mtk_dma_set(struct mtk_hsdma_device *hsdma, u32 reg, u32 val)
{
        mtk_dma_rmw(hsdma, reg, 0, val);
}

static void mtk_dma_clr(struct mtk_hsdma_device *hsdma, u32 reg, u32 val)
{
        mtk_dma_rmw(hsdma, reg, val, 0);
}

static void mtk_hsdma_vdesc_free(struct virt_dma_desc *vd)
{
        kfree(container_of(vd, struct mtk_hsdma_vdesc, vd));
}

static int mtk_hsdma_busy_wait(struct mtk_hsdma_device *hsdma)
{
        u32 status = 0;

        return readl_poll_timeout(hsdma->base + MTK_HSDMA_GLO, status,
                                  !(status & MTK_HSDMA_GLO_BUSY),
                                  MTK_HSDMA_USEC_POLL,
                                  MTK_HSDMA_TIMEOUT_POLL);
}

static int mtk_hsdma_alloc_pchan(struct mtk_hsdma_device *hsdma,
                                 struct mtk_hsdma_pchan *pc)
{
        struct mtk_hsdma_ring *ring = &pc->ring;
        int err;

        memset(pc, 0, sizeof(*pc));

        /*
         * Allocate ring space where [0 ... MTK_DMA_SIZE - 1] is for TX ring
         * and [MTK_DMA_SIZE ... 2 * MTK_DMA_SIZE - 1] is for RX ring.
         */
        pc->sz_ring = 2 * MTK_DMA_SIZE * sizeof(*ring->txd);
        ring->txd = dma_alloc_coherent(hsdma2dev(hsdma), pc->sz_ring,
                                       &ring->tphys, GFP_NOWAIT);
        if (!ring->txd)
                return -ENOMEM;

        ring->rxd = &ring->txd[MTK_DMA_SIZE];
        ring->rphys = ring->tphys + MTK_DMA_SIZE * sizeof(*ring->txd);
        ring->cur_tptr = 0;
        ring->cur_rptr = MTK_DMA_SIZE - 1;

        ring->cb = kcalloc(MTK_DMA_SIZE, sizeof(*ring->cb), GFP_NOWAIT);
        if (!ring->cb) {
                err = -ENOMEM;
                goto err_free_dma;
        }

        atomic_set(&pc->nr_free, MTK_DMA_SIZE - 1);

        /* Disable HSDMA and wait for the completion */
        mtk_dma_clr(hsdma, MTK_HSDMA_GLO, MTK_HSDMA_GLO_DMA);
        err = mtk_hsdma_busy_wait(hsdma);
        if (err)
                goto err_free_cb;

        /* Reset */
        mtk_dma_set(hsdma, MTK_HSDMA_RESET,
                    MTK_HSDMA_RST_TX | MTK_HSDMA_RST_RX);
        mtk_dma_clr(hsdma, MTK_HSDMA_RESET,
                    MTK_HSDMA_RST_TX | MTK_HSDMA_RST_RX);

        /* Setup HSDMA initial pointer in the ring */
        mtk_dma_write(hsdma, MTK_HSDMA_TX_BASE, ring->tphys);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_CNT, MTK_DMA_SIZE);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_CPU, ring->cur_tptr);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_DMA, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_BASE, ring->rphys);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_CNT, MTK_DMA_SIZE);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_CPU, ring->cur_rptr);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_DMA, 0);

        /* Enable HSDMA */
        mtk_dma_set(hsdma, MTK_HSDMA_GLO, MTK_HSDMA_GLO_DMA);

        /* Setup delayed interrupt */
        mtk_dma_write(hsdma, MTK_HSDMA_DLYINT, MTK_HSDMA_DLYINT_DEFAULT);

        /* Enable interrupt */
        mtk_dma_set(hsdma, MTK_HSDMA_INT_ENABLE, MTK_HSDMA_INT_RXDONE);

        return 0;

err_free_cb:
        kfree(ring->cb);

err_free_dma:
        dma_free_coherent(hsdma2dev(hsdma),
                          pc->sz_ring, ring->txd, ring->tphys);
        return err;
}

static void mtk_hsdma_free_pchan(struct mtk_hsdma_device *hsdma,
                                 struct mtk_hsdma_pchan *pc)
{
        struct mtk_hsdma_ring *ring = &pc->ring;

        /* Disable HSDMA and then wait for the completion */
        mtk_dma_clr(hsdma, MTK_HSDMA_GLO, MTK_HSDMA_GLO_DMA);
        mtk_hsdma_busy_wait(hsdma);

        /* Reset pointer in the ring */
        mtk_dma_clr(hsdma, MTK_HSDMA_INT_ENABLE, MTK_HSDMA_INT_RXDONE);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_BASE, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_CNT, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_TX_CPU, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_BASE, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_CNT, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_RX_CPU, MTK_DMA_SIZE - 1);

        kfree(ring->cb);

        dma_free_coherent(hsdma2dev(hsdma),
                          pc->sz_ring, ring->txd, ring->tphys);
}

static int mtk_hsdma_issue_pending_vdesc(struct mtk_hsdma_device *hsdma,
                                         struct mtk_hsdma_pchan *pc,
                                         struct mtk_hsdma_vdesc *hvd)
{
        struct mtk_hsdma_ring *ring = &pc->ring;
        struct mtk_hsdma_pdesc *txd, *rxd;
        u16 reserved, prev, tlen, num_sgs;
        unsigned long flags;

        /* Protect against PC is accessed by multiple VCs simultaneously */
        spin_lock_irqsave(&hsdma->lock, flags);

        /*
         * Reserve rooms, where pc->nr_free is used to track how many free
         * rooms in the ring being updated in user and IRQ context.
         */
        num_sgs = DIV_ROUND_UP(hvd->len, MTK_HSDMA_MAX_LEN);
        reserved = min_t(u16, num_sgs, atomic_read(&pc->nr_free));

        if (!reserved) {
                spin_unlock_irqrestore(&hsdma->lock, flags);
                return -ENOSPC;
        }

        atomic_sub(reserved, &pc->nr_free);

        while (reserved--) {
                /* Limit size by PD capability for valid data moving */
                tlen = (hvd->len > MTK_HSDMA_MAX_LEN) ?
                       MTK_HSDMA_MAX_LEN : hvd->len;

                /*
                 * Setup PDs using the remaining VD info mapped on those
                 * reserved rooms. And since RXD is shared memory between the
                 * host and the device allocated by dma_alloc_coherent call,
                 * the helper macro WRITE_ONCE can ensure the data written to
                 * RAM would really happens.
                 */
                txd = &ring->txd[ring->cur_tptr];
                WRITE_ONCE(txd->desc1, hvd->src);
                WRITE_ONCE(txd->desc2,
                           hsdma->soc->ls0 | MTK_HSDMA_DESC_PLEN(tlen));

                rxd = &ring->rxd[ring->cur_tptr];
                WRITE_ONCE(rxd->desc1, hvd->dest);
                WRITE_ONCE(rxd->desc2, MTK_HSDMA_DESC_PLEN(tlen));

                /* Associate VD, the PD belonged to */
                ring->cb[ring->cur_tptr].vd = &hvd->vd;

                /* Move forward the pointer of TX ring */
                ring->cur_tptr = MTK_HSDMA_NEXT_DESP_IDX(ring->cur_tptr,
                                                         MTK_DMA_SIZE);

                /* Update VD with remaining data */
                hvd->src  += tlen;
                hvd->dest += tlen;
                hvd->len  -= tlen;
        }

        /*
         * Tagging flag for the last PD for VD will be responsible for
         * completing VD.
         */
        if (!hvd->len) {
                prev = MTK_HSDMA_LAST_DESP_IDX(ring->cur_tptr, MTK_DMA_SIZE);
                ring->cb[prev].flag = MTK_HSDMA_VDESC_FINISHED;
        }

        /* Ensure all changes indeed done before we're going on */
        wmb();

        /*
         * Updating into hardware the pointer of TX ring lets HSDMA to take
         * action for those pending PDs.
         */
        mtk_dma_write(hsdma, MTK_HSDMA_TX_CPU, ring->cur_tptr);

        spin_unlock_irqrestore(&hsdma->lock, flags);

        return 0;
}

static void mtk_hsdma_issue_vchan_pending(struct mtk_hsdma_device *hsdma,
                                          struct mtk_hsdma_vchan *hvc)
{
        struct virt_dma_desc *vd, *vd2;
        int err;

        lockdep_assert_held(&hvc->vc.lock);

        list_for_each_entry_safe(vd, vd2, &hvc->vc.desc_issued, node) {
                struct mtk_hsdma_vdesc *hvd;

                hvd = to_hsdma_vdesc(vd);

                /* Map VD into PC and all VCs shares a single PC */
                err = mtk_hsdma_issue_pending_vdesc(hsdma, hsdma->pc, hvd);

                /*
                 * Move VD from desc_issued to desc_hw_processing when entire
                 * VD is fit into available PDs. Otherwise, the uncompleted
                 * VDs would stay in list desc_issued and then restart the
                 * processing as soon as possible once underlying ring space
                 * got freed.
                 */
                if (err == -ENOSPC || hvd->len > 0)
                        break;

                /*
                 * The extra list desc_hw_processing is used because
                 * hardware can't provide sufficient information allowing us
                 * to know what VDs are still working on the underlying ring.
                 * Through the additional list, it can help us to implement
                 * terminate_all, residue calculation and such thing needed
                 * to know detail descriptor status on the hardware.
                 */
                list_move_tail(&vd->node, &hvc->desc_hw_processing);
        }
}

static void mtk_hsdma_free_rooms_in_ring(struct mtk_hsdma_device *hsdma)
{
        struct mtk_hsdma_vchan *hvc;
        struct mtk_hsdma_pdesc *rxd;
        struct mtk_hsdma_vdesc *hvd;
        struct mtk_hsdma_pchan *pc;
        struct mtk_hsdma_cb *cb;
        int i = MTK_DMA_SIZE;
        __le32 desc2;
        u32 status;
        u16 next;

        /* Read IRQ status */
        status = mtk_dma_read(hsdma, MTK_HSDMA_INT_STATUS);
        if (unlikely(!(status & MTK_HSDMA_INT_RXDONE)))
                goto rx_done;

        pc = hsdma->pc;

        /*
         * Using a fail-safe loop with iterations of up to MTK_DMA_SIZE to
         * reclaim these finished descriptors: The most number of PDs the ISR
         * can handle at one time shouldn't be more than MTK_DMA_SIZE so we
         * take it as limited count instead of just using a dangerous infinite
         * poll.
         */
        while (i--) {
                next = MTK_HSDMA_NEXT_DESP_IDX(pc->ring.cur_rptr,
                                               MTK_DMA_SIZE);
                rxd = &pc->ring.rxd[next];

                /*
                 * If MTK_HSDMA_DESC_DDONE is no specified, that means data
                 * moving for the PD is still under going.
                 */
                desc2 = READ_ONCE(rxd->desc2);
                if (!(desc2 & hsdma->soc->ddone))
                        break;

                cb = &pc->ring.cb[next];
                if (unlikely(!cb->vd)) {
                        dev_err(hsdma2dev(hsdma), "cb->vd cannot be null\n");
                        break;
                }

                /* Update residue of VD the associated PD belonged to */
                hvd = to_hsdma_vdesc(cb->vd);
                hvd->residue -= MTK_HSDMA_DESC_PLEN_GET(rxd->desc2);

                /* Complete VD until the relevant last PD is finished */
                if (IS_MTK_HSDMA_VDESC_FINISHED(cb->flag)) {
                        hvc = to_hsdma_vchan(cb->vd->tx.chan);

                        spin_lock(&hvc->vc.lock);

                        /* Remove VD from list desc_hw_processing */
                        list_del(&cb->vd->node);

                        /* Add VD into list desc_completed */
                        vchan_cookie_complete(cb->vd);

                        if (hvc->issue_synchronize &&
                            list_empty(&hvc->desc_hw_processing)) {
                                complete(&hvc->issue_completion);
                                hvc->issue_synchronize = false;
                        }
                        spin_unlock(&hvc->vc.lock);

                        cb->flag = 0;
                }

                cb->vd = 0;

                /*
                 * Recycle the RXD with the helper WRITE_ONCE that can ensure
                 * data written into RAM would really happens.
                 */
                WRITE_ONCE(rxd->desc1, 0);
                WRITE_ONCE(rxd->desc2, 0);
                pc->ring.cur_rptr = next;

                /* Release rooms */
                atomic_inc(&pc->nr_free);
        }

        /* Ensure all changes indeed done before we're going on */
        wmb();

        /* Update CPU pointer for those completed PDs */
        mtk_dma_write(hsdma, MTK_HSDMA_RX_CPU, pc->ring.cur_rptr);

        /*
         * Acking the pending IRQ allows hardware no longer to keep the used
         * IRQ line in certain trigger state when software has completed all
         * the finished physical descriptors.
         */
        if (atomic_read(&pc->nr_free) >= MTK_DMA_SIZE - 1)
                mtk_dma_write(hsdma, MTK_HSDMA_INT_STATUS, status);

        /* ASAP handles pending VDs in all VCs after freeing some rooms */
        for (i = 0; i < hsdma->dma_requests; i++) {
                hvc = &hsdma->vc[i];
                spin_lock(&hvc->vc.lock);
                mtk_hsdma_issue_vchan_pending(hsdma, hvc);
                spin_unlock(&hvc->vc.lock);
        }

rx_done:
        /* All completed PDs are cleaned up, so enable interrupt again */
        mtk_dma_set(hsdma, MTK_HSDMA_INT_ENABLE, MTK_HSDMA_INT_RXDONE);
}

static irqreturn_t mtk_hsdma_irq(int irq, void *devid)
{
        struct mtk_hsdma_device *hsdma = devid;

        /*
         * Disable interrupt until all completed PDs are cleaned up in
         * mtk_hsdma_free_rooms call.
         */
        mtk_dma_clr(hsdma, MTK_HSDMA_INT_ENABLE, MTK_HSDMA_INT_RXDONE);

        mtk_hsdma_free_rooms_in_ring(hsdma);

        return IRQ_HANDLED;
}

static struct virt_dma_desc *mtk_hsdma_find_active_desc(struct dma_chan *c,
                                                        dma_cookie_t cookie)
{
        struct mtk_hsdma_vchan *hvc = to_hsdma_vchan(c);
        struct virt_dma_desc *vd;

        list_for_each_entry(vd, &hvc->desc_hw_processing, node)
                if (vd->tx.cookie == cookie)
                        return vd;

        list_for_each_entry(vd, &hvc->vc.desc_issued, node)
                if (vd->tx.cookie == cookie)
                        return vd;

        return NULL;
}

static enum dma_status mtk_hsdma_tx_status(struct dma_chan *c,
                                           dma_cookie_t cookie,
                                           struct dma_tx_state *txstate)
{
        struct mtk_hsdma_vchan *hvc = to_hsdma_vchan(c);
        struct mtk_hsdma_vdesc *hvd;
        struct virt_dma_desc *vd;
        enum dma_status ret;
        unsigned long flags;
        size_t bytes = 0;

        ret = dma_cookie_status(c, cookie, txstate);
        if (ret == DMA_COMPLETE || !txstate)
                return ret;

        spin_lock_irqsave(&hvc->vc.lock, flags);
        vd = mtk_hsdma_find_active_desc(c, cookie);
        spin_unlock_irqrestore(&hvc->vc.lock, flags);

        if (vd) {
                hvd = to_hsdma_vdesc(vd);
                bytes = hvd->residue;
        }

        dma_set_residue(txstate, bytes);

        return ret;
}

static void mtk_hsdma_issue_pending(struct dma_chan *c)
{
        struct mtk_hsdma_device *hsdma = to_hsdma_dev(c);
        struct mtk_hsdma_vchan *hvc = to_hsdma_vchan(c);
        unsigned long flags;

        spin_lock_irqsave(&hvc->vc.lock, flags);

        if (vchan_issue_pending(&hvc->vc))
                mtk_hsdma_issue_vchan_pending(hsdma, hvc);

        spin_unlock_irqrestore(&hvc->vc.lock, flags);
}

static struct dma_async_tx_descriptor *
mtk_hsdma_prep_dma_memcpy(struct dma_chan *c, dma_addr_t dest,
                          dma_addr_t src, size_t len, unsigned long flags)
{
        struct mtk_hsdma_vdesc *hvd;

        hvd = kzalloc(sizeof(*hvd), GFP_NOWAIT);
        if (!hvd)
                return NULL;

        hvd->len = len;
        hvd->residue = len;
        hvd->src = src;
        hvd->dest = dest;

        return vchan_tx_prep(to_virt_chan(c), &hvd->vd, flags);
}

static int mtk_hsdma_free_inactive_desc(struct dma_chan *c)
{
        struct virt_dma_chan *vc = to_virt_chan(c);
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&vc->lock, flags);
        list_splice_tail_init(&vc->desc_allocated, &head);
        list_splice_tail_init(&vc->desc_submitted, &head);
        list_splice_tail_init(&vc->desc_issued, &head);
        spin_unlock_irqrestore(&vc->lock, flags);

        /* At the point, we don't expect users put descriptor into VC again */
        vchan_dma_desc_free_list(vc, &head);

        return 0;
}

static void mtk_hsdma_free_active_desc(struct dma_chan *c)
{
        struct mtk_hsdma_vchan *hvc = to_hsdma_vchan(c);
        bool sync_needed = false;

        /*
         * Once issue_synchronize is being set, which means once the hardware
         * consumes all descriptors for the channel in the ring, the
         * synchronization must be be notified immediately it is completed.
         */
        spin_lock(&hvc->vc.lock);
        if (!list_empty(&hvc->desc_hw_processing)) {
                hvc->issue_synchronize = true;
                sync_needed = true;
        }
        spin_unlock(&hvc->vc.lock);

        if (sync_needed)
                wait_for_completion(&hvc->issue_completion);
        /*
         * At the point, we expect that all remaining descriptors in the ring
         * for the channel should be all processing done.
         */
        WARN_ONCE(!list_empty(&hvc->desc_hw_processing),
                  "Desc pending still in list desc_hw_processing\n");

        /* Free all descriptors in list desc_completed */
        vchan_synchronize(&hvc->vc);

        WARN_ONCE(!list_empty(&hvc->vc.desc_completed),
                  "Desc pending still in list desc_completed\n");
}

static int mtk_hsdma_terminate_all(struct dma_chan *c)
{
        /*
         * Free pending descriptors not processed yet by hardware that have
         * previously been submitted to the channel.
         */
        mtk_hsdma_free_inactive_desc(c);

        /*
         * However, the DMA engine doesn't provide any way to stop these
         * descriptors being processed currently by hardware. The only way is
         * to just waiting until these descriptors are all processed completely
         * through mtk_hsdma_free_active_desc call.
         */
        mtk_hsdma_free_active_desc(c);

        return 0;
}

static int mtk_hsdma_alloc_chan_resources(struct dma_chan *c)
{
        struct mtk_hsdma_device *hsdma = to_hsdma_dev(c);
        int err;

        /*
         * Since HSDMA has only one PC, the resource for PC is being allocated
         * when the first VC is being created and the other VCs would run on
         * the same PC.
         */
        if (!refcount_read(&hsdma->pc_refcnt)) {
                err = mtk_hsdma_alloc_pchan(hsdma, hsdma->pc);
                if (err)
                        return err;
                /*
                 * refcount_inc would complain increment on 0; use-after-free.
                 * Thus, we need to explicitly set it as 1 initially.
                 */
                refcount_set(&hsdma->pc_refcnt, 1);
        } else {
                refcount_inc(&hsdma->pc_refcnt);
        }

        return 0;
}

static void mtk_hsdma_free_chan_resources(struct dma_chan *c)
{
        struct mtk_hsdma_device *hsdma = to_hsdma_dev(c);

        /* Free all descriptors in all lists on the VC */
        mtk_hsdma_terminate_all(c);

        /* The resource for PC is not freed until all the VCs are destroyed */
        if (!refcount_dec_and_test(&hsdma->pc_refcnt))
                return;

        mtk_hsdma_free_pchan(hsdma, hsdma->pc);
}

static int mtk_hsdma_hw_init(struct mtk_hsdma_device *hsdma)
{
        int err;

        pm_runtime_enable(hsdma2dev(hsdma));
        pm_runtime_get_sync(hsdma2dev(hsdma));

        err = clk_prepare_enable(hsdma->clk);
        if (err)
                return err;

        mtk_dma_write(hsdma, MTK_HSDMA_INT_ENABLE, 0);
        mtk_dma_write(hsdma, MTK_HSDMA_GLO, MTK_HSDMA_GLO_DEFAULT);

        return 0;
}

static int mtk_hsdma_hw_deinit(struct mtk_hsdma_device *hsdma)
{
        mtk_dma_write(hsdma, MTK_HSDMA_GLO, 0);

        clk_disable_unprepare(hsdma->clk);

        pm_runtime_put_sync(hsdma2dev(hsdma));
        pm_runtime_disable(hsdma2dev(hsdma));

        return 0;
}

static const struct mtk_hsdma_soc mt7623_soc = {
        .ddone = BIT(31),
        .ls0 = BIT(30),
};

static const struct mtk_hsdma_soc mt7622_soc = {
        .ddone = BIT(15),
        .ls0 = BIT(14),
};

static const struct of_device_id mtk_hsdma_match[] = {
        { .compatible = "mediatek,mt7623-hsdma", .data = &mt7623_soc},
        { .compatible = "mediatek,mt7622-hsdma", .data = &mt7622_soc},
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mtk_hsdma_match);

static int mtk_hsdma_probe(struct platform_device *pdev)
{
        struct mtk_hsdma_device *hsdma;
        struct mtk_hsdma_vchan *vc;
        struct dma_device *dd;
        struct resource *res;
        int i, err;

        hsdma = devm_kzalloc(&pdev->dev, sizeof(*hsdma), GFP_KERNEL);
        if (!hsdma)
                return -ENOMEM;

        dd = &hsdma->ddev;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        hsdma->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(hsdma->base))
                return PTR_ERR(hsdma->base);

        hsdma->soc = of_device_get_match_data(&pdev->dev);
        if (!hsdma->soc) {
                dev_err(&pdev->dev, "No device match found\n");
                return -ENODEV;
        }

        hsdma->clk = devm_clk_get(&pdev->dev, "hsdma");
        if (IS_ERR(hsdma->clk)) {
                dev_err(&pdev->dev, "No clock for %s\n",
                        dev_name(&pdev->dev));
                return PTR_ERR(hsdma->clk);
        }

        res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (!res) {
                dev_err(&pdev->dev, "No irq resource for %s\n",
                        dev_name(&pdev->dev));
                return -EINVAL;
        }
        hsdma->irq = res->start;

        refcount_set(&hsdma->pc_refcnt, 0);
        spin_lock_init(&hsdma->lock);

        dma_cap_set(DMA_MEMCPY, dd->cap_mask);

        dd->copy_align = MTK_HSDMA_ALIGN_SIZE;
        dd->device_alloc_chan_resources = mtk_hsdma_alloc_chan_resources;
        dd->device_free_chan_resources = mtk_hsdma_free_chan_resources;
        dd->device_tx_status = mtk_hsdma_tx_status;
        dd->device_issue_pending = mtk_hsdma_issue_pending;
        dd->device_prep_dma_memcpy = mtk_hsdma_prep_dma_memcpy;
        dd->device_terminate_all = mtk_hsdma_terminate_all;
        dd->src_addr_widths = MTK_HSDMA_DMA_BUSWIDTHS;
        dd->dst_addr_widths = MTK_HSDMA_DMA_BUSWIDTHS;
        dd->directions = BIT(DMA_MEM_TO_MEM);
        dd->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
        dd->dev = &pdev->dev;
        INIT_LIST_HEAD(&dd->channels);

        hsdma->dma_requests = MTK_HSDMA_NR_VCHANS;
        if (pdev->dev.of_node && of_property_read_u32(pdev->dev.of_node,
                                                      "dma-requests",
                                                      &hsdma->dma_requests)) {
                dev_info(&pdev->dev,
                         "Using %u as missing dma-requests property\n",
                         MTK_HSDMA_NR_VCHANS);
        }

        hsdma->pc = devm_kcalloc(&pdev->dev, MTK_HSDMA_NR_MAX_PCHANS,
                                 sizeof(*hsdma->pc), GFP_KERNEL);
        if (!hsdma->pc)
                return -ENOMEM;

        hsdma->vc = devm_kcalloc(&pdev->dev, hsdma->dma_requests,
                                 sizeof(*hsdma->vc), GFP_KERNEL);
        if (!hsdma->vc)
                return -ENOMEM;

        for (i = 0; i < hsdma->dma_requests; i++) {
                vc = &hsdma->vc[i];
                vc->vc.desc_free = mtk_hsdma_vdesc_free;
                vchan_init(&vc->vc, dd);
                init_completion(&vc->issue_completion);
                INIT_LIST_HEAD(&vc->desc_hw_processing);
        }

        err = dma_async_device_register(dd);
        if (err)
                return err;

        err = of_dma_controller_register(pdev->dev.of_node,
                                         of_dma_xlate_by_chan_id, hsdma);
        if (err) {
                dev_err(&pdev->dev,
                        "MediaTek HSDMA OF registration failed %d\n", err);
                goto err_unregister;
        }

        mtk_hsdma_hw_init(hsdma);

        err = devm_request_irq(&pdev->dev, hsdma->irq,
                               mtk_hsdma_irq, 0,
                               dev_name(&pdev->dev), hsdma);
        if (err) {
                dev_err(&pdev->dev,
                        "request_irq failed with err %d\n", err);
                goto err_free;

        }

        platform_set_drvdata(pdev, hsdma);

        dev_info(&pdev->dev, "MediaTek HSDMA driver registered\n");

        return 0;

err_free:
        of_dma_controller_free(pdev->dev.of_node);
err_unregister:
        dma_async_device_unregister(dd);

        return err;
}

static int mtk_hsdma_remove(struct platform_device *pdev)
{
        struct mtk_hsdma_device *hsdma = platform_get_drvdata(pdev);
        struct mtk_hsdma_vchan *vc;
        int i;

        /* Kill VC task */
        for (i = 0; i < hsdma->dma_requests; i++) {
                vc = &hsdma->vc[i];

                list_del(&vc->vc.chan.device_node);
                tasklet_kill(&vc->vc.task);
        }

        /* Disable DMA interrupt */
        mtk_dma_write(hsdma, MTK_HSDMA_INT_ENABLE, 0);

        /* Waits for any pending IRQ handlers to complete */
        synchronize_irq(hsdma->irq);

        /* Disable hardware */
        mtk_hsdma_hw_deinit(hsdma);

        dma_async_device_unregister(&hsdma->ddev);
        of_dma_controller_free(pdev->dev.of_node);

        return 0;
}

static struct platform_driver mtk_hsdma_driver = {
        .probe          = mtk_hsdma_probe,
        .remove         = mtk_hsdma_remove,
        .driver = {
                .name           = KBUILD_MODNAME,
                .of_match_table = mtk_hsdma_match,
        },
};
module_platform_driver(mtk_hsdma_driver);

MODULE_DESCRIPTION("MediaTek High-Speed DMA Controller Driver");
MODULE_AUTHOR("Sean Wang <sean.wang@mediatek.com>");
MODULE_LICENSE("GPL v2");