Merge tag 'gpio-v3.13-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[linux-2.6.git] / drivers / dma / s3c24xx-dma.c

/*
 * S3C24XX DMA handling
 *
 * Copyright (c) 2013 Heiko Stuebner <heiko@sntech.de>
 *
 * based on amba-pl08x.c
 *
 * Copyright (c) 2006 ARM Ltd.
 * Copyright (c) 2010 ST-Ericsson SA
 *
 * Author: Peter Pearse <peter.pearse@arm.com>
 * Author: Linus Walleij <linus.walleij@stericsson.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * The DMA controllers in S3C24XX SoCs have a varying number of DMA signals
 * that can be routed to any of the 4 to 8 hardware-channels.
 *
 * Therefore on these DMA controllers the number of channels
 * and the number of incoming DMA signals are two totally different things.
 * It is usually not possible to theoretically handle all physical signals,
 * so a multiplexing scheme with possible denial of use is necessary.
 *
 * Open items:
 * - bursts
 */

#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/clk.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/platform_data/dma-s3c24xx.h>

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

#define MAX_DMA_CHANNELS        8

#define S3C24XX_DISRC                   0x00
#define S3C24XX_DISRCC                  0x04
#define S3C24XX_DISRCC_INC_INCREMENT    0
#define S3C24XX_DISRCC_INC_FIXED        BIT(0)
#define S3C24XX_DISRCC_LOC_AHB          0
#define S3C24XX_DISRCC_LOC_APB          BIT(1)

#define S3C24XX_DIDST                   0x08
#define S3C24XX_DIDSTC                  0x0c
#define S3C24XX_DIDSTC_INC_INCREMENT    0
#define S3C24XX_DIDSTC_INC_FIXED        BIT(0)
#define S3C24XX_DIDSTC_LOC_AHB          0
#define S3C24XX_DIDSTC_LOC_APB          BIT(1)
#define S3C24XX_DIDSTC_INT_TC0          0
#define S3C24XX_DIDSTC_INT_RELOAD       BIT(2)

#define S3C24XX_DCON                    0x10

#define S3C24XX_DCON_TC_MASK            0xfffff
#define S3C24XX_DCON_DSZ_BYTE           (0 << 20)
#define S3C24XX_DCON_DSZ_HALFWORD       (1 << 20)
#define S3C24XX_DCON_DSZ_WORD           (2 << 20)
#define S3C24XX_DCON_DSZ_MASK           (3 << 20)
#define S3C24XX_DCON_DSZ_SHIFT          20
#define S3C24XX_DCON_AUTORELOAD         0
#define S3C24XX_DCON_NORELOAD           BIT(22)
#define S3C24XX_DCON_HWTRIG             BIT(23)
#define S3C24XX_DCON_HWSRC_SHIFT        24
#define S3C24XX_DCON_SERV_SINGLE        0
#define S3C24XX_DCON_SERV_WHOLE         BIT(27)
#define S3C24XX_DCON_TSZ_UNIT           0
#define S3C24XX_DCON_TSZ_BURST4         BIT(28)
#define S3C24XX_DCON_INT                BIT(29)
#define S3C24XX_DCON_SYNC_PCLK          0
#define S3C24XX_DCON_SYNC_HCLK          BIT(30)
#define S3C24XX_DCON_DEMAND             0
#define S3C24XX_DCON_HANDSHAKE          BIT(31)

#define S3C24XX_DSTAT                   0x14
#define S3C24XX_DSTAT_STAT_BUSY         BIT(20)
#define S3C24XX_DSTAT_CURRTC_MASK       0xfffff

#define S3C24XX_DMASKTRIG               0x20
#define S3C24XX_DMASKTRIG_SWTRIG        BIT(0)
#define S3C24XX_DMASKTRIG_ON            BIT(1)
#define S3C24XX_DMASKTRIG_STOP          BIT(2)

#define S3C24XX_DMAREQSEL               0x24
#define S3C24XX_DMAREQSEL_HW            BIT(0)

/*
 * S3C2410, S3C2440 and S3C2442 SoCs cannot select any physical channel
 * for a DMA source. Instead only specific channels are valid.
 * All of these SoCs have 4 physical channels and the number of request
 * source bits is 3. Additionally we also need 1 bit to mark the channel
 * as valid.
 * Therefore we separate the chansel element of the channel data into 4
 * parts of 4 bits each, to hold the information if the channel is valid
 * and the hw request source to use.
 *
 * Example:
 * SDI is valid on channels 0, 2 and 3 - with varying hw request sources.
 * For it the chansel field would look like
 *
 * ((BIT(3) | 1) << 3 * 4) | // channel 3, with request source 1
 * ((BIT(3) | 2) << 2 * 4) | // channel 2, with request source 2
 * ((BIT(3) | 2) << 0 * 4)   // channel 0, with request source 2
 */
#define S3C24XX_CHANSEL_WIDTH           4
#define S3C24XX_CHANSEL_VALID           BIT(3)
#define S3C24XX_CHANSEL_REQ_MASK        7

/*
 * struct soc_data - vendor-specific config parameters for individual SoCs
 * @stride: spacing between the registers of each channel
 * @has_reqsel: does the controller use the newer requestselection mechanism
 * @has_clocks: are controllable dma-clocks present
 */
struct soc_data {
        int stride;
        bool has_reqsel;
        bool has_clocks;
};

/*
 * enum s3c24xx_dma_chan_state - holds the virtual channel states
 * @S3C24XX_DMA_CHAN_IDLE: the channel is idle
 * @S3C24XX_DMA_CHAN_RUNNING: the channel has allocated a physical transport
 * channel and is running a transfer on it
 * @S3C24XX_DMA_CHAN_WAITING: the channel is waiting for a physical transport
 * channel to become available (only pertains to memcpy channels)
 */
enum s3c24xx_dma_chan_state {
        S3C24XX_DMA_CHAN_IDLE,
        S3C24XX_DMA_CHAN_RUNNING,
        S3C24XX_DMA_CHAN_WAITING,
};

/*
 * struct s3c24xx_sg - structure containing data per sg
 * @src_addr: src address of sg
 * @dst_addr: dst address of sg
 * @len: transfer len in bytes
 * @node: node for txd's dsg_list
 */
struct s3c24xx_sg {
        dma_addr_t src_addr;
        dma_addr_t dst_addr;
        size_t len;
        struct list_head node;
};

/*
 * struct s3c24xx_txd - wrapper for struct dma_async_tx_descriptor
 * @vd: virtual DMA descriptor
 * @dsg_list: list of children sg's
 * @at: sg currently being transfered
 * @width: transfer width
 * @disrcc: value for source control register
 * @didstc: value for destination control register
 * @dcon: base value for dcon register
 */
struct s3c24xx_txd {
        struct virt_dma_desc vd;
        struct list_head dsg_list;
        struct list_head *at;
        u8 width;
        u32 disrcc;
        u32 didstc;
        u32 dcon;
};

struct s3c24xx_dma_chan;

/*
 * struct s3c24xx_dma_phy - holder for the physical channels
 * @id: physical index to this channel
 * @valid: does the channel have all required elements
 * @base: virtual memory base (remapped) for the this channel
 * @irq: interrupt for this channel
 * @clk: clock for this channel
 * @lock: a lock to use when altering an instance of this struct
 * @serving: virtual channel currently being served by this physicalchannel
 * @host: a pointer to the host (internal use)
 */
struct s3c24xx_dma_phy {
        unsigned int                    id;
        bool                            valid;
        void __iomem                    *base;
        unsigned int                    irq;
        struct clk                      *clk;
        spinlock_t                      lock;
        struct s3c24xx_dma_chan         *serving;
        struct s3c24xx_dma_engine       *host;
};

/*
 * struct s3c24xx_dma_chan - this structure wraps a DMA ENGINE channel
 * @id: the id of the channel
 * @name: name of the channel
 * @vc: wrappped virtual channel
 * @phy: the physical channel utilized by this channel, if there is one
 * @runtime_addr: address for RX/TX according to the runtime config
 * @at: active transaction on this channel
 * @lock: a lock for this channel data
 * @host: a pointer to the host (internal use)
 * @state: whether the channel is idle, running etc
 * @slave: whether this channel is a device (slave) or for memcpy
 */
struct s3c24xx_dma_chan {
        int id;
        const char *name;
        struct virt_dma_chan vc;
        struct s3c24xx_dma_phy *phy;
        struct dma_slave_config cfg;
        struct s3c24xx_txd *at;
        struct s3c24xx_dma_engine *host;
        enum s3c24xx_dma_chan_state state;
        bool slave;
};

/*
 * struct s3c24xx_dma_engine - the local state holder for the S3C24XX
 * @pdev: the corresponding platform device
 * @pdata: platform data passed in from the platform/machine
 * @base: virtual memory base (remapped)
 * @slave: slave engine for this instance
 * @memcpy: memcpy engine for this instance
 * @phy_chans: array of data for the physical channels
 */
struct s3c24xx_dma_engine {
        struct platform_device                  *pdev;
        const struct s3c24xx_dma_platdata       *pdata;
        struct soc_data                         *sdata;
        void __iomem                            *base;
        struct dma_device                       slave;
        struct dma_device                       memcpy;
        struct s3c24xx_dma_phy                  *phy_chans;
};

/*
 * Physical channel handling
 */

/*
 * Check whether a certain channel is busy or not.
 */
static int s3c24xx_dma_phy_busy(struct s3c24xx_dma_phy *phy)
{
        unsigned int val = readl(phy->base + S3C24XX_DSTAT);
        return val & S3C24XX_DSTAT_STAT_BUSY;
}

static bool s3c24xx_dma_phy_valid(struct s3c24xx_dma_chan *s3cchan,
                                  struct s3c24xx_dma_phy *phy)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        const struct s3c24xx_dma_platdata *pdata = s3cdma->pdata;
        struct s3c24xx_dma_channel *cdata = &pdata->channels[s3cchan->id];
        int phyvalid;

        /* every phy is valid for memcopy channels */
        if (!s3cchan->slave)
                return true;

        /* On newer variants all phys can be used for all virtual channels */
        if (s3cdma->sdata->has_reqsel)
                return true;

        phyvalid = (cdata->chansel >> (phy->id * S3C24XX_CHANSEL_WIDTH));
        return (phyvalid & S3C24XX_CHANSEL_VALID) ? true : false;
}

/*
 * Allocate a physical channel for a virtual channel
 *
 * Try to locate a physical channel to be used for this transfer. If all
 * are taken return NULL and the requester will have to cope by using
 * some fallback PIO mode or retrying later.
 */
static
struct s3c24xx_dma_phy *s3c24xx_dma_get_phy(struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        const struct s3c24xx_dma_platdata *pdata = s3cdma->pdata;
        struct s3c24xx_dma_channel *cdata;
        struct s3c24xx_dma_phy *phy = NULL;
        unsigned long flags;
        int i;
        int ret;

        if (s3cchan->slave)
                cdata = &pdata->channels[s3cchan->id];

        for (i = 0; i < s3cdma->pdata->num_phy_channels; i++) {
                phy = &s3cdma->phy_chans[i];

                if (!phy->valid)
                        continue;

                if (!s3c24xx_dma_phy_valid(s3cchan, phy))
                        continue;

                spin_lock_irqsave(&phy->lock, flags);

                if (!phy->serving) {
                        phy->serving = s3cchan;
                        spin_unlock_irqrestore(&phy->lock, flags);
                        break;
                }

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

        /* No physical channel available, cope with it */
        if (i == s3cdma->pdata->num_phy_channels) {
                dev_warn(&s3cdma->pdev->dev, "no phy channel available\n");
                return NULL;
        }

        /* start the phy clock */
        if (s3cdma->sdata->has_clocks) {
                ret = clk_enable(phy->clk);
                if (ret) {
                        dev_err(&s3cdma->pdev->dev, "could not enable clock for channel %d, err %d\n",
                                phy->id, ret);
                        phy->serving = NULL;
                        return NULL;
                }
        }

        return phy;
}

/*
 * Mark the physical channel as free.
 *
 * This drops the link between the physical and virtual channel.
 */
static inline void s3c24xx_dma_put_phy(struct s3c24xx_dma_phy *phy)
{
        struct s3c24xx_dma_engine *s3cdma = phy->host;

        if (s3cdma->sdata->has_clocks)
                clk_disable(phy->clk);

        phy->serving = NULL;
}

/*
 * Stops the channel by writing the stop bit.
 * This should not be used for an on-going transfer, but as a method of
 * shutting down a channel (eg, when it's no longer used) or terminating a
 * transfer.
 */
static void s3c24xx_dma_terminate_phy(struct s3c24xx_dma_phy *phy)
{
        writel(S3C24XX_DMASKTRIG_STOP, phy->base + S3C24XX_DMASKTRIG);
}

/*
 * Virtual channel handling
 */

static inline
struct s3c24xx_dma_chan *to_s3c24xx_dma_chan(struct dma_chan *chan)
{
        return container_of(chan, struct s3c24xx_dma_chan, vc.chan);
}

static u32 s3c24xx_dma_getbytes_chan(struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_phy *phy = s3cchan->phy;
        struct s3c24xx_txd *txd = s3cchan->at;
        u32 tc = readl(phy->base + S3C24XX_DSTAT) & S3C24XX_DSTAT_CURRTC_MASK;

        return tc * txd->width;
}

static int s3c24xx_dma_set_runtime_config(struct s3c24xx_dma_chan *s3cchan,
                                  struct dma_slave_config *config)
{
        if (!s3cchan->slave)
                return -EINVAL;

        /* Reject definitely invalid configurations */
        if (config->src_addr_width == DMA_SLAVE_BUSWIDTH_8_BYTES ||
            config->dst_addr_width == DMA_SLAVE_BUSWIDTH_8_BYTES)
                return -EINVAL;

        s3cchan->cfg = *config;

        return 0;
}

/*
 * Transfer handling
 */

static inline
struct s3c24xx_txd *to_s3c24xx_txd(struct dma_async_tx_descriptor *tx)
{
        return container_of(tx, struct s3c24xx_txd, vd.tx);
}

static struct s3c24xx_txd *s3c24xx_dma_get_txd(void)
{
        struct s3c24xx_txd *txd = kzalloc(sizeof(*txd), GFP_NOWAIT);

        if (txd) {
                INIT_LIST_HEAD(&txd->dsg_list);
                txd->dcon = S3C24XX_DCON_INT | S3C24XX_DCON_NORELOAD;
        }

        return txd;
}

static void s3c24xx_dma_free_txd(struct s3c24xx_txd *txd)
{
        struct s3c24xx_sg *dsg, *_dsg;

        list_for_each_entry_safe(dsg, _dsg, &txd->dsg_list, node) {
                list_del(&dsg->node);
                kfree(dsg);
        }

        kfree(txd);
}

static void s3c24xx_dma_start_next_sg(struct s3c24xx_dma_chan *s3cchan,
                                       struct s3c24xx_txd *txd)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        struct s3c24xx_dma_phy *phy = s3cchan->phy;
        const struct s3c24xx_dma_platdata *pdata = s3cdma->pdata;
        struct s3c24xx_sg *dsg = list_entry(txd->at, struct s3c24xx_sg, node);
        u32 dcon = txd->dcon;
        u32 val;

        /* transfer-size and -count from len and width */
        switch (txd->width) {
        case 1:
                dcon |= S3C24XX_DCON_DSZ_BYTE | dsg->len;
                break;
        case 2:
                dcon |= S3C24XX_DCON_DSZ_HALFWORD | (dsg->len / 2);
                break;
        case 4:
                dcon |= S3C24XX_DCON_DSZ_WORD | (dsg->len / 4);
                break;
        }

        if (s3cchan->slave) {
                struct s3c24xx_dma_channel *cdata =
                                        &pdata->channels[s3cchan->id];

                if (s3cdma->sdata->has_reqsel) {
                        writel_relaxed((cdata->chansel << 1) |
                                                        S3C24XX_DMAREQSEL_HW,
                                        phy->base + S3C24XX_DMAREQSEL);
                } else {
                        int csel = cdata->chansel >> (phy->id *
                                                        S3C24XX_CHANSEL_WIDTH);

                        csel &= S3C24XX_CHANSEL_REQ_MASK;
                        dcon |= csel << S3C24XX_DCON_HWSRC_SHIFT;
                        dcon |= S3C24XX_DCON_HWTRIG;
                }
        } else {
                if (s3cdma->sdata->has_reqsel)
                        writel_relaxed(0, phy->base + S3C24XX_DMAREQSEL);
        }

        writel_relaxed(dsg->src_addr, phy->base + S3C24XX_DISRC);
        writel_relaxed(txd->disrcc, phy->base + S3C24XX_DISRCC);
        writel_relaxed(dsg->dst_addr, phy->base + S3C24XX_DIDST);
        writel_relaxed(txd->didstc, phy->base + S3C24XX_DIDSTC);
        writel_relaxed(dcon, phy->base + S3C24XX_DCON);

        val = readl_relaxed(phy->base + S3C24XX_DMASKTRIG);
        val &= ~S3C24XX_DMASKTRIG_STOP;
        val |= S3C24XX_DMASKTRIG_ON;

        /* trigger the dma operation for memcpy transfers */
        if (!s3cchan->slave)
                val |= S3C24XX_DMASKTRIG_SWTRIG;

        writel(val, phy->base + S3C24XX_DMASKTRIG);
}

/*
 * Set the initial DMA register values and start first sg.
 */
static void s3c24xx_dma_start_next_txd(struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_phy *phy = s3cchan->phy;
        struct virt_dma_desc *vd = vchan_next_desc(&s3cchan->vc);
        struct s3c24xx_txd *txd = to_s3c24xx_txd(&vd->tx);

        list_del(&txd->vd.node);

        s3cchan->at = txd;

        /* Wait for channel inactive */
        while (s3c24xx_dma_phy_busy(phy))
                cpu_relax();

        /* point to the first element of the sg list */
        txd->at = txd->dsg_list.next;
        s3c24xx_dma_start_next_sg(s3cchan, txd);
}

static void s3c24xx_dma_free_txd_list(struct s3c24xx_dma_engine *s3cdma,
                                struct s3c24xx_dma_chan *s3cchan)
{
        LIST_HEAD(head);

        vchan_get_all_descriptors(&s3cchan->vc, &head);
        vchan_dma_desc_free_list(&s3cchan->vc, &head);
}

/*
 * Try to allocate a physical channel.  When successful, assign it to
 * this virtual channel, and initiate the next descriptor.  The
 * virtual channel lock must be held at this point.
 */
static void s3c24xx_dma_phy_alloc_and_start(struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        struct s3c24xx_dma_phy *phy;

        phy = s3c24xx_dma_get_phy(s3cchan);
        if (!phy) {
                dev_dbg(&s3cdma->pdev->dev, "no physical channel available for xfer on %s\n",
                        s3cchan->name);
                s3cchan->state = S3C24XX_DMA_CHAN_WAITING;
                return;
        }

        dev_dbg(&s3cdma->pdev->dev, "allocated physical channel %d for xfer on %s\n",
                phy->id, s3cchan->name);

        s3cchan->phy = phy;
        s3cchan->state = S3C24XX_DMA_CHAN_RUNNING;

        s3c24xx_dma_start_next_txd(s3cchan);
}

static void s3c24xx_dma_phy_reassign_start(struct s3c24xx_dma_phy *phy,
        struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;

        dev_dbg(&s3cdma->pdev->dev, "reassigned physical channel %d for xfer on %s\n",
                phy->id, s3cchan->name);

        /*
         * We do this without taking the lock; we're really only concerned
         * about whether this pointer is NULL or not, and we're guaranteed
         * that this will only be called when it _already_ is non-NULL.
         */
        phy->serving = s3cchan;
        s3cchan->phy = phy;
        s3cchan->state = S3C24XX_DMA_CHAN_RUNNING;
        s3c24xx_dma_start_next_txd(s3cchan);
}

/*
 * Free a physical DMA channel, potentially reallocating it to another
 * virtual channel if we have any pending.
 */
static void s3c24xx_dma_phy_free(struct s3c24xx_dma_chan *s3cchan)
{
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        struct s3c24xx_dma_chan *p, *next;

retry:
        next = NULL;

        /* Find a waiting virtual channel for the next transfer. */
        list_for_each_entry(p, &s3cdma->memcpy.channels, vc.chan.device_node)
                if (p->state == S3C24XX_DMA_CHAN_WAITING) {
                        next = p;
                        break;
                }

        if (!next) {
                list_for_each_entry(p, &s3cdma->slave.channels,
                                    vc.chan.device_node)
                        if (p->state == S3C24XX_DMA_CHAN_WAITING &&
                                      s3c24xx_dma_phy_valid(p, s3cchan->phy)) {
                                next = p;
                                break;
                        }
        }

        /* Ensure that the physical channel is stopped */
        s3c24xx_dma_terminate_phy(s3cchan->phy);

        if (next) {
                bool success;

                /*
                 * Eww.  We know this isn't going to deadlock
                 * but lockdep probably doesn't.
                 */
                spin_lock(&next->vc.lock);
                /* Re-check the state now that we have the lock */
                success = next->state == S3C24XX_DMA_CHAN_WAITING;
                if (success)
                        s3c24xx_dma_phy_reassign_start(s3cchan->phy, next);
                spin_unlock(&next->vc.lock);

                /* If the state changed, try to find another channel */
                if (!success)
                        goto retry;
        } else {
                /* No more jobs, so free up the physical channel */
                s3c24xx_dma_put_phy(s3cchan->phy);
        }

        s3cchan->phy = NULL;
        s3cchan->state = S3C24XX_DMA_CHAN_IDLE;
}

static void s3c24xx_dma_unmap_buffers(struct s3c24xx_txd *txd)
{
        struct device *dev = txd->vd.tx.chan->device->dev;
        struct s3c24xx_sg *dsg;

        if (!(txd->vd.tx.flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
                if (txd->vd.tx.flags & DMA_COMPL_SRC_UNMAP_SINGLE)
                        list_for_each_entry(dsg, &txd->dsg_list, node)
                                dma_unmap_single(dev, dsg->src_addr, dsg->len,
                                                DMA_TO_DEVICE);
                else {
                        list_for_each_entry(dsg, &txd->dsg_list, node)
                                dma_unmap_page(dev, dsg->src_addr, dsg->len,
                                                DMA_TO_DEVICE);
                }
        }

        if (!(txd->vd.tx.flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
                if (txd->vd.tx.flags & DMA_COMPL_DEST_UNMAP_SINGLE)
                        list_for_each_entry(dsg, &txd->dsg_list, node)
                                dma_unmap_single(dev, dsg->dst_addr, dsg->len,
                                                DMA_FROM_DEVICE);
                else
                        list_for_each_entry(dsg, &txd->dsg_list, node)
                                dma_unmap_page(dev, dsg->dst_addr, dsg->len,
                                                DMA_FROM_DEVICE);
        }
}

static void s3c24xx_dma_desc_free(struct virt_dma_desc *vd)
{
        struct s3c24xx_txd *txd = to_s3c24xx_txd(&vd->tx);
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(vd->tx.chan);

        if (!s3cchan->slave)
                s3c24xx_dma_unmap_buffers(txd);

        s3c24xx_dma_free_txd(txd);
}

static irqreturn_t s3c24xx_dma_irq(int irq, void *data)
{
        struct s3c24xx_dma_phy *phy = data;
        struct s3c24xx_dma_chan *s3cchan = phy->serving;
        struct s3c24xx_txd *txd;

        dev_dbg(&phy->host->pdev->dev, "interrupt on channel %d\n", phy->id);

        /*
         * Interrupts happen to notify the completion of a transfer and the
         * channel should have moved into its stop state already on its own.
         * Therefore interrupts on channels not bound to a virtual channel
         * should never happen. Nevertheless send a terminate command to the
         * channel if the unlikely case happens.
         */
        if (unlikely(!s3cchan)) {
                dev_err(&phy->host->pdev->dev, "interrupt on unused channel %d\n",
                        phy->id);

                s3c24xx_dma_terminate_phy(phy);

                return IRQ_HANDLED;
        }

        spin_lock(&s3cchan->vc.lock);
        txd = s3cchan->at;
        if (txd) {
                /* when more sg's are in this txd, start the next one */
                if (!list_is_last(txd->at, &txd->dsg_list)) {
                        txd->at = txd->at->next;
                        s3c24xx_dma_start_next_sg(s3cchan, txd);
                } else {
                        s3cchan->at = NULL;
                        vchan_cookie_complete(&txd->vd);

                        /*
                         * And start the next descriptor (if any),
                         * otherwise free this channel.
                         */
                        if (vchan_next_desc(&s3cchan->vc))
                                s3c24xx_dma_start_next_txd(s3cchan);
                        else
                                s3c24xx_dma_phy_free(s3cchan);
                }
        }
        spin_unlock(&s3cchan->vc.lock);

        return IRQ_HANDLED;
}

/*
 * The DMA ENGINE API
 */

static int s3c24xx_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
                         unsigned long arg)
{
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(chan);
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&s3cchan->vc.lock, flags);

        switch (cmd) {
        case DMA_SLAVE_CONFIG:
                ret = s3c24xx_dma_set_runtime_config(s3cchan,
                                              (struct dma_slave_config *)arg);
                break;
        case DMA_TERMINATE_ALL:
                if (!s3cchan->phy && !s3cchan->at) {
                        dev_err(&s3cdma->pdev->dev, "trying to terminate already stopped channel %d\n",
                                s3cchan->id);
                        ret = -EINVAL;
                        break;
                }

                s3cchan->state = S3C24XX_DMA_CHAN_IDLE;

                 /* Mark physical channel as free */
                if (s3cchan->phy)
                        s3c24xx_dma_phy_free(s3cchan);

                /* Dequeue current job */
                if (s3cchan->at) {
                        s3c24xx_dma_desc_free(&s3cchan->at->vd);
                        s3cchan->at = NULL;
                }

                /* Dequeue jobs not yet fired as well */
                s3c24xx_dma_free_txd_list(s3cdma, s3cchan);
                break;
        default:
                /* Unknown command */
                ret = -ENXIO;
                break;
        }

        spin_unlock_irqrestore(&s3cchan->vc.lock, flags);

        return ret;
}

static int s3c24xx_dma_alloc_chan_resources(struct dma_chan *chan)
{
        return 0;
}

static void s3c24xx_dma_free_chan_resources(struct dma_chan *chan)
{
        /* Ensure all queued descriptors are freed */
        vchan_free_chan_resources(to_virt_chan(chan));
}

static enum dma_status s3c24xx_dma_tx_status(struct dma_chan *chan,
                dma_cookie_t cookie, struct dma_tx_state *txstate)
{
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(chan);
        struct s3c24xx_txd *txd;
        struct s3c24xx_sg *dsg;
        struct virt_dma_desc *vd;
        unsigned long flags;
        enum dma_status ret;
        size_t bytes = 0;

        spin_lock_irqsave(&s3cchan->vc.lock, flags);
        ret = dma_cookie_status(chan, cookie, txstate);
        if (ret == DMA_SUCCESS) {
                spin_unlock_irqrestore(&s3cchan->vc.lock, flags);
                return ret;
        }

        /*
         * There's no point calculating the residue if there's
         * no txstate to store the value.
         */
        if (!txstate) {
                spin_unlock_irqrestore(&s3cchan->vc.lock, flags);
                return ret;
        }

        vd = vchan_find_desc(&s3cchan->vc, cookie);
        if (vd) {
                /* On the issued list, so hasn't been processed yet */
                txd = to_s3c24xx_txd(&vd->tx);

                list_for_each_entry(dsg, &txd->dsg_list, node)
                        bytes += dsg->len;
        } else {
                /*
                 * Currently running, so sum over the pending sg's and
                 * the currently active one.
                 */
                txd = s3cchan->at;

                dsg = list_entry(txd->at, struct s3c24xx_sg, node);
                list_for_each_entry_from(dsg, &txd->dsg_list, node)
                        bytes += dsg->len;

                bytes += s3c24xx_dma_getbytes_chan(s3cchan);
        }
        spin_unlock_irqrestore(&s3cchan->vc.lock, flags);

        /*
         * This cookie not complete yet
         * Get number of bytes left in the active transactions and queue
         */
        dma_set_residue(txstate, bytes);

        /* Whether waiting or running, we're in progress */
        return ret;
}

/*
 * Initialize a descriptor to be used by memcpy submit
 */
static struct dma_async_tx_descriptor *s3c24xx_dma_prep_memcpy(
                struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
                size_t len, unsigned long flags)
{
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(chan);
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        struct s3c24xx_txd *txd;
        struct s3c24xx_sg *dsg;
        int src_mod, dest_mod;

        dev_dbg(&s3cdma->pdev->dev, "prepare memcpy of %d bytes from %s\n",
                        len, s3cchan->name);

        if ((len & S3C24XX_DCON_TC_MASK) != len) {
                dev_err(&s3cdma->pdev->dev, "memcpy size %d to large\n", len);
                return NULL;
        }

        txd = s3c24xx_dma_get_txd();
        if (!txd)
                return NULL;

        dsg = kzalloc(sizeof(*dsg), GFP_NOWAIT);
        if (!dsg) {
                s3c24xx_dma_free_txd(txd);
                return NULL;
        }
        list_add_tail(&dsg->node, &txd->dsg_list);

        dsg->src_addr = src;
        dsg->dst_addr = dest;
        dsg->len = len;

        /*
         * Determine a suitable transfer width.
         * The DMA controller cannot fetch/store information which is not
         * naturally aligned on the bus, i.e., a 4 byte fetch must start at
         * an address divisible by 4 - more generally addr % width must be 0.
         */
        src_mod = src % 4;
        dest_mod = dest % 4;
        switch (len % 4) {
        case 0:
                txd->width = (src_mod == 0 && dest_mod == 0) ? 4 : 1;
                break;
        case 2:
                txd->width = ((src_mod == 2 || src_mod == 0) &&
                              (dest_mod == 2 || dest_mod == 0)) ? 2 : 1;
                break;
        default:
                txd->width = 1;
                break;
        }

        txd->disrcc = S3C24XX_DISRCC_LOC_AHB | S3C24XX_DISRCC_INC_INCREMENT;
        txd->didstc = S3C24XX_DIDSTC_LOC_AHB | S3C24XX_DIDSTC_INC_INCREMENT;
        txd->dcon |= S3C24XX_DCON_DEMAND | S3C24XX_DCON_SYNC_HCLK |
                     S3C24XX_DCON_SERV_WHOLE;

        return vchan_tx_prep(&s3cchan->vc, &txd->vd, flags);
}

static struct dma_async_tx_descriptor *s3c24xx_dma_prep_slave_sg(
                struct dma_chan *chan, struct scatterlist *sgl,
                unsigned int sg_len, enum dma_transfer_direction direction,
                unsigned long flags, void *context)
{
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(chan);
        struct s3c24xx_dma_engine *s3cdma = s3cchan->host;
        const struct s3c24xx_dma_platdata *pdata = s3cdma->pdata;
        struct s3c24xx_dma_channel *cdata = &pdata->channels[s3cchan->id];
        struct s3c24xx_txd *txd;
        struct s3c24xx_sg *dsg;
        struct scatterlist *sg;
        dma_addr_t slave_addr;
        u32 hwcfg = 0;
        int tmp;

        dev_dbg(&s3cdma->pdev->dev, "prepare transaction of %d bytes from %s\n",
                        sg_dma_len(sgl), s3cchan->name);

        txd = s3c24xx_dma_get_txd();
        if (!txd)
                return NULL;

        if (cdata->handshake)
                txd->dcon |= S3C24XX_DCON_HANDSHAKE;

        switch (cdata->bus) {
        case S3C24XX_DMA_APB:
                txd->dcon |= S3C24XX_DCON_SYNC_PCLK;
                hwcfg |= S3C24XX_DISRCC_LOC_APB;
                break;
        case S3C24XX_DMA_AHB:
                txd->dcon |= S3C24XX_DCON_SYNC_HCLK;
                hwcfg |= S3C24XX_DISRCC_LOC_AHB;
                break;
        }

        /*
         * Always assume our peripheral desintation is a fixed
         * address in memory.
         */
        hwcfg |= S3C24XX_DISRCC_INC_FIXED;

        /*
         * Individual dma operations are requested by the slave,
         * so serve only single atomic operations (S3C24XX_DCON_SERV_SINGLE).
         */
        txd->dcon |= S3C24XX_DCON_SERV_SINGLE;

        if (direction == DMA_MEM_TO_DEV) {
                txd->disrcc = S3C24XX_DISRCC_LOC_AHB |
                              S3C24XX_DISRCC_INC_INCREMENT;
                txd->didstc = hwcfg;
                slave_addr = s3cchan->cfg.dst_addr;
                txd->width = s3cchan->cfg.dst_addr_width;
        } else if (direction == DMA_DEV_TO_MEM) {
                txd->disrcc = hwcfg;
                txd->didstc = S3C24XX_DIDSTC_LOC_AHB |
                              S3C24XX_DIDSTC_INC_INCREMENT;
                slave_addr = s3cchan->cfg.src_addr;
                txd->width = s3cchan->cfg.src_addr_width;
        } else {
                s3c24xx_dma_free_txd(txd);
                dev_err(&s3cdma->pdev->dev,
                        "direction %d unsupported\n", direction);
                return NULL;
        }

        for_each_sg(sgl, sg, sg_len, tmp) {
                dsg = kzalloc(sizeof(*dsg), GFP_NOWAIT);
                if (!dsg) {
                        s3c24xx_dma_free_txd(txd);
                        return NULL;
                }
                list_add_tail(&dsg->node, &txd->dsg_list);

                dsg->len = sg_dma_len(sg);
                if (direction == DMA_MEM_TO_DEV) {
                        dsg->src_addr = sg_dma_address(sg);
                        dsg->dst_addr = slave_addr;
                } else { /* DMA_DEV_TO_MEM */
                        dsg->src_addr = slave_addr;
                        dsg->dst_addr = sg_dma_address(sg);
                }
                break;
        }

        return vchan_tx_prep(&s3cchan->vc, &txd->vd, flags);
}

/*
 * Slave transactions callback to the slave device to allow
 * synchronization of slave DMA signals with the DMAC enable
 */
static void s3c24xx_dma_issue_pending(struct dma_chan *chan)
{
        struct s3c24xx_dma_chan *s3cchan = to_s3c24xx_dma_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&s3cchan->vc.lock, flags);
        if (vchan_issue_pending(&s3cchan->vc)) {
                if (!s3cchan->phy && s3cchan->state != S3C24XX_DMA_CHAN_WAITING)
                        s3c24xx_dma_phy_alloc_and_start(s3cchan);
        }
        spin_unlock_irqrestore(&s3cchan->vc.lock, flags);
}

/*
 * Bringup and teardown
 */

/*
 * Initialise the DMAC memcpy/slave channels.
 * Make a local wrapper to hold required data
 */
static int s3c24xx_dma_init_virtual_channels(struct s3c24xx_dma_engine *s3cdma,
                struct dma_device *dmadev, unsigned int channels, bool slave)
{
        struct s3c24xx_dma_chan *chan;
        int i;

        INIT_LIST_HEAD(&dmadev->channels);

        /*
         * Register as many many memcpy as we have physical channels,
         * we won't always be able to use all but the code will have
         * to cope with that situation.
         */
        for (i = 0; i < channels; i++) {
                chan = devm_kzalloc(dmadev->dev, sizeof(*chan), GFP_KERNEL);
                if (!chan) {
                        dev_err(dmadev->dev,
                                "%s no memory for channel\n", __func__);
                        return -ENOMEM;
                }

                chan->id = i;
                chan->host = s3cdma;
                chan->state = S3C24XX_DMA_CHAN_IDLE;

                if (slave) {
                        chan->slave = true;
                        chan->name = kasprintf(GFP_KERNEL, "slave%d", i);
                        if (!chan->name)
                                return -ENOMEM;
                } else {
                        chan->name = kasprintf(GFP_KERNEL, "memcpy%d", i);
                        if (!chan->name)
                                return -ENOMEM;
                }
                dev_dbg(dmadev->dev,
                         "initialize virtual channel \"%s\"\n",
                         chan->name);

                chan->vc.desc_free = s3c24xx_dma_desc_free;
                vchan_init(&chan->vc, dmadev);
        }
        dev_info(dmadev->dev, "initialized %d virtual %s channels\n",
                 i, slave ? "slave" : "memcpy");
        return i;
}

static void s3c24xx_dma_free_virtual_channels(struct dma_device *dmadev)
{
        struct s3c24xx_dma_chan *chan = NULL;
        struct s3c24xx_dma_chan *next;

        list_for_each_entry_safe(chan,
                                 next, &dmadev->channels, vc.chan.device_node)
                list_del(&chan->vc.chan.device_node);
}

/* s3c2410, s3c2440 and s3c2442 have a 0x40 stride without separate clocks */
static struct soc_data soc_s3c2410 = {
        .stride = 0x40,
        .has_reqsel = false,
        .has_clocks = false,
};

/* s3c2412 and s3c2413 have a 0x40 stride and dmareqsel mechanism */
static struct soc_data soc_s3c2412 = {
        .stride = 0x40,
        .has_reqsel = true,
        .has_clocks = true,
};

/* s3c2443 and following have a 0x100 stride and dmareqsel mechanism */
static struct soc_data soc_s3c2443 = {
        .stride = 0x100,
        .has_reqsel = true,
        .has_clocks = true,
};

static struct platform_device_id s3c24xx_dma_driver_ids[] = {
        {
                .name           = "s3c2410-dma",
                .driver_data    = (kernel_ulong_t)&soc_s3c2410,
        }, {
                .name           = "s3c2412-dma",
                .driver_data    = (kernel_ulong_t)&soc_s3c2412,
        }, {
                .name           = "s3c2443-dma",
                .driver_data    = (kernel_ulong_t)&soc_s3c2443,
        },
        { },
};

static struct soc_data *s3c24xx_dma_get_soc_data(struct platform_device *pdev)
{
        return (struct soc_data *)
                         platform_get_device_id(pdev)->driver_data;
}

static int s3c24xx_dma_probe(struct platform_device *pdev)
{
        const struct s3c24xx_dma_platdata *pdata = dev_get_platdata(&pdev->dev);
        struct s3c24xx_dma_engine *s3cdma;
        struct soc_data *sdata;
        struct resource *res;
        int ret;
        int i;

        if (!pdata) {
                dev_err(&pdev->dev, "platform data missing\n");
                return -ENODEV;
        }

        /* Basic sanity check */
        if (pdata->num_phy_channels > MAX_DMA_CHANNELS) {
                dev_err(&pdev->dev, "to many dma channels %d, max %d\n",
                        pdata->num_phy_channels, MAX_DMA_CHANNELS);
                return -EINVAL;
        }

        sdata = s3c24xx_dma_get_soc_data(pdev);
        if (!sdata)
                return -EINVAL;

        s3cdma = devm_kzalloc(&pdev->dev, sizeof(*s3cdma), GFP_KERNEL);
        if (!s3cdma)
                return -ENOMEM;

        s3cdma->pdev = pdev;
        s3cdma->pdata = pdata;
        s3cdma->sdata = sdata;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        s3cdma->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(s3cdma->base))
                return PTR_ERR(s3cdma->base);

        s3cdma->phy_chans = devm_kzalloc(&pdev->dev,
                                              sizeof(struct s3c24xx_dma_phy) *
                                                        pdata->num_phy_channels,
                                              GFP_KERNEL);
        if (!s3cdma->phy_chans)
                return -ENOMEM;

        /* aquire irqs and clocks for all physical channels */
        for (i = 0; i < pdata->num_phy_channels; i++) {
                struct s3c24xx_dma_phy *phy = &s3cdma->phy_chans[i];
                char clk_name[6];

                phy->id = i;
                phy->base = s3cdma->base + (i * sdata->stride);
                phy->host = s3cdma;

                phy->irq = platform_get_irq(pdev, i);
                if (phy->irq < 0) {
                        dev_err(&pdev->dev, "failed to get irq %d, err %d\n",
                                i, phy->irq);
                        continue;
                }

                ret = devm_request_irq(&pdev->dev, phy->irq, s3c24xx_dma_irq,
                                       0, pdev->name, phy);
                if (ret) {
                        dev_err(&pdev->dev, "Unable to request irq for channel %d, error %d\n",
                                i, ret);
                        continue;
                }

                if (sdata->has_clocks) {
                        sprintf(clk_name, "dma.%d", i);
                        phy->clk = devm_clk_get(&pdev->dev, clk_name);
                        if (IS_ERR(phy->clk) && sdata->has_clocks) {
                                dev_err(&pdev->dev, "unable to aquire clock for channel %d, error %lu",
                                        i, PTR_ERR(phy->clk));
                                continue;
                        }

                        ret = clk_prepare(phy->clk);
                        if (ret) {
                                dev_err(&pdev->dev, "clock for phy %d failed, error %d\n",
                                        i, ret);
                                continue;
                        }
                }

                spin_lock_init(&phy->lock);
                phy->valid = true;

                dev_dbg(&pdev->dev, "physical channel %d is %s\n",
                        i, s3c24xx_dma_phy_busy(phy) ? "BUSY" : "FREE");
        }

        /* Initialize memcpy engine */
        dma_cap_set(DMA_MEMCPY, s3cdma->memcpy.cap_mask);
        dma_cap_set(DMA_PRIVATE, s3cdma->memcpy.cap_mask);
        s3cdma->memcpy.dev = &pdev->dev;
        s3cdma->memcpy.device_alloc_chan_resources =
                                        s3c24xx_dma_alloc_chan_resources;
        s3cdma->memcpy.device_free_chan_resources =
                                        s3c24xx_dma_free_chan_resources;
        s3cdma->memcpy.device_prep_dma_memcpy = s3c24xx_dma_prep_memcpy;
        s3cdma->memcpy.device_tx_status = s3c24xx_dma_tx_status;
        s3cdma->memcpy.device_issue_pending = s3c24xx_dma_issue_pending;
        s3cdma->memcpy.device_control = s3c24xx_dma_control;

        /* Initialize slave engine for SoC internal dedicated peripherals */
        dma_cap_set(DMA_SLAVE, s3cdma->slave.cap_mask);
        dma_cap_set(DMA_PRIVATE, s3cdma->slave.cap_mask);
        s3cdma->slave.dev = &pdev->dev;
        s3cdma->slave.device_alloc_chan_resources =
                                        s3c24xx_dma_alloc_chan_resources;
        s3cdma->slave.device_free_chan_resources =
                                        s3c24xx_dma_free_chan_resources;
        s3cdma->slave.device_tx_status = s3c24xx_dma_tx_status;
        s3cdma->slave.device_issue_pending = s3c24xx_dma_issue_pending;
        s3cdma->slave.device_prep_slave_sg = s3c24xx_dma_prep_slave_sg;
        s3cdma->slave.device_control = s3c24xx_dma_control;

        /* Register as many memcpy channels as there are physical channels */
        ret = s3c24xx_dma_init_virtual_channels(s3cdma, &s3cdma->memcpy,
                                                pdata->num_phy_channels, false);
        if (ret <= 0) {
                dev_warn(&pdev->dev,
                         "%s failed to enumerate memcpy channels - %d\n",
                         __func__, ret);
                goto err_memcpy;
        }

        /* Register slave channels */
        ret = s3c24xx_dma_init_virtual_channels(s3cdma, &s3cdma->slave,
                                pdata->num_channels, true);
        if (ret <= 0) {
                dev_warn(&pdev->dev,
                        "%s failed to enumerate slave channels - %d\n",
                                __func__, ret);
                goto err_slave;
        }

        ret = dma_async_device_register(&s3cdma->memcpy);
        if (ret) {
                dev_warn(&pdev->dev,
                        "%s failed to register memcpy as an async device - %d\n",
                        __func__, ret);
                goto err_memcpy_reg;
        }

        ret = dma_async_device_register(&s3cdma->slave);
        if (ret) {
                dev_warn(&pdev->dev,
                        "%s failed to register slave as an async device - %d\n",
                        __func__, ret);
                goto err_slave_reg;
        }

        platform_set_drvdata(pdev, s3cdma);
        dev_info(&pdev->dev, "Loaded dma driver with %d physical channels\n",
                 pdata->num_phy_channels);

        return 0;

err_slave_reg:
        dma_async_device_unregister(&s3cdma->memcpy);
err_memcpy_reg:
        s3c24xx_dma_free_virtual_channels(&s3cdma->slave);
err_slave:
        s3c24xx_dma_free_virtual_channels(&s3cdma->memcpy);
err_memcpy:
        if (sdata->has_clocks)
                for (i = 0; i < pdata->num_phy_channels; i++) {
                        struct s3c24xx_dma_phy *phy = &s3cdma->phy_chans[i];
                        if (phy->valid)
                                clk_unprepare(phy->clk);
                }

        return ret;
}

static int s3c24xx_dma_remove(struct platform_device *pdev)
{
        const struct s3c24xx_dma_platdata *pdata = dev_get_platdata(&pdev->dev);
        struct s3c24xx_dma_engine *s3cdma = platform_get_drvdata(pdev);
        struct soc_data *sdata = s3c24xx_dma_get_soc_data(pdev);
        int i;

        dma_async_device_unregister(&s3cdma->slave);
        dma_async_device_unregister(&s3cdma->memcpy);

        s3c24xx_dma_free_virtual_channels(&s3cdma->slave);
        s3c24xx_dma_free_virtual_channels(&s3cdma->memcpy);

        if (sdata->has_clocks)
                for (i = 0; i < pdata->num_phy_channels; i++) {
                        struct s3c24xx_dma_phy *phy = &s3cdma->phy_chans[i];
                        if (phy->valid)
                                clk_unprepare(phy->clk);
                }

        return 0;
}

static struct platform_driver s3c24xx_dma_driver = {
        .driver         = {
                .name   = "s3c24xx-dma",
                .owner  = THIS_MODULE,
        },
        .id_table       = s3c24xx_dma_driver_ids,
        .probe          = s3c24xx_dma_probe,
        .remove         = s3c24xx_dma_remove,
};

module_platform_driver(s3c24xx_dma_driver);

bool s3c24xx_dma_filter(struct dma_chan *chan, void *param)
{
        struct s3c24xx_dma_chan *s3cchan;

        if (chan->device->dev->driver != &s3c24xx_dma_driver.driver)
                return false;

        s3cchan = to_s3c24xx_dma_chan(chan);

        return s3cchan->id == (int)param;
}
EXPORT_SYMBOL(s3c24xx_dma_filter);

MODULE_DESCRIPTION("S3C24XX DMA Driver");
MODULE_AUTHOR("Heiko Stuebner");
MODULE_LICENSE("GPL v2");