// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) Freescale Semicondutor, Inc. 2007, 2008.
 * Copyright (C) Semihalf 2009
 * Copyright (C) Ilya Yanok, Emcraft Systems 2010
 * Copyright (C) Alexander Popov, Promcontroller 2014
 * Copyright (C) Mario Six, Guntermann & Drunck GmbH, 2016
 *
 * Written by Piotr Ziecik <kosmo@semihalf.com>. Hardware description
 * (defines, structures and comments) was taken from MPC5121 DMA driver
 * written by Hongjun Chen <hong-jun.chen@freescale.com>.
 *
 * Approved as OSADL project by a majority of OSADL members and funded
 * by OSADL membership fees in 2009;  for details see www.osadl.org.
 */

/*
 * MPC512x and MPC8308 DMA driver. It supports memory to memory data transfers
 * (tested using dmatest module) and data transfers between memory and
 * peripheral I/O memory by means of slave scatter/gather with these
 * limitations:
 *  - chunked transfers (described by s/g lists with more than one item) are
 *     refused as long as proper support for scatter/gather is missing
 *  - transfers on MPC8308 always start from software as this SoC does not have
 *     external request lines for peripheral flow control
 *  - memory <-> I/O memory transfer chunks of sizes of 1, 2, 4, 16 (for
 *     MPC512x), and 32 bytes are supported, and, consequently, source
 *     addresses and destination addresses must be aligned accordingly;
 *     furthermore, for MPC512x SoCs, the transfer size must be aligned on
 *     (chunk size * maxburst)
 */

#include <linux/module.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_irq.h>
#include <linux/of_dma.h>
#include <linux/of_platform.h>

#include <linux/random.h>

#include "dmaengine.h"

/* Number of DMA Transfer descriptors allocated per channel */
#define MPC_DMA_DESCRIPTORS     64

/* Macro definitions */
#define MPC_DMA_TCD_OFFSET      0x1000

/*
 * Maximum channel counts for individual hardware variants
 * and the maximum channel count over all supported controllers,
 * used for data structure size
 */
#define MPC8308_DMACHAN_MAX     16
#define MPC512x_DMACHAN_MAX     64
#define MPC_DMA_CHANNELS        64

/* Arbitration mode of group and channel */
#define MPC_DMA_DMACR_EDCG      (1 << 31)
#define MPC_DMA_DMACR_ERGA      (1 << 3)
#define MPC_DMA_DMACR_ERCA      (1 << 2)

/* Error codes */
#define MPC_DMA_DMAES_VLD       (1 << 31)
#define MPC_DMA_DMAES_GPE       (1 << 15)
#define MPC_DMA_DMAES_CPE       (1 << 14)
#define MPC_DMA_DMAES_ERRCHN(err) \
                                (((err) >> 8) & 0x3f)
#define MPC_DMA_DMAES_SAE       (1 << 7)
#define MPC_DMA_DMAES_SOE       (1 << 6)
#define MPC_DMA_DMAES_DAE       (1 << 5)
#define MPC_DMA_DMAES_DOE       (1 << 4)
#define MPC_DMA_DMAES_NCE       (1 << 3)
#define MPC_DMA_DMAES_SGE       (1 << 2)
#define MPC_DMA_DMAES_SBE       (1 << 1)
#define MPC_DMA_DMAES_DBE       (1 << 0)

#define MPC_DMA_DMAGPOR_SNOOP_ENABLE    (1 << 6)

#define MPC_DMA_TSIZE_1         0x00
#define MPC_DMA_TSIZE_2         0x01
#define MPC_DMA_TSIZE_4         0x02
#define MPC_DMA_TSIZE_16        0x04
#define MPC_DMA_TSIZE_32        0x05

/* MPC5121 DMA engine registers */
struct __attribute__ ((__packed__)) mpc_dma_regs {
        /* 0x00 */
        u32 dmacr;              /* DMA control register */
        u32 dmaes;              /* DMA error status */
        /* 0x08 */
        u32 dmaerqh;            /* DMA enable request high(channels 63~32) */
        u32 dmaerql;            /* DMA enable request low(channels 31~0) */
        u32 dmaeeih;            /* DMA enable error interrupt high(ch63~32) */
        u32 dmaeeil;            /* DMA enable error interrupt low(ch31~0) */
        /* 0x18 */
        u8 dmaserq;             /* DMA set enable request */
        u8 dmacerq;             /* DMA clear enable request */
        u8 dmaseei;             /* DMA set enable error interrupt */
        u8 dmaceei;             /* DMA clear enable error interrupt */
        /* 0x1c */
        u8 dmacint;             /* DMA clear interrupt request */
        u8 dmacerr;             /* DMA clear error */
        u8 dmassrt;             /* DMA set start bit */
        u8 dmacdne;             /* DMA clear DONE status bit */
        /* 0x20 */
        u32 dmainth;            /* DMA interrupt request high(ch63~32) */
        u32 dmaintl;            /* DMA interrupt request low(ch31~0) */
        u32 dmaerrh;            /* DMA error high(ch63~32) */
        u32 dmaerrl;            /* DMA error low(ch31~0) */
        /* 0x30 */
        u32 dmahrsh;            /* DMA hw request status high(ch63~32) */
        u32 dmahrsl;            /* DMA hardware request status low(ch31~0) */
        union {
                u32 dmaihsa;    /* DMA interrupt high select AXE(ch63~32) */
                u32 dmagpor;    /* (General purpose register on MPC8308) */
        };
        u32 dmailsa;            /* DMA interrupt low select AXE(ch31~0) */
        /* 0x40 ~ 0xff */
        u32 reserve0[48];       /* Reserved */
        /* 0x100 */
        u8 dchpri[MPC_DMA_CHANNELS];
        /* DMA channels(0~63) priority */
};

struct __attribute__ ((__packed__)) mpc_dma_tcd {
        /* 0x00 */
        u32 saddr;              /* Source address */

        u32 smod:5;             /* Source address modulo */
        u32 ssize:3;            /* Source data transfer size */
        u32 dmod:5;             /* Destination address modulo */
        u32 dsize:3;            /* Destination data transfer size */
        u32 soff:16;            /* Signed source address offset */

        /* 0x08 */
        u32 nbytes;             /* Inner "minor" byte count */
        u32 slast;              /* Last source address adjustment */
        u32 daddr;              /* Destination address */

        /* 0x14 */
        u32 citer_elink:1;      /* Enable channel-to-channel linking on
                                 * minor loop complete
                                 */
        u32 citer_linkch:6;     /* Link channel for minor loop complete */
        u32 citer:9;            /* Current "major" iteration count */
        u32 doff:16;            /* Signed destination address offset */

        /* 0x18 */
        u32 dlast_sga;          /* Last Destination address adjustment/scatter
                                 * gather address
                                 */

        /* 0x1c */
        u32 biter_elink:1;      /* Enable channel-to-channel linking on major
                                 * loop complete
                                 */
        u32 biter_linkch:6;
        u32 biter:9;            /* Beginning "major" iteration count */
        u32 bwc:2;              /* Bandwidth control */
        u32 major_linkch:6;     /* Link channel number */
        u32 done:1;             /* Channel done */
        u32 active:1;           /* Channel active */
        u32 major_elink:1;      /* Enable channel-to-channel linking on major
                                 * loop complete
                                 */
        u32 e_sg:1;             /* Enable scatter/gather processing */
        u32 d_req:1;            /* Disable request */
        u32 int_half:1;         /* Enable an interrupt when major counter is
                                 * half complete
                                 */
        u32 int_maj:1;          /* Enable an interrupt when major iteration
                                 * count completes
                                 */
        u32 start:1;            /* Channel start */
};

struct mpc_dma_desc {
        struct dma_async_tx_descriptor  desc;
        struct mpc_dma_tcd              *tcd;
        dma_addr_t                      tcd_paddr;
        int                             error;
        struct list_head                node;
        int                             will_access_peripheral;
};

struct mpc_dma_chan {
        struct dma_chan                 chan;
        struct list_head                free;
        struct list_head                prepared;
        struct list_head                queued;
        struct list_head                active;
        struct list_head                completed;
        struct mpc_dma_tcd              *tcd;
        dma_addr_t                      tcd_paddr;

        /* Settings for access to peripheral FIFO */
        dma_addr_t                      src_per_paddr;
        u32                             src_tcd_nunits;
        u8                              swidth;
        dma_addr_t                      dst_per_paddr;
        u32                             dst_tcd_nunits;
        u8                              dwidth;

        /* Lock for this structure */
        spinlock_t                      lock;
};

struct mpc_dma {
        struct dma_device               dma;
        struct tasklet_struct           tasklet;
        struct mpc_dma_chan             channels[MPC_DMA_CHANNELS];
        struct mpc_dma_regs __iomem     *regs;
        struct mpc_dma_tcd __iomem      *tcd;
        int                             irq;
        int                             irq2;
        uint                            error_status;
        int                             is_mpc8308;

        /* Lock for error_status field in this structure */
        spinlock_t                      error_status_lock;
};

#define DRV_NAME        "mpc512x_dma"

/* Convert struct dma_chan to struct mpc_dma_chan */
static inline struct mpc_dma_chan *dma_chan_to_mpc_dma_chan(struct dma_chan *c)
{
        return container_of(c, struct mpc_dma_chan, chan);
}

/* Convert struct dma_chan to struct mpc_dma */
static inline struct mpc_dma *dma_chan_to_mpc_dma(struct dma_chan *c)
{
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(c);

        return container_of(mchan, struct mpc_dma, channels[c->chan_id]);
}

/*
 * Execute all queued DMA descriptors.
 *
 * Following requirements must be met while calling mpc_dma_execute():
 *      a) mchan->lock is acquired,
 *      b) mchan->active list is empty,
 *      c) mchan->queued list contains at least one entry.
 */
static void mpc_dma_execute(struct mpc_dma_chan *mchan)
{
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(&mchan->chan);
        struct mpc_dma_desc *first = NULL;
        struct mpc_dma_desc *prev = NULL;
        struct mpc_dma_desc *mdesc;
        int cid = mchan->chan.chan_id;

        while (!list_empty(&mchan->queued)) {
                mdesc = list_first_entry(&mchan->queued,
                                                struct mpc_dma_desc, node);
                /*
                 * Grab either several mem-to-mem transfer descriptors
                 * or one peripheral transfer descriptor,
                 * don't mix mem-to-mem and peripheral transfer descriptors
                 * within the same 'active' list.
                 */
                if (mdesc->will_access_peripheral) {
                        if (list_empty(&mchan->active))
                                list_move_tail(&mdesc->node, &mchan->active);
                        break;
                } else {
                        list_move_tail(&mdesc->node, &mchan->active);
                }
        }

        /* Chain descriptors into one transaction */
        list_for_each_entry(mdesc, &mchan->active, node) {
                if (!first)
                        first = mdesc;

                if (!prev) {
                        prev = mdesc;
                        continue;
                }

                prev->tcd->dlast_sga = mdesc->tcd_paddr;
                prev->tcd->e_sg = 1;
                mdesc->tcd->start = 1;

                prev = mdesc;
        }

        prev->tcd->int_maj = 1;

        /* Send first descriptor in chain into hardware */
        memcpy_toio(&mdma->tcd[cid], first->tcd, sizeof(struct mpc_dma_tcd));

        if (first != prev)
                mdma->tcd[cid].e_sg = 1;

        if (mdma->is_mpc8308) {
                /* MPC8308, no request lines, software initiated start */
                out_8(&mdma->regs->dmassrt, cid);
        } else if (first->will_access_peripheral) {
                /* Peripherals involved, start by external request signal */
                out_8(&mdma->regs->dmaserq, cid);
        } else {
                /* Memory to memory transfer, software initiated start */
                out_8(&mdma->regs->dmassrt, cid);
        }
}

/* Handle interrupt on one half of DMA controller (32 channels) */
static void mpc_dma_irq_process(struct mpc_dma *mdma, u32 is, u32 es, int off)
{
        struct mpc_dma_chan *mchan;
        struct mpc_dma_desc *mdesc;
        u32 status = is | es;
        int ch;

        while ((ch = fls(status) - 1) >= 0) {
                status &= ~(1 << ch);
                mchan = &mdma->channels[ch + off];

                spin_lock(&mchan->lock);

                out_8(&mdma->regs->dmacint, ch + off);
                out_8(&mdma->regs->dmacerr, ch + off);

                /* Check error status */
                if (es & (1 << ch))
                        list_for_each_entry(mdesc, &mchan->active, node)
                                mdesc->error = -EIO;

                /* Execute queued descriptors */
                list_splice_tail_init(&mchan->active, &mchan->completed);
                if (!list_empty(&mchan->queued))
                        mpc_dma_execute(mchan);

                spin_unlock(&mchan->lock);
        }
}

/* Interrupt handler */
static irqreturn_t mpc_dma_irq(int irq, void *data)
{
        struct mpc_dma *mdma = data;
        uint es;

        /* Save error status register */
        es = in_be32(&mdma->regs->dmaes);
        spin_lock(&mdma->error_status_lock);
        if ((es & MPC_DMA_DMAES_VLD) && mdma->error_status == 0)
                mdma->error_status = es;
        spin_unlock(&mdma->error_status_lock);

        /* Handle interrupt on each channel */
        if (mdma->dma.chancnt > 32) {
                mpc_dma_irq_process(mdma, in_be32(&mdma->regs->dmainth),
                                        in_be32(&mdma->regs->dmaerrh), 32);
        }
        mpc_dma_irq_process(mdma, in_be32(&mdma->regs->dmaintl),
                                        in_be32(&mdma->regs->dmaerrl), 0);

        /* Schedule tasklet */
        tasklet_schedule(&mdma->tasklet);

        return IRQ_HANDLED;
}

/* process completed descriptors */
static void mpc_dma_process_completed(struct mpc_dma *mdma)
{
        dma_cookie_t last_cookie = 0;
        struct mpc_dma_chan *mchan;
        struct mpc_dma_desc *mdesc;
        struct dma_async_tx_descriptor *desc;
        unsigned long flags;
        LIST_HEAD(list);
        int i;

        for (i = 0; i < mdma->dma.chancnt; i++) {
                mchan = &mdma->channels[i];

                /* Get all completed descriptors */
                spin_lock_irqsave(&mchan->lock, flags);
                if (!list_empty(&mchan->completed))
                        list_splice_tail_init(&mchan->completed, &list);
                spin_unlock_irqrestore(&mchan->lock, flags);

                if (list_empty(&list))
                        continue;

                /* Execute callbacks and run dependencies */
                list_for_each_entry(mdesc, &list, node) {
                        desc = &mdesc->desc;

                        dmaengine_desc_get_callback_invoke(desc, NULL);

                        last_cookie = desc->cookie;
                        dma_run_dependencies(desc);
                }

                /* Free descriptors */
                spin_lock_irqsave(&mchan->lock, flags);
                list_splice_tail_init(&list, &mchan->free);
                mchan->chan.completed_cookie = last_cookie;
                spin_unlock_irqrestore(&mchan->lock, flags);
        }
}

/* DMA Tasklet */
static void mpc_dma_tasklet(struct tasklet_struct *t)
{
        struct mpc_dma *mdma = from_tasklet(mdma, t, tasklet);
        unsigned long flags;
        uint es;

        spin_lock_irqsave(&mdma->error_status_lock, flags);
        es = mdma->error_status;
        mdma->error_status = 0;
        spin_unlock_irqrestore(&mdma->error_status_lock, flags);

        /* Print nice error report */
        if (es) {
                dev_err(mdma->dma.dev,
                        "Hardware reported following error(s) on channel %u:\n",
                                                      MPC_DMA_DMAES_ERRCHN(es));

                if (es & MPC_DMA_DMAES_GPE)
                        dev_err(mdma->dma.dev, "- Group Priority Error\n");
                if (es & MPC_DMA_DMAES_CPE)
                        dev_err(mdma->dma.dev, "- Channel Priority Error\n");
                if (es & MPC_DMA_DMAES_SAE)
                        dev_err(mdma->dma.dev, "- Source Address Error\n");
                if (es & MPC_DMA_DMAES_SOE)
                        dev_err(mdma->dma.dev, "- Source Offset Configuration Error\n");
                if (es & MPC_DMA_DMAES_DAE)
                        dev_err(mdma->dma.dev, "- Destination Address Error\n");
                if (es & MPC_DMA_DMAES_DOE)
                        dev_err(mdma->dma.dev, "- Destination Offset Configuration Error\n");
                if (es & MPC_DMA_DMAES_NCE)
                        dev_err(mdma->dma.dev, "- NBytes/Citter Configuration Error\n");
                if (es & MPC_DMA_DMAES_SGE)
                        dev_err(mdma->dma.dev, "- Scatter/Gather Configuration Error\n");
                if (es & MPC_DMA_DMAES_SBE)
                        dev_err(mdma->dma.dev, "- Source Bus Error\n");
                if (es & MPC_DMA_DMAES_DBE)
                        dev_err(mdma->dma.dev, "- Destination Bus Error\n");
        }

        mpc_dma_process_completed(mdma);
}

/* Submit descriptor to hardware */
static dma_cookie_t mpc_dma_tx_submit(struct dma_async_tx_descriptor *txd)
{
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(txd->chan);
        struct mpc_dma_desc *mdesc;
        unsigned long flags;
        dma_cookie_t cookie;

        mdesc = container_of(txd, struct mpc_dma_desc, desc);

        spin_lock_irqsave(&mchan->lock, flags);

        /* Move descriptor to queue */
        list_move_tail(&mdesc->node, &mchan->queued);

        /* If channel is idle, execute all queued descriptors */
        if (list_empty(&mchan->active))
                mpc_dma_execute(mchan);

        /* Update cookie */
        cookie = dma_cookie_assign(txd);
        spin_unlock_irqrestore(&mchan->lock, flags);

        return cookie;
}

/* Alloc channel resources */
static int mpc_dma_alloc_chan_resources(struct dma_chan *chan)
{
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma_desc *mdesc;
        struct mpc_dma_tcd *tcd;
        dma_addr_t tcd_paddr;
        unsigned long flags;
        LIST_HEAD(descs);
        int i;

        /* Alloc DMA memory for Transfer Control Descriptors */
        tcd = dma_alloc_coherent(mdma->dma.dev,
                        MPC_DMA_DESCRIPTORS * sizeof(struct mpc_dma_tcd),
                                                        &tcd_paddr, GFP_KERNEL);
        if (!tcd)
                return -ENOMEM;

        /* Alloc descriptors for this channel */
        for (i = 0; i < MPC_DMA_DESCRIPTORS; i++) {
                mdesc = kzalloc(sizeof(struct mpc_dma_desc), GFP_KERNEL);
                if (!mdesc) {
                        dev_notice(mdma->dma.dev,
                                "Memory allocation error. Allocated only %u descriptors\n", i);
                        break;
                }

                dma_async_tx_descriptor_init(&mdesc->desc, chan);
                mdesc->desc.flags = DMA_CTRL_ACK;
                mdesc->desc.tx_submit = mpc_dma_tx_submit;

                mdesc->tcd = &tcd[i];
                mdesc->tcd_paddr = tcd_paddr + (i * sizeof(struct mpc_dma_tcd));

                list_add_tail(&mdesc->node, &descs);
        }

        /* Return error only if no descriptors were allocated */
        if (i == 0) {
                dma_free_coherent(mdma->dma.dev,
                        MPC_DMA_DESCRIPTORS * sizeof(struct mpc_dma_tcd),
                                                                tcd, tcd_paddr);
                return -ENOMEM;
        }

        spin_lock_irqsave(&mchan->lock, flags);
        mchan->tcd = tcd;
        mchan->tcd_paddr = tcd_paddr;
        list_splice_tail_init(&descs, &mchan->free);
        spin_unlock_irqrestore(&mchan->lock, flags);

        /* Enable Error Interrupt */
        out_8(&mdma->regs->dmaseei, chan->chan_id);

        return 0;
}

/* Free channel resources */
static void mpc_dma_free_chan_resources(struct dma_chan *chan)
{
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma_desc *mdesc, *tmp;
        struct mpc_dma_tcd *tcd;
        dma_addr_t tcd_paddr;
        unsigned long flags;
        LIST_HEAD(descs);

        spin_lock_irqsave(&mchan->lock, flags);

        /* Channel must be idle */
        BUG_ON(!list_empty(&mchan->prepared));
        BUG_ON(!list_empty(&mchan->queued));
        BUG_ON(!list_empty(&mchan->active));
        BUG_ON(!list_empty(&mchan->completed));

        /* Move data */
        list_splice_tail_init(&mchan->free, &descs);
        tcd = mchan->tcd;
        tcd_paddr = mchan->tcd_paddr;

        spin_unlock_irqrestore(&mchan->lock, flags);

        /* Free DMA memory used by descriptors */
        dma_free_coherent(mdma->dma.dev,
                        MPC_DMA_DESCRIPTORS * sizeof(struct mpc_dma_tcd),
                                                                tcd, tcd_paddr);

        /* Free descriptors */
        list_for_each_entry_safe(mdesc, tmp, &descs, node)
                kfree(mdesc);

        /* Disable Error Interrupt */
        out_8(&mdma->regs->dmaceei, chan->chan_id);
}

/* Send all pending descriptor to hardware */
static void mpc_dma_issue_pending(struct dma_chan *chan)
{
        /*
         * We are posting descriptors to the hardware as soon as
         * they are ready, so this function does nothing.
         */
}

/* Check request completion status */
static enum dma_status
mpc_dma_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
               struct dma_tx_state *txstate)
{
        return dma_cookie_status(chan, cookie, txstate);
}

/* Prepare descriptor for memory to memory copy */
static struct dma_async_tx_descriptor *
mpc_dma_prep_memcpy(struct dma_chan *chan, dma_addr_t dst, dma_addr_t src,
                                        size_t len, unsigned long flags)
{
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma_desc *mdesc = NULL;
        struct mpc_dma_tcd *tcd;
        unsigned long iflags;

        /* Get free descriptor */
        spin_lock_irqsave(&mchan->lock, iflags);
        if (!list_empty(&mchan->free)) {
                mdesc = list_first_entry(&mchan->free, struct mpc_dma_desc,
                                                                        node);
                list_del(&mdesc->node);
        }
        spin_unlock_irqrestore(&mchan->lock, iflags);

        if (!mdesc) {
                /* try to free completed descriptors */
                mpc_dma_process_completed(mdma);
                return NULL;
        }

        mdesc->error = 0;
        mdesc->will_access_peripheral = 0;
        tcd = mdesc->tcd;

        /* Prepare Transfer Control Descriptor for this transaction */
        memset(tcd, 0, sizeof(struct mpc_dma_tcd));

        if (IS_ALIGNED(src | dst | len, 32)) {
                tcd->ssize = MPC_DMA_TSIZE_32;
                tcd->dsize = MPC_DMA_TSIZE_32;
                tcd->soff = 32;
                tcd->doff = 32;
        } else if (!mdma->is_mpc8308 && IS_ALIGNED(src | dst | len, 16)) {
                /* MPC8308 doesn't support 16 byte transfers */
                tcd->ssize = MPC_DMA_TSIZE_16;
                tcd->dsize = MPC_DMA_TSIZE_16;
                tcd->soff = 16;
                tcd->doff = 16;
        } else if (IS_ALIGNED(src | dst | len, 4)) {
                tcd->ssize = MPC_DMA_TSIZE_4;
                tcd->dsize = MPC_DMA_TSIZE_4;
                tcd->soff = 4;
                tcd->doff = 4;
        } else if (IS_ALIGNED(src | dst | len, 2)) {
                tcd->ssize = MPC_DMA_TSIZE_2;
                tcd->dsize = MPC_DMA_TSIZE_2;
                tcd->soff = 2;
                tcd->doff = 2;
        } else {
                tcd->ssize = MPC_DMA_TSIZE_1;
                tcd->dsize = MPC_DMA_TSIZE_1;
                tcd->soff = 1;
                tcd->doff = 1;
        }

        tcd->saddr = src;
        tcd->daddr = dst;
        tcd->nbytes = len;
        tcd->biter = 1;
        tcd->citer = 1;

        /* Place descriptor in prepared list */
        spin_lock_irqsave(&mchan->lock, iflags);
        list_add_tail(&mdesc->node, &mchan->prepared);
        spin_unlock_irqrestore(&mchan->lock, iflags);

        return &mdesc->desc;
}

inline u8 buswidth_to_dmatsize(u8 buswidth)
{
        u8 res;

        for (res = 0; buswidth > 1; buswidth /= 2)
                res++;
        return res;
}

static struct dma_async_tx_descriptor *
mpc_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 mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma_desc *mdesc = NULL;
        dma_addr_t per_paddr;
        u32 tcd_nunits;
        struct mpc_dma_tcd *tcd;
        unsigned long iflags;
        struct scatterlist *sg;
        size_t len;
        int iter, i;

        /* Currently there is no proper support for scatter/gather */
        if (sg_len != 1)
                return NULL;

        if (!is_slave_direction(direction))
                return NULL;

        for_each_sg(sgl, sg, sg_len, i) {
                spin_lock_irqsave(&mchan->lock, iflags);

                mdesc = list_first_entry(&mchan->free,
                                                struct mpc_dma_desc, node);
                if (!mdesc) {
                        spin_unlock_irqrestore(&mchan->lock, iflags);
                        /* Try to free completed descriptors */
                        mpc_dma_process_completed(mdma);
                        return NULL;
                }

                list_del(&mdesc->node);

                if (direction == DMA_DEV_TO_MEM) {
                        per_paddr = mchan->src_per_paddr;
                        tcd_nunits = mchan->src_tcd_nunits;
                } else {
                        per_paddr = mchan->dst_per_paddr;
                        tcd_nunits = mchan->dst_tcd_nunits;
                }

                spin_unlock_irqrestore(&mchan->lock, iflags);

                if (per_paddr == 0 || tcd_nunits == 0)
                        goto err_prep;

                mdesc->error = 0;
                mdesc->will_access_peripheral = 1;

                /* Prepare Transfer Control Descriptor for this transaction */
                tcd = mdesc->tcd;

                memset(tcd, 0, sizeof(struct mpc_dma_tcd));

                if (direction == DMA_DEV_TO_MEM) {
                        tcd->saddr = per_paddr;
                        tcd->daddr = sg_dma_address(sg);

                        if (!IS_ALIGNED(sg_dma_address(sg), mchan->dwidth))
                                goto err_prep;

                        tcd->soff = 0;
                        tcd->doff = mchan->dwidth;
                } else {
                        tcd->saddr = sg_dma_address(sg);
                        tcd->daddr = per_paddr;

                        if (!IS_ALIGNED(sg_dma_address(sg), mchan->swidth))
                                goto err_prep;

                        tcd->soff = mchan->swidth;
                        tcd->doff = 0;
                }

                tcd->ssize = buswidth_to_dmatsize(mchan->swidth);
                tcd->dsize = buswidth_to_dmatsize(mchan->dwidth);

                if (mdma->is_mpc8308) {
                        tcd->nbytes = sg_dma_len(sg);
                        if (!IS_ALIGNED(tcd->nbytes, mchan->swidth))
                                goto err_prep;

                        /* No major loops for MPC8303 */
                        tcd->biter = 1;
                        tcd->citer = 1;
                } else {
                        len = sg_dma_len(sg);
                        tcd->nbytes = tcd_nunits * tcd->ssize;
                        if (!IS_ALIGNED(len, tcd->nbytes))
                                goto err_prep;

                        iter = len / tcd->nbytes;
                        if (iter >= 1 << 15) {
                                /* len is too big */
                                goto err_prep;
                        }
                        /* citer_linkch contains the high bits of iter */
                        tcd->biter = iter & 0x1ff;
                        tcd->biter_linkch = iter >> 9;
                        tcd->citer = tcd->biter;
                        tcd->citer_linkch = tcd->biter_linkch;
                }

                tcd->e_sg = 0;
                tcd->d_req = 1;

                /* Place descriptor in prepared list */
                spin_lock_irqsave(&mchan->lock, iflags);
                list_add_tail(&mdesc->node, &mchan->prepared);
                spin_unlock_irqrestore(&mchan->lock, iflags);
        }

        return &mdesc->desc;

err_prep:
        /* Put the descriptor back */
        spin_lock_irqsave(&mchan->lock, iflags);
        list_add_tail(&mdesc->node, &mchan->free);
        spin_unlock_irqrestore(&mchan->lock, iflags);

        return NULL;
}

inline bool is_buswidth_valid(u8 buswidth, bool is_mpc8308)
{
        switch (buswidth) {
        case 16:
                if (is_mpc8308)
                        return false;
                break;
        case 1:
        case 2:
        case 4:
        case 32:
                break;
        default:
                return false;
        }

        return true;
}

static int mpc_dma_device_config(struct dma_chan *chan,
                                 struct dma_slave_config *cfg)
{
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(&mchan->chan);
        unsigned long flags;

        /*
         * Software constraints:
         *  - only transfers between a peripheral device and memory are
         *     supported
         *  - transfer chunk sizes of 1, 2, 4, 16 (for MPC512x), and 32 bytes
         *     are supported, and, consequently, source addresses and
         *     destination addresses; must be aligned accordingly; furthermore,
         *     for MPC512x SoCs, the transfer size must be aligned on (chunk
         *     size * maxburst)
         *  - during the transfer, the RAM address is incremented by the size
         *     of transfer chunk
         *  - the peripheral port's address is constant during the transfer.
         */

        if (!IS_ALIGNED(cfg->src_addr, cfg->src_addr_width) ||
            !IS_ALIGNED(cfg->dst_addr, cfg->dst_addr_width)) {
                return -EINVAL;
        }

        if (!is_buswidth_valid(cfg->src_addr_width, mdma->is_mpc8308) ||
            !is_buswidth_valid(cfg->dst_addr_width, mdma->is_mpc8308))
                return -EINVAL;

        spin_lock_irqsave(&mchan->lock, flags);

        mchan->src_per_paddr = cfg->src_addr;
        mchan->src_tcd_nunits = cfg->src_maxburst;
        mchan->swidth = cfg->src_addr_width;
        mchan->dst_per_paddr = cfg->dst_addr;
        mchan->dst_tcd_nunits = cfg->dst_maxburst;
        mchan->dwidth = cfg->dst_addr_width;

        /* Apply defaults */
        if (mchan->src_tcd_nunits == 0)
                mchan->src_tcd_nunits = 1;
        if (mchan->dst_tcd_nunits == 0)
                mchan->dst_tcd_nunits = 1;

        spin_unlock_irqrestore(&mchan->lock, flags);

        return 0;
}

static int mpc_dma_device_terminate_all(struct dma_chan *chan)
{
        struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
        struct mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
        unsigned long flags;

        /* Disable channel requests */
        spin_lock_irqsave(&mchan->lock, flags);

        out_8(&mdma->regs->dmacerq, chan->chan_id);
        list_splice_tail_init(&mchan->prepared, &mchan->free);
        list_splice_tail_init(&mchan->queued, &mchan->free);
        list_splice_tail_init(&mchan->active, &mchan->free);

        spin_unlock_irqrestore(&mchan->lock, flags);

        return 0;
}

static int mpc_dma_probe(struct platform_device *op)
{
        struct device_node *dn = op->dev.of_node;
        struct device *dev = &op->dev;
        struct dma_device *dma;
        struct mpc_dma *mdma;
        struct mpc_dma_chan *mchan;
        struct resource res;
        ulong regs_start, regs_size;
        int retval, i;
        u8 chancnt;

        mdma = devm_kzalloc(dev, sizeof(struct mpc_dma), GFP_KERNEL);
        if (!mdma) {
                retval = -ENOMEM;
                goto err;
        }

        mdma->irq = irq_of_parse_and_map(dn, 0);
        if (!mdma->irq) {
                dev_err(dev, "Error mapping IRQ!\n");
                retval = -EINVAL;
                goto err;
        }

        if (of_device_is_compatible(dn, "fsl,mpc8308-dma")) {
                mdma->is_mpc8308 = 1;
                mdma->irq2 = irq_of_parse_and_map(dn, 1);
                if (!mdma->irq2) {
                        dev_err(dev, "Error mapping IRQ!\n");
                        retval = -EINVAL;
                        goto err_dispose1;
                }
        }

        retval = of_address_to_resource(dn, 0, &res);
        if (retval) {
                dev_err(dev, "Error parsing memory region!\n");
                goto err_dispose2;
        }

        regs_start = res.start;
        regs_size = resource_size(&res);

        if (!devm_request_mem_region(dev, regs_start, regs_size, DRV_NAME)) {
                dev_err(dev, "Error requesting memory region!\n");
                retval = -EBUSY;
                goto err_dispose2;
        }

        mdma->regs = devm_ioremap(dev, regs_start, regs_size);
        if (!mdma->regs) {
                dev_err(dev, "Error mapping memory region!\n");
                retval = -ENOMEM;
                goto err_dispose2;
        }

        mdma->tcd = (struct mpc_dma_tcd *)((u8 *)(mdma->regs)
                                                        + MPC_DMA_TCD_OFFSET);

        retval = request_irq(mdma->irq, &mpc_dma_irq, 0, DRV_NAME, mdma);
        if (retval) {
                dev_err(dev, "Error requesting IRQ!\n");
                retval = -EINVAL;
                goto err_dispose2;
        }

        if (mdma->is_mpc8308) {
                retval = request_irq(mdma->irq2, &mpc_dma_irq, 0,
                                                        DRV_NAME, mdma);
                if (retval) {
                        dev_err(dev, "Error requesting IRQ2!\n");
                        retval = -EINVAL;
                        goto err_free1;
                }
        }

        spin_lock_init(&mdma->error_status_lock);

        dma = &mdma->dma;
        dma->dev = dev;
        dma->device_alloc_chan_resources = mpc_dma_alloc_chan_resources;
        dma->device_free_chan_resources = mpc_dma_free_chan_resources;
        dma->device_issue_pending = mpc_dma_issue_pending;
        dma->device_tx_status = mpc_dma_tx_status;
        dma->device_prep_dma_memcpy = mpc_dma_prep_memcpy;
        dma->device_prep_slave_sg = mpc_dma_prep_slave_sg;
        dma->device_config = mpc_dma_device_config;
        dma->device_terminate_all = mpc_dma_device_terminate_all;

        INIT_LIST_HEAD(&dma->channels);
        dma_cap_set(DMA_MEMCPY, dma->cap_mask);
        dma_cap_set(DMA_SLAVE, dma->cap_mask);

        if (mdma->is_mpc8308)
                chancnt = MPC8308_DMACHAN_MAX;
        else
                chancnt = MPC512x_DMACHAN_MAX;

        for (i = 0; i < chancnt; i++) {
                mchan = &mdma->channels[i];

                mchan->chan.device = dma;

                dma_cookie_init(&mchan->chan);

                INIT_LIST_HEAD(&mchan->free);
                INIT_LIST_HEAD(&mchan->prepared);
                INIT_LIST_HEAD(&mchan->queued);
                INIT_LIST_HEAD(&mchan->active);
                INIT_LIST_HEAD(&mchan->completed);

                spin_lock_init(&mchan->lock);
                list_add_tail(&mchan->chan.device_node, &dma->channels);
        }

        tasklet_setup(&mdma->tasklet, mpc_dma_tasklet);

        /*
         * Configure DMA Engine:
         * - Dynamic clock,
         * - Round-robin group arbitration,
         * - Round-robin channel arbitration.
         */
        if (mdma->is_mpc8308) {
                /* MPC8308 has 16 channels and lacks some registers */
                out_be32(&mdma->regs->dmacr, MPC_DMA_DMACR_ERCA);

                /* enable snooping */
                out_be32(&mdma->regs->dmagpor, MPC_DMA_DMAGPOR_SNOOP_ENABLE);
                /* Disable error interrupts */
                out_be32(&mdma->regs->dmaeeil, 0);

                /* Clear interrupts status */
                out_be32(&mdma->regs->dmaintl, 0xFFFF);
                out_be32(&mdma->regs->dmaerrl, 0xFFFF);
        } else {
                out_be32(&mdma->regs->dmacr, MPC_DMA_DMACR_EDCG |
                                                MPC_DMA_DMACR_ERGA |
                                                MPC_DMA_DMACR_ERCA);

                /* Disable hardware DMA requests */
                out_be32(&mdma->regs->dmaerqh, 0);
                out_be32(&mdma->regs->dmaerql, 0);

                /* Disable error interrupts */
                out_be32(&mdma->regs->dmaeeih, 0);
                out_be32(&mdma->regs->dmaeeil, 0);

                /* Clear interrupts status */
                out_be32(&mdma->regs->dmainth, 0xFFFFFFFF);
                out_be32(&mdma->regs->dmaintl, 0xFFFFFFFF);
                out_be32(&mdma->regs->dmaerrh, 0xFFFFFFFF);
                out_be32(&mdma->regs->dmaerrl, 0xFFFFFFFF);

                /* Route interrupts to IPIC */
                out_be32(&mdma->regs->dmaihsa, 0);
                out_be32(&mdma->regs->dmailsa, 0);
        }

        /* Register DMA engine */
        dev_set_drvdata(dev, mdma);
        retval = dma_async_device_register(dma);
        if (retval)
                goto err_free2;

        /* Register with OF helpers for DMA lookups (nonfatal) */
        if (dev->of_node) {
                retval = of_dma_controller_register(dev->of_node,
                                                of_dma_xlate_by_chan_id, mdma);
                if (retval)
                        dev_warn(dev, "Could not register for OF lookup\n");
        }

        return 0;

err_free2:
        if (mdma->is_mpc8308)
                free_irq(mdma->irq2, mdma);
err_free1:
        free_irq(mdma->irq, mdma);
err_dispose2:
        if (mdma->is_mpc8308)
                irq_dispose_mapping(mdma->irq2);
err_dispose1:
        irq_dispose_mapping(mdma->irq);
err:
        return retval;
}

static int mpc_dma_remove(struct platform_device *op)
{
        struct device *dev = &op->dev;
        struct mpc_dma *mdma = dev_get_drvdata(dev);

        if (dev->of_node)
                of_dma_controller_free(dev->of_node);
        dma_async_device_unregister(&mdma->dma);
        if (mdma->is_mpc8308) {
                free_irq(mdma->irq2, mdma);
                irq_dispose_mapping(mdma->irq2);
        }
        free_irq(mdma->irq, mdma);
        irq_dispose_mapping(mdma->irq);
        tasklet_kill(&mdma->tasklet);

        return 0;
}

static const struct of_device_id mpc_dma_match[] = {
        { .compatible = "fsl,mpc5121-dma", },
        { .compatible = "fsl,mpc8308-dma", },
        {},
};
MODULE_DEVICE_TABLE(of, mpc_dma_match);

static struct platform_driver mpc_dma_driver = {
        .probe          = mpc_dma_probe,
        .remove         = mpc_dma_remove,
        .driver = {
                .name = DRV_NAME,
                .of_match_table = mpc_dma_match,
        },
};

module_platform_driver(mpc_dma_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Piotr Ziecik <kosmo@semihalf.com>");