Archipelago » qemu

/*

 * QEMU ETRAX DMA Controller.

 *

 * Copyright (c) 2008 Edgar E. Iglesias, Axis Communications AB.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include <stdio.h>

#include <sys/time.h>

#include "hw.h"

#include "etraxfs_dma.h"

#define D(x)

#define RW_DATA           0x0

#define RW_SAVED_DATA     0x58

#define RW_SAVED_DATA_BUF 0x5c

#define RW_GROUP          0x60

#define RW_GROUP_DOWN     0x7c

#define RW_CMD            0x80

#define RW_CFG            0x84

#define RW_STAT           0x88

#define RW_INTR_MASK      0x8c

#define RW_ACK_INTR       0x90

#define R_INTR            0x94

#define R_MASKED_INTR     0x98

#define RW_STREAM_CMD     0x9c

#define DMA_REG_MAX   0x100

/* descriptors */

// ------------------------------------------------------------ dma_descr_group

typedef struct dma_descr_group {

  struct dma_descr_group       *next;

  unsigned                      eol        : 1;

  unsigned                      tol        : 1;

  unsigned                      bol        : 1;

  unsigned                                 : 1;

  unsigned                      intr       : 1;

  unsigned                                 : 2;

  unsigned                      en         : 1;

  unsigned                                 : 7;

  unsigned                      dis        : 1;

  unsigned                      md         : 16;

  struct dma_descr_group       *up;

  union {

    struct dma_descr_context   *context;

    struct dma_descr_group     *group;

  }                             down;

} dma_descr_group;

// ---------------------------------------------------------- dma_descr_context

typedef struct dma_descr_context {

  struct dma_descr_context     *next;

  unsigned                      eol        : 1;

  unsigned                                 : 3;

  unsigned                      intr       : 1;

  unsigned                                 : 1;

  unsigned                      store_mode : 1;

  unsigned                      en         : 1;

  unsigned                                 : 7;

  unsigned                      dis        : 1;

  unsigned                      md0        : 16;

  unsigned                      md1;

  unsigned                      md2;

  unsigned                      md3;

  unsigned                      md4;

  struct dma_descr_data        *saved_data;

  char                         *saved_data_buf;

} dma_descr_context;

// ------------------------------------------------------------- dma_descr_data

typedef struct dma_descr_data {

  struct dma_descr_data        *next;

  char                         *buf;

  unsigned                      eol        : 1;

  unsigned                                 : 2;

  unsigned                      out_eop    : 1;

  unsigned                      intr       : 1;

  unsigned                      wait       : 1;

  unsigned                                 : 2;

  unsigned                                 : 3;

  unsigned                      in_eop     : 1;

  unsigned                                 : 4;

  unsigned                      md         : 16;

  char                         *after;

} dma_descr_data;

/* Constants */

enum {

  regk_dma_ack_pkt                         = 0x00000100,

  regk_dma_anytime                         = 0x00000001,

  regk_dma_array                           = 0x00000008,

  regk_dma_burst                           = 0x00000020,

  regk_dma_client                          = 0x00000002,

  regk_dma_copy_next                       = 0x00000010,

  regk_dma_copy_up                         = 0x00000020,

  regk_dma_data_at_eol                     = 0x00000001,

  regk_dma_dis_c                           = 0x00000010,

  regk_dma_dis_g                           = 0x00000020,

  regk_dma_idle                            = 0x00000001,

  regk_dma_intern                          = 0x00000004,

  regk_dma_load_c                          = 0x00000200,

  regk_dma_load_c_n                        = 0x00000280,

  regk_dma_load_c_next                     = 0x00000240,

  regk_dma_load_d                          = 0x00000140,

  regk_dma_load_g                          = 0x00000300,

  regk_dma_load_g_down                     = 0x000003c0,

  regk_dma_load_g_next                     = 0x00000340,

  regk_dma_load_g_up                       = 0x00000380,

  regk_dma_next_en                         = 0x00000010,

  regk_dma_next_pkt                        = 0x00000010,

  regk_dma_no                              = 0x00000000,

  regk_dma_only_at_wait                    = 0x00000000,

  regk_dma_restore                         = 0x00000020,

  regk_dma_rst                             = 0x00000001,

  regk_dma_running                         = 0x00000004,

  regk_dma_rw_cfg_default                  = 0x00000000,

  regk_dma_rw_cmd_default                  = 0x00000000,

  regk_dma_rw_intr_mask_default            = 0x00000000,

  regk_dma_rw_stat_default                 = 0x00000101,

  regk_dma_rw_stream_cmd_default           = 0x00000000,

  regk_dma_save_down                       = 0x00000020,

  regk_dma_save_up                         = 0x00000020,

  regk_dma_set_reg                         = 0x00000050,

  regk_dma_set_w_size1                     = 0x00000190,

  regk_dma_set_w_size2                     = 0x000001a0,

  regk_dma_set_w_size4                     = 0x000001c0,

  regk_dma_stopped                         = 0x00000002,

  regk_dma_store_c                         = 0x00000002,

  regk_dma_store_descr                     = 0x00000000,

  regk_dma_store_g                         = 0x00000004,

  regk_dma_store_md                        = 0x00000001,

  regk_dma_sw                              = 0x00000008,

  regk_dma_update_down                     = 0x00000020,

  regk_dma_yes                             = 0x00000001

};

enum dma_ch_state

{

        RST = 0,

        STOPPED = 2,

        RUNNING = 4

};

struct fs_dma_channel

{

        int regmap;

        qemu_irq *irq;

        struct etraxfs_dma_client *client;

        /* Internal status.  */

        int stream_cmd_src;

        enum dma_ch_state state;

        unsigned int input : 1;

        unsigned int eol : 1;

        struct dma_descr_group current_g;

        struct dma_descr_context current_c;

        struct dma_descr_data current_d;

        /* Controll registers.  */

        uint32_t regs[DMA_REG_MAX];

};

struct fs_dma_ctrl

{

        CPUState *env;

        target_phys_addr_t base;

        int nr_channels;

        struct fs_dma_channel *channels;

};

static inline uint32_t channel_reg(struct fs_dma_ctrl *ctrl, int c, int reg)

{

        return ctrl->channels[c].regs[reg];

}

static inline int channel_stopped(struct fs_dma_ctrl *ctrl, int c)

{

        return channel_reg(ctrl, c, RW_CFG) & 2;

}

static inline int channel_en(struct fs_dma_ctrl *ctrl, int c)

{

        return (channel_reg(ctrl, c, RW_CFG) & 1)

                && ctrl->channels[c].client;

}

static inline int fs_channel(target_phys_addr_t base, target_phys_addr_t addr)

{

        /* Every channel has a 0x2000 ctrl register map.  */

        return (addr - base) >> 13;

}

#ifdef USE_THIS_DEAD_CODE

static void channel_load_g(struct fs_dma_ctrl *ctrl, int c)

{

        target_phys_addr_t addr = channel_reg(ctrl, c, RW_GROUP);

        /* Load and decode. FIXME: handle endianness.  */

        cpu_physical_memory_read (addr, 

                                  (void *) &ctrl->channels[c].current_g, 

                                  sizeof ctrl->channels[c].current_g);

}

static void dump_c(int ch, struct dma_descr_context *c)

{

        printf("%s ch=%d\n", __func__, ch);

        printf("next=%p\n", c->next);

        printf("saved_data=%p\n", c->saved_data);

        printf("saved_data_buf=%p\n", c->saved_data_buf);

        printf("eol=%x\n", (uint32_t) c->eol);

}

static void dump_d(int ch, struct dma_descr_data *d)

{

        printf("%s ch=%d\n", __func__, ch);

        printf("next=%p\n", d->next);

        printf("buf=%p\n", d->buf);

        printf("after=%p\n", d->after);

        printf("intr=%x\n", (uint32_t) d->intr);

        printf("out_eop=%x\n", (uint32_t) d->out_eop);

        printf("in_eop=%x\n", (uint32_t) d->in_eop);

        printf("eol=%x\n", (uint32_t) d->eol);

}

#endif

static void channel_load_c(struct fs_dma_ctrl *ctrl, int c)

{

        target_phys_addr_t addr = channel_reg(ctrl, c, RW_GROUP_DOWN);

        /* Load and decode. FIXME: handle endianness.  */

        cpu_physical_memory_read (addr, 

                                  (void *) &ctrl->channels[c].current_c, 

                                  sizeof ctrl->channels[c].current_c);

        D(dump_c(c, &ctrl->channels[c].current_c));

        /* I guess this should update the current pos.  */

        ctrl->channels[c].regs[RW_SAVED_DATA] =

                (uint32_t)(unsigned long)ctrl->channels[c].current_c.saved_data;

        ctrl->channels[c].regs[RW_SAVED_DATA_BUF] =

                (uint32_t)(unsigned long)ctrl->channels[c].current_c.saved_data_buf;

}

static void channel_load_d(struct fs_dma_ctrl *ctrl, int c)

{

        target_phys_addr_t addr = channel_reg(ctrl, c, RW_SAVED_DATA);

        /* Load and decode. FIXME: handle endianness.  */

        D(printf("%s ch=%d addr=%x\n", __func__, c, addr));

        cpu_physical_memory_read (addr,

                                  (void *) &ctrl->channels[c].current_d, 

                                  sizeof ctrl->channels[c].current_d);

        D(dump_d(c, &ctrl->channels[c].current_d));

        ctrl->channels[c].regs[RW_DATA] = addr;

}

static void channel_store_c(struct fs_dma_ctrl *ctrl, int c)

{

        target_phys_addr_t addr = channel_reg(ctrl, c, RW_GROUP_DOWN);

        /* Encode and store. FIXME: handle endianness.  */

        D(printf("%s ch=%d addr=%x\n", __func__, c, addr));

        D(dump_d(c, &ctrl->channels[c].current_d));

        cpu_physical_memory_write (addr,

                                  (void *) &ctrl->channels[c].current_c,

                                  sizeof ctrl->channels[c].current_c);

}

static void channel_store_d(struct fs_dma_ctrl *ctrl, int c)

{

        target_phys_addr_t addr = channel_reg(ctrl, c, RW_SAVED_DATA);

        /* Encode and store. FIXME: handle endianness.  */

        D(printf("%s ch=%d addr=%x\n", __func__, c, addr));

        cpu_physical_memory_write (addr,

                                  (void *) &ctrl->channels[c].current_d, 

                                  sizeof ctrl->channels[c].current_d);

}

static inline void channel_stop(struct fs_dma_ctrl *ctrl, int c)

{

        /* FIXME:  */

}

static inline void channel_start(struct fs_dma_ctrl *ctrl, int c)

{

        if (ctrl->channels[c].client)

        {

                ctrl->channels[c].eol = 0;

                ctrl->channels[c].state = RUNNING;

        } else

                printf("WARNING: starting DMA ch %d with no client\n", c);

}

static void channel_continue(struct fs_dma_ctrl *ctrl, int c)

{

        if (!channel_en(ctrl, c) 

            || channel_stopped(ctrl, c)

            || ctrl->channels[c].state != RUNNING

            /* Only reload the current data descriptor if it has eol set.  */

            || !ctrl->channels[c].current_d.eol) {

                D(printf("continue failed ch=%d state=%d stopped=%d en=%d eol=%d\n", 

                         c, ctrl->channels[c].state,

                         channel_stopped(ctrl, c),

                         channel_en(ctrl,c),

                         ctrl->channels[c].eol));

                D(dump_d(c, &ctrl->channels[c].current_d));

                return;

        }

        /* Reload the current descriptor.  */

        channel_load_d(ctrl, c);

        /* If the current descriptor cleared the eol flag and we had already

           reached eol state, do the continue.  */

        if (!ctrl->channels[c].current_d.eol && ctrl->channels[c].eol) {

                D(printf("continue %d ok %p\n", c,

                         ctrl->channels[c].current_d.next));

                ctrl->channels[c].regs[RW_SAVED_DATA] =

                        (uint32_t)(unsigned long)ctrl->channels[c].current_d.next;

                channel_load_d(ctrl, c);

                channel_start(ctrl, c);

        }

        ctrl->channels[c].regs[RW_SAVED_DATA_BUF] =

                (uint32_t)(unsigned long)ctrl->channels[c].current_d.buf;

}

static void channel_stream_cmd(struct fs_dma_ctrl *ctrl, int c, uint32_t v)

{

        unsigned int cmd = v & ((1 << 10) - 1);

        D(printf("%s ch=%d cmd=%x\n",

                 __func__, c, cmd));

        if (cmd & regk_dma_load_d) {

                channel_load_d(ctrl, c);

                if (cmd & regk_dma_burst)

                        channel_start(ctrl, c);

        }

        if (cmd & regk_dma_load_c) {

                channel_load_c(ctrl, c);

                channel_start(ctrl, c);

        }

}

static void channel_update_irq(struct fs_dma_ctrl *ctrl, int c)

{

        D(printf("%s %d\n", __func__, c));

        ctrl->channels[c].regs[R_INTR] &=

                ~(ctrl->channels[c].regs[RW_ACK_INTR]);

        ctrl->channels[c].regs[R_MASKED_INTR] =

                ctrl->channels[c].regs[R_INTR]

                & ctrl->channels[c].regs[RW_INTR_MASK];

        D(printf("%s: chan=%d masked_intr=%x\n", __func__, 

                 c,

                 ctrl->channels[c].regs[R_MASKED_INTR]));

        if (ctrl->channels[c].regs[R_MASKED_INTR])

                qemu_irq_raise(ctrl->channels[c].irq[0]);

        else

                qemu_irq_lower(ctrl->channels[c].irq[0]);

}

static void channel_out_run(struct fs_dma_ctrl *ctrl, int c)

{

        uint32_t len;

        uint32_t saved_data_buf;

        unsigned char buf[2 * 1024];

        if (ctrl->channels[c].eol == 1)

                return;

        saved_data_buf = channel_reg(ctrl, c, RW_SAVED_DATA_BUF);

        D(fprintf(logfile, "ch=%d buf=%x after=%x saved_data_buf=%x\n",

                 c,

                 (uint32_t)ctrl->channels[c].current_d.buf,

                 (uint32_t)ctrl->channels[c].current_d.after,

                 saved_data_buf));

        len = (uint32_t)(unsigned long) ctrl->channels[c].current_d.after;

        len -= saved_data_buf;

        if (len > sizeof buf)

                len = sizeof buf;

        cpu_physical_memory_read (saved_data_buf, buf, len);

        D(printf("channel %d pushes %x %u bytes\n", c, 

                 saved_data_buf, len));

        if (ctrl->channels[c].client->client.push)

                ctrl->channels[c].client->client.push(

                        ctrl->channels[c].client->client.opaque, buf, len);

        else

                printf("WARNING: DMA ch%d dataloss, no attached client.\n", c);

        saved_data_buf += len;

        if (saved_data_buf ==

            (uint32_t)(unsigned long)ctrl->channels[c].current_d.after) {

                /* Done. Step to next.  */

                if (ctrl->channels[c].current_d.out_eop) {

                        /* TODO: signal eop to the client.  */

                        D(printf("signal eop\n"));

                }

                if (ctrl->channels[c].current_d.intr) {

                        /* TODO: signal eop to the client.  */

                        /* data intr.  */

                        D(printf("signal intr\n"));

                        ctrl->channels[c].regs[R_INTR] |= (1 << 2);

                        channel_update_irq(ctrl, c);

                }

                if (ctrl->channels[c].current_d.eol) {

                        D(printf("channel %d EOL\n", c));

                        ctrl->channels[c].eol = 1;

                        /* Mark the context as disabled.  */

                        ctrl->channels[c].current_c.dis = 1;

                        channel_store_c(ctrl, c);

                        channel_stop(ctrl, c);

                } else {

                        ctrl->channels[c].regs[RW_SAVED_DATA] =

                                (uint32_t)(unsigned long) ctrl->channels[c].current_d.next;

                        /* Load new descriptor.  */

                        channel_load_d(ctrl, c);

                        saved_data_buf = (uint32_t)(unsigned long)

                                ctrl->channels[c].current_d.buf;

                }

                channel_store_d(ctrl, c);

                ctrl->channels[c].regs[RW_SAVED_DATA_BUF] = saved_data_buf;

                D(dump_d(c, &ctrl->channels[c].current_d));

        }

        ctrl->channels[c].regs[RW_SAVED_DATA_BUF] = saved_data_buf;

}

static int channel_in_process(struct fs_dma_ctrl *ctrl, int c, 

                              unsigned char *buf, int buflen, int eop)

{

        uint32_t len;

        uint32_t saved_data_buf;

        if (ctrl->channels[c].eol == 1)

                return 0;

        saved_data_buf = channel_reg(ctrl, c, RW_SAVED_DATA_BUF);

        len = (uint32_t)(unsigned long) ctrl->channels[c].current_d.after;

        len -= saved_data_buf;

        if (len > buflen)

                len = buflen;

        cpu_physical_memory_write (saved_data_buf, buf, len);

        saved_data_buf += len;

        if (saved_data_buf ==

            (uint32_t)(unsigned long)ctrl->channels[c].current_d.after

            || eop) {

                uint32_t r_intr = ctrl->channels[c].regs[R_INTR];

                D(printf("in dscr end len=%d\n", 

                         ctrl->channels[c].current_d.after

                         - ctrl->channels[c].current_d.buf));

                ctrl->channels[c].current_d.after = 

                        (void *)(unsigned long) saved_data_buf;

                /* Done. Step to next.  */

                if (ctrl->channels[c].current_d.intr) {

                        /* TODO: signal eop to the client.  */

                        /* data intr.  */

                        ctrl->channels[c].regs[R_INTR] |= 3;

                }

                if (eop) {

                        ctrl->channels[c].current_d.in_eop = 1;

                        ctrl->channels[c].regs[R_INTR] |= 8;

                }

                if (r_intr != ctrl->channels[c].regs[R_INTR])

                        channel_update_irq(ctrl, c);

                channel_store_d(ctrl, c);

                D(dump_d(c, &ctrl->channels[c].current_d));

                if (ctrl->channels[c].current_d.eol) {

                        D(printf("channel %d EOL\n", c));

                        ctrl->channels[c].eol = 1;

                        /* Mark the context as disabled.  */

                        ctrl->channels[c].current_c.dis = 1;

                        channel_store_c(ctrl, c);

                        channel_stop(ctrl, c);

                } else {

                        ctrl->channels[c].regs[RW_SAVED_DATA] =

                                (uint32_t)(unsigned long) ctrl->channels[c].current_d.next;

                        /* Load new descriptor.  */

                        channel_load_d(ctrl, c);

                        saved_data_buf = (uint32_t)(unsigned long)

                                ctrl->channels[c].current_d.buf;

                }

        }

        ctrl->channels[c].regs[RW_SAVED_DATA_BUF] = saved_data_buf;

        return len;

}

static inline void channel_in_run(struct fs_dma_ctrl *ctrl, int c)

{

        if (ctrl->channels[c].client->client.pull)

                ctrl->channels[c].client->client.pull(

                        ctrl->channels[c].client->client.opaque);

}

static uint32_t dma_rinvalid (void *opaque, target_phys_addr_t addr)

{

        struct fs_dma_ctrl *ctrl = opaque;

        CPUState *env = ctrl->env;

        cpu_abort(env, "Unsupported short access. reg=" TARGET_FMT_plx "\n",

                  addr);

        return 0;

}

static uint32_t

dma_readl (void *opaque, target_phys_addr_t addr)

{

        struct fs_dma_ctrl *ctrl = opaque;

        int c;

        uint32_t r = 0;

        /* Make addr relative to this instances base.  */

        c = fs_channel(ctrl->base, addr);

        addr &= 0x1fff;

        switch (addr)

        {

                case RW_STAT:

                        r = ctrl->channels[c].state & 7;

                        r |= ctrl->channels[c].eol << 5;

                        r |= ctrl->channels[c].stream_cmd_src << 8;

                        break;

                default:

                        r = ctrl->channels[c].regs[addr];

                        D(printf ("%s c=%d addr=%x\n",

                                  __func__, c, addr));

                        break;

        }

        return r;

}

static void

dma_winvalid (void *opaque, target_phys_addr_t addr, uint32_t value)

{

        struct fs_dma_ctrl *ctrl = opaque;

        CPUState *env = ctrl->env;

        cpu_abort(env, "Unsupported short access. reg=" TARGET_FMT_plx "\n",

                  addr);

}

static void

dma_writel (void *opaque, target_phys_addr_t addr, uint32_t value)

{

        struct fs_dma_ctrl *ctrl = opaque;

        int c;

        /* Make addr relative to this instances base.  */

        c = fs_channel(ctrl->base, addr);

        addr &= 0x1fff;

        switch (addr)

        {

                case RW_DATA:

                        ctrl->channels[c].regs[addr] = value;

                        break;

                case RW_CFG:

                        ctrl->channels[c].regs[addr] = value;

                        break;

                case RW_CMD:

                        /* continue.  */

                        ctrl->channels[c].regs[addr] = value;

                        channel_continue(ctrl, c);

                        break;

                case RW_SAVED_DATA:

                case RW_SAVED_DATA_BUF:

                case RW_GROUP:

                case RW_GROUP_DOWN:

                        ctrl->channels[c].regs[addr] = value;

                        break;

                case RW_ACK_INTR:

                case RW_INTR_MASK:

                        ctrl->channels[c].regs[addr] = value;

                        channel_update_irq(ctrl, c);

                        if (addr == RW_ACK_INTR)

                                ctrl->channels[c].regs[RW_ACK_INTR] = 0;

                        break;

                case RW_STREAM_CMD:

                        ctrl->channels[c].regs[addr] = value;

                        D(printf("stream_cmd ch=%d\n", c));

                        channel_stream_cmd(ctrl, c, value);

                        break;

                default:

                        D(printf ("%s c=%d %x %x\n", __func__, c, addr));

                        break;

        }

}

static CPUReadMemoryFunc *dma_read[] = {

        &dma_rinvalid,

        &dma_rinvalid,

        &dma_readl,

};

static CPUWriteMemoryFunc *dma_write[] = {

        &dma_winvalid,

        &dma_winvalid,

        &dma_writel,

};

void etraxfs_dmac_run(void *opaque)

{

        struct fs_dma_ctrl *ctrl = opaque;

        int i;

        int p = 0;

        for (i = 0; 

             i < ctrl->nr_channels;

             i++)

        {

                if (ctrl->channels[i].state == RUNNING)

                {

                        p++;

                        if (ctrl->channels[i].input)

                                channel_in_run(ctrl, i);

                        else

                                channel_out_run(ctrl, i);

                }

        }

}

int etraxfs_dmac_input(struct etraxfs_dma_client *client, 

                       void *buf, int len, int eop)

{

        return channel_in_process(client->ctrl, client->channel, 

                                  buf, len, eop);

}

/* Connect an IRQ line with a channel.  */

void etraxfs_dmac_connect(void *opaque, int c, qemu_irq *line, int input)

{

        struct fs_dma_ctrl *ctrl = opaque;

        ctrl->channels[c].irq = line;

        ctrl->channels[c].input = input;

}

void etraxfs_dmac_connect_client(void *opaque, int c, 

                                 struct etraxfs_dma_client *cl)

{

        struct fs_dma_ctrl *ctrl = opaque;

        cl->ctrl = ctrl;

        cl->channel = c;

        ctrl->channels[c].client = cl;

}

static void *etraxfs_dmac;

void DMA_run(void)

{

        if (etraxfs_dmac)

                etraxfs_dmac_run(etraxfs_dmac);

}

void *etraxfs_dmac_init(CPUState *env, 

                        target_phys_addr_t base, int nr_channels)

{

        struct fs_dma_ctrl *ctrl = NULL;

        int i;

        ctrl = qemu_mallocz(sizeof *ctrl);

        if (!ctrl)

                return NULL;

        ctrl->base = base;

        ctrl->env = env;

        ctrl->nr_channels = nr_channels;

        ctrl->channels = qemu_mallocz(sizeof ctrl->channels[0] * nr_channels);

        if (!ctrl->channels)

                goto err;

        for (i = 0; i < nr_channels; i++)

        {

                ctrl->channels[i].regmap = cpu_register_io_memory(0,

                                                                  dma_read, 

                                                                  dma_write, 

                                                                  ctrl);

                cpu_register_physical_memory (base + i * 0x2000,

                                              sizeof ctrl->channels[i].regs, 

                                              ctrl->channels[i].regmap);

        }

        /* Hax, we only support one DMA controller at a time.  */

        etraxfs_dmac = ctrl;

        return ctrl;

  err:

        qemu_free(ctrl->channels);

        qemu_free(ctrl);

        return NULL;

}