qemu/hw/etraxfs_dma.c

/*
 * 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;
}