hw/milkymist-minimac.c - qemu - Git at Google

 /*
  *  QEMU model of the Milkymist minimac block.
  *
  *  Copyright (c) 2010 Michael Walle <michael@walle.cc>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  *
  *
  * Specification available at:
  *   http://www.milkymist.org/socdoc/minimac.pdf
  *
  */

 #include "hw.h"
 #include "sysbus.h"
 #include "trace.h"
 #include "net.h"
 #include "qemu-error.h"

 #include <zlib.h>

 enum {
     R_SETUP = 0,
     R_MDIO,
     R_STATE0,
     R_ADDR0,
     R_COUNT0,
     R_STATE1,
     R_ADDR1,
     R_COUNT1,
     R_STATE2,
     R_ADDR2,
     R_COUNT2,
     R_STATE3,
     R_ADDR3,
     R_COUNT3,
     R_TXADDR,
     R_TXCOUNT,
     R_MAX
 };

 enum {
     SETUP_RX_RST = (1<<0),
     SETUP_TX_RST = (1<<2),
 };

 enum {
     MDIO_DO  = (1<<0),
     MDIO_DI  = (1<<1),
     MDIO_OE  = (1<<2),
     MDIO_CLK = (1<<3),
 };

 enum {
     STATE_EMPTY   = 0,
     STATE_LOADED  = 1,
     STATE_PENDING = 2,
 };

 enum {
     MDIO_OP_WRITE = 1,
     MDIO_OP_READ  = 2,
 };

 enum mdio_state {
     MDIO_STATE_IDLE,
     MDIO_STATE_READING,
     MDIO_STATE_WRITING,
 };

 enum {
     R_PHY_ID1  = 2,
     R_PHY_ID2  = 3,
     R_PHY_MAX  = 32
 };

 #define MINIMAC_MTU 1530

 struct MilkymistMinimacMdioState {
     int last_clk;
     int count;
     uint32_t data;
     uint16_t data_out;
     int state;

     uint8_t phy_addr;
     uint8_t reg_addr;
 };
 typedef struct MilkymistMinimacMdioState MilkymistMinimacMdioState;

 struct MilkymistMinimacState {
     SysBusDevice busdev;
     NICState *nic;
     NICConf conf;
     char *phy_model;

     qemu_irq rx_irq;
     qemu_irq tx_irq;

     uint32_t regs[R_MAX];

     MilkymistMinimacMdioState mdio;

     uint16_t phy_regs[R_PHY_MAX];
 };
 typedef struct MilkymistMinimacState MilkymistMinimacState;

 static const uint8_t preamble_sfd[] = {
         0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xd5
 };

 static void minimac_mdio_write_reg(MilkymistMinimacState *s,
         uint8_t phy_addr, uint8_t reg_addr, uint16_t value)
 {
     trace_milkymist_minimac_mdio_write(phy_addr, reg_addr, value);

     /* nop */
 }

 static uint16_t minimac_mdio_read_reg(MilkymistMinimacState *s,
         uint8_t phy_addr, uint8_t reg_addr)
 {
     uint16_t r = s->phy_regs[reg_addr];

     trace_milkymist_minimac_mdio_read(phy_addr, reg_addr, r);

     return r;
 }

 static void minimac_update_mdio(MilkymistMinimacState *s)
 {
     MilkymistMinimacMdioState *m = &s->mdio;

     /* detect rising clk edge */
     if (m->last_clk == 0 && (s->regs[R_MDIO] & MDIO_CLK)) {
         /* shift data in */
         int bit = ((s->regs[R_MDIO] & MDIO_DO)
                    && (s->regs[R_MDIO] & MDIO_OE)) ? 1 : 0;
         m->data = (m->data << 1) | bit;

         /* check for sync */
         if (m->data == 0xffffffff) {
             m->count = 32;
         }

         if (m->count == 16) {
             uint8_t start = (m->data >> 14) & 0x3;
             uint8_t op = (m->data >> 12) & 0x3;
             uint8_t ta = (m->data) & 0x3;

             if (start == 1 && op == MDIO_OP_WRITE && ta == 2) {
                 m->state = MDIO_STATE_WRITING;
             } else if (start == 1 && op == MDIO_OP_READ && (ta & 1) == 0) {
                 m->state = MDIO_STATE_READING;
             } else {
                 m->state = MDIO_STATE_IDLE;
             }

             if (m->state != MDIO_STATE_IDLE) {
                 m->phy_addr = (m->data >> 7) & 0x1f;
                 m->reg_addr = (m->data >> 2) & 0x1f;
             }

             if (m->state == MDIO_STATE_READING) {
                 m->data_out = minimac_mdio_read_reg(s, m->phy_addr,
                         m->reg_addr);
             }
         }

         if (m->count < 16 && m->state == MDIO_STATE_READING) {
             int bit = (m->data_out & 0x8000) ? 1 : 0;
             m->data_out <<= 1;

             if (bit) {
                 s->regs[R_MDIO] |= MDIO_DI;
             } else {
                 s->regs[R_MDIO] &= ~MDIO_DI;
             }
         }

         if (m->count == 0 && m->state) {
             if (m->state == MDIO_STATE_WRITING) {
                 uint16_t data = m->data & 0xffff;
                 minimac_mdio_write_reg(s, m->phy_addr, m->reg_addr, data);
             }
             m->state = MDIO_STATE_IDLE;
         }
         m->count--;
     }

     m->last_clk = (s->regs[R_MDIO] & MDIO_CLK) ? 1 : 0;
 }

 static size_t assemble_frame(uint8_t *buf, size_t size,
         const uint8_t *payload, size_t payload_size)
 {
     uint32_t crc;

     if (size < payload_size + 12) {
         error_report("milkymist_minimac: received too big ethernet frame");
         return 0;
     }

     /* prepend preamble and sfd */
     memcpy(buf, preamble_sfd, 8);

     /* now copy the payload */
     memcpy(buf + 8, payload, payload_size);

     /* pad frame if needed */
     if (payload_size < 60) {
         memset(buf + payload_size + 8, 0, 60 - payload_size);
         payload_size = 60;
     }

     /* append fcs */
     crc = cpu_to_le32(crc32(0, buf + 8, payload_size));
     memcpy(buf + payload_size + 8, &crc, 4);

     return payload_size + 12;
 }

 static void minimac_tx(MilkymistMinimacState *s)
 {
     uint8_t buf[MINIMAC_MTU];
     uint32_t txcount = s->regs[R_TXCOUNT];

     /* do nothing if transmission logic is in reset */
     if (s->regs[R_SETUP] & SETUP_TX_RST) {
         return;
     }

     if (txcount < 64) {
         error_report("milkymist_minimac: ethernet frame too small (%u < %u)\n",
                 txcount, 64);
         return;
     }

     if (txcount > MINIMAC_MTU) {
         error_report("milkymist_minimac: MTU exceeded (%u > %u)\n",
                 txcount, MINIMAC_MTU);
         return;
     }

     /* dma */
     cpu_physical_memory_read(s->regs[R_TXADDR], buf, txcount);

     if (memcmp(buf, preamble_sfd, 8) != 0) {
         error_report("milkymist_minimac: frame doesn't contain the preamble "
                 "and/or the SFD (%02x %02x %02x %02x %02x %02x %02x %02x)\n",
                 buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
         return;
     }

     trace_milkymist_minimac_tx_frame(txcount - 12);

     /* send packet, skipping preamble and sfd */
     qemu_send_packet_raw(&s->nic->nc, buf + 8, txcount - 12);

     s->regs[R_TXCOUNT] = 0;

     trace_milkymist_minimac_pulse_irq_tx();
     qemu_irq_pulse(s->tx_irq);
 }

 static ssize_t minimac_rx(VLANClientState *nc, const uint8_t *buf, size_t size)
 {
     MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

     uint32_t r_addr;
     uint32_t r_count;
     uint32_t r_state;

     uint8_t frame_buf[MINIMAC_MTU];
     size_t frame_size;

     trace_milkymist_minimac_rx_frame(buf, size);

     /* discard frames if nic is in reset */
     if (s->regs[R_SETUP] & SETUP_RX_RST) {
         return size;
     }

     /* choose appropriate slot */
     if (s->regs[R_STATE0] == STATE_LOADED) {
         r_addr = R_ADDR0;
         r_count = R_COUNT0;
         r_state = R_STATE0;
     } else if (s->regs[R_STATE1] == STATE_LOADED) {
         r_addr = R_ADDR1;
         r_count = R_COUNT1;
         r_state = R_STATE1;
     } else if (s->regs[R_STATE2] == STATE_LOADED) {
         r_addr = R_ADDR2;
         r_count = R_COUNT2;
         r_state = R_STATE2;
     } else if (s->regs[R_STATE3] == STATE_LOADED) {
         r_addr = R_ADDR3;
         r_count = R_COUNT3;
         r_state = R_STATE3;
     } else {
         trace_milkymist_minimac_drop_rx_frame(buf);
         return size;
     }

     /* assemble frame */
     frame_size = assemble_frame(frame_buf, sizeof(frame_buf), buf, size);

     if (frame_size == 0) {
         return size;
     }

     trace_milkymist_minimac_rx_transfer(buf, frame_size);

     /* do dma */
     cpu_physical_memory_write(s->regs[r_addr], frame_buf, frame_size);

     /* update slot */
     s->regs[r_count] = frame_size;
     s->regs[r_state] = STATE_PENDING;

     trace_milkymist_minimac_pulse_irq_rx();
     qemu_irq_pulse(s->rx_irq);

     return size;
 }

 static uint32_t
 minimac_read(void *opaque, target_phys_addr_t addr)
 {
     MilkymistMinimacState *s = opaque;
     uint32_t r = 0;

     addr >>= 2;
     switch (addr) {
     case R_SETUP:
     case R_MDIO:
     case R_STATE0:
     case R_ADDR0:
     case R_COUNT0:
     case R_STATE1:
     case R_ADDR1:
     case R_COUNT1:
     case R_STATE2:
     case R_ADDR2:
     case R_COUNT2:
     case R_STATE3:
     case R_ADDR3:
     case R_COUNT3:
     case R_TXADDR:
     case R_TXCOUNT:
         r = s->regs[addr];
         break;

     default:
         error_report("milkymist_minimac: read access to unknown register 0x"
                 TARGET_FMT_plx, addr << 2);
         break;
     }

     trace_milkymist_minimac_memory_read(addr << 2, r);

     return r;
 }

 static void
 minimac_write(void *opaque, target_phys_addr_t addr, uint32_t value)
 {
     MilkymistMinimacState *s = opaque;

     trace_milkymist_minimac_memory_read(addr, value);

     addr >>= 2;
     switch (addr) {
     case R_MDIO:
     {
         /* MDIO_DI is read only */
         int mdio_di = (s->regs[R_MDIO] & MDIO_DI);
         s->regs[R_MDIO] = value;
         if (mdio_di) {
             s->regs[R_MDIO] |= mdio_di;
         } else {
             s->regs[R_MDIO] &= ~mdio_di;
         }

         minimac_update_mdio(s);
     } break;
     case R_TXCOUNT:
         s->regs[addr] = value;
         if (value > 0) {
             minimac_tx(s);
         }
         break;
     case R_SETUP:
     case R_STATE0:
     case R_ADDR0:
     case R_COUNT0:
     case R_STATE1:
     case R_ADDR1:
     case R_COUNT1:
     case R_STATE2:
     case R_ADDR2:
     case R_COUNT2:
     case R_STATE3:
     case R_ADDR3:
     case R_COUNT3:
     case R_TXADDR:
         s->regs[addr] = value;
         break;

     default:
         error_report("milkymist_minimac: write access to unknown register 0x"
                 TARGET_FMT_plx, addr << 2);
         break;
     }
 }

 static CPUReadMemoryFunc * const minimac_read_fn[] = {
     NULL,
     NULL,
     &minimac_read,
 };

 static CPUWriteMemoryFunc * const minimac_write_fn[] = {
     NULL,
     NULL,
     &minimac_write,
 };

 static int minimac_can_rx(VLANClientState *nc)
 {
     MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

     /* discard frames if nic is in reset */
     if (s->regs[R_SETUP] & SETUP_RX_RST) {
         return 1;
     }

     if (s->regs[R_STATE0] == STATE_LOADED) {
         return 1;
     }
     if (s->regs[R_STATE1] == STATE_LOADED) {
         return 1;
     }
     if (s->regs[R_STATE2] == STATE_LOADED) {
         return 1;
     }
     if (s->regs[R_STATE3] == STATE_LOADED) {
         return 1;
     }

     return 0;
 }

 static void minimac_cleanup(VLANClientState *nc)
 {
     MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

     s->nic = NULL;
 }

 static void milkymist_minimac_reset(DeviceState *d)
 {
     MilkymistMinimacState *s =
             container_of(d, MilkymistMinimacState, busdev.qdev);
     int i;

     for (i = 0; i < R_MAX; i++) {
         s->regs[i] = 0;
     }
     for (i = 0; i < R_PHY_MAX; i++) {
         s->phy_regs[i] = 0;
     }

     /* defaults */
     s->phy_regs[R_PHY_ID1] = 0x0022; /* Micrel KSZ8001L */
     s->phy_regs[R_PHY_ID2] = 0x161a;
 }

 static NetClientInfo net_milkymist_minimac_info = {
     .type = NET_CLIENT_TYPE_NIC,
     .size = sizeof(NICState),
     .can_receive = minimac_can_rx,
     .receive = minimac_rx,
     .cleanup = minimac_cleanup,
 };

 static int milkymist_minimac_init(SysBusDevice *dev)
 {
     MilkymistMinimacState *s = FROM_SYSBUS(typeof(*s), dev);
     int regs;

     sysbus_init_irq(dev, &s->rx_irq);
     sysbus_init_irq(dev, &s->tx_irq);

     regs = cpu_register_io_memory(minimac_read_fn, minimac_write_fn, s,
             DEVICE_NATIVE_ENDIAN);
     sysbus_init_mmio(dev, R_MAX * 4, regs);

     qemu_macaddr_default_if_unset(&s->conf.macaddr);
     s->nic = qemu_new_nic(&net_milkymist_minimac_info, &s->conf,
                           dev->qdev.info->name, dev->qdev.id, s);
     qemu_format_nic_info_str(&s->nic->nc, s->conf.macaddr.a);

     return 0;
 }

 static const VMStateDescription vmstate_milkymist_minimac_mdio = {
     .name = "milkymist_minimac_mdio",
     .version_id = 1,
     .minimum_version_id = 1,
     .minimum_version_id_old = 1,
     .fields      = (VMStateField[]) {
         VMSTATE_INT32(last_clk, MilkymistMinimacMdioState),
         VMSTATE_INT32(count, MilkymistMinimacMdioState),
         VMSTATE_UINT32(data, MilkymistMinimacMdioState),
         VMSTATE_UINT16(data_out, MilkymistMinimacMdioState),
         VMSTATE_INT32(state, MilkymistMinimacMdioState),
         VMSTATE_UINT8(phy_addr, MilkymistMinimacMdioState),
         VMSTATE_UINT8(reg_addr, MilkymistMinimacMdioState),
         VMSTATE_END_OF_LIST()
     }
 };

 static const VMStateDescription vmstate_milkymist_minimac = {
     .name = "milkymist-minimac",
     .version_id = 1,
     .minimum_version_id = 1,
     .minimum_version_id_old = 1,
     .fields      = (VMStateField[]) {
         VMSTATE_UINT32_ARRAY(regs, MilkymistMinimacState, R_MAX),
         VMSTATE_UINT16_ARRAY(phy_regs, MilkymistMinimacState, R_PHY_MAX),
         VMSTATE_STRUCT(mdio, MilkymistMinimacState, 0,
                 vmstate_milkymist_minimac_mdio, MilkymistMinimacMdioState),
         VMSTATE_END_OF_LIST()
     }
 };

 static SysBusDeviceInfo milkymist_minimac_info = {
     .init = milkymist_minimac_init,
     .qdev.name  = "milkymist-minimac",
     .qdev.size  = sizeof(MilkymistMinimacState),
     .qdev.vmsd  = &vmstate_milkymist_minimac,
     .qdev.reset = milkymist_minimac_reset,
     .qdev.props = (Property[]) {
         DEFINE_NIC_PROPERTIES(MilkymistMinimacState, conf),
         DEFINE_PROP_STRING("phy_model", MilkymistMinimacState, phy_model),
         DEFINE_PROP_END_OF_LIST(),
     }
 };

 static void milkymist_minimac_register(void)
 {
     sysbus_register_withprop(&milkymist_minimac_info);
 }

 device_init(milkymist_minimac_register)
	/*
	* QEMU model of the Milkymist minimac block.
	*
	* Copyright (c) 2010 Michael Walle <michael@walle.cc>
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this library; if not, see <http://www.gnu.org/licenses/>.
	*
	*
	* Specification available at:
	* http://www.milkymist.org/socdoc/minimac.pdf
	*
	*/

	#include "hw.h"
	#include "sysbus.h"
	#include "trace.h"
	#include "net.h"
	#include "qemu-error.h"

	#include <zlib.h>

	enum {
	R_SETUP = 0,
	R_MDIO,
	R_STATE0,
	R_ADDR0,
	R_COUNT0,
	R_STATE1,
	R_ADDR1,
	R_COUNT1,
	R_STATE2,
	R_ADDR2,
	R_COUNT2,
	R_STATE3,
	R_ADDR3,
	R_COUNT3,
	R_TXADDR,
	R_TXCOUNT,
	R_MAX
	};

	enum {
	SETUP_RX_RST = (1<<0),
	SETUP_TX_RST = (1<<2),
	};

	enum {
	MDIO_DO = (1<<0),
	MDIO_DI = (1<<1),
	MDIO_OE = (1<<2),
	MDIO_CLK = (1<<3),
	};

	enum {
	STATE_EMPTY = 0,
	STATE_LOADED = 1,
	STATE_PENDING = 2,
	};

	enum {
	MDIO_OP_WRITE = 1,
	MDIO_OP_READ = 2,
	};

	enum mdio_state {
	MDIO_STATE_IDLE,
	MDIO_STATE_READING,
	MDIO_STATE_WRITING,
	};

	enum {
	R_PHY_ID1 = 2,
	R_PHY_ID2 = 3,
	R_PHY_MAX = 32
	};

	#define MINIMAC_MTU 1530

	struct MilkymistMinimacMdioState {
	int last_clk;
	int count;
	uint32_t data;
	uint16_t data_out;
	int state;

	uint8_t phy_addr;
	uint8_t reg_addr;
	};
	typedef struct MilkymistMinimacMdioState MilkymistMinimacMdioState;

	struct MilkymistMinimacState {
	SysBusDevice busdev;
	NICState *nic;
	NICConf conf;
	char *phy_model;

	qemu_irq rx_irq;
	qemu_irq tx_irq;

	uint32_t regs[R_MAX];

	MilkymistMinimacMdioState mdio;

	uint16_t phy_regs[R_PHY_MAX];
	};
	typedef struct MilkymistMinimacState MilkymistMinimacState;

	static const uint8_t preamble_sfd[] = {
	0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xd5
	};

	static void minimac_mdio_write_reg(MilkymistMinimacState *s,
	uint8_t phy_addr, uint8_t reg_addr, uint16_t value)
	{
	trace_milkymist_minimac_mdio_write(phy_addr, reg_addr, value);

	/* nop */
	}

	static uint16_t minimac_mdio_read_reg(MilkymistMinimacState *s,
	uint8_t phy_addr, uint8_t reg_addr)
	{
	uint16_t r = s->phy_regs[reg_addr];

	trace_milkymist_minimac_mdio_read(phy_addr, reg_addr, r);

	return r;
	}

	static void minimac_update_mdio(MilkymistMinimacState *s)
	{
	MilkymistMinimacMdioState *m = &s->mdio;

	/* detect rising clk edge */
	if (m->last_clk == 0 && (s->regs[R_MDIO] & MDIO_CLK)) {
	/* shift data in */
	int bit = ((s->regs[R_MDIO] & MDIO_DO)
	&& (s->regs[R_MDIO] & MDIO_OE)) ? 1 : 0;
	m->data = (m->data << 1) \| bit;

	/* check for sync */
	if (m->data == 0xffffffff) {
	m->count = 32;
	}

	if (m->count == 16) {
	uint8_t start = (m->data >> 14) & 0x3;
	uint8_t op = (m->data >> 12) & 0x3;
	uint8_t ta = (m->data) & 0x3;

	if (start == 1 && op == MDIO_OP_WRITE && ta == 2) {
	m->state = MDIO_STATE_WRITING;
	} else if (start == 1 && op == MDIO_OP_READ && (ta & 1) == 0) {
	m->state = MDIO_STATE_READING;
	} else {
	m->state = MDIO_STATE_IDLE;
	}

	if (m->state != MDIO_STATE_IDLE) {
	m->phy_addr = (m->data >> 7) & 0x1f;
	m->reg_addr = (m->data >> 2) & 0x1f;
	}

	if (m->state == MDIO_STATE_READING) {
	m->data_out = minimac_mdio_read_reg(s, m->phy_addr,
	m->reg_addr);
	}
	}

	if (m->count < 16 && m->state == MDIO_STATE_READING) {
	int bit = (m->data_out & 0x8000) ? 1 : 0;
	m->data_out <<= 1;

	if (bit) {
	s->regs[R_MDIO] \|= MDIO_DI;
	} else {
	s->regs[R_MDIO] &= ~MDIO_DI;
	}
	}

	if (m->count == 0 && m->state) {
	if (m->state == MDIO_STATE_WRITING) {
	uint16_t data = m->data & 0xffff;
	minimac_mdio_write_reg(s, m->phy_addr, m->reg_addr, data);
	}
	m->state = MDIO_STATE_IDLE;
	}
	m->count--;
	}

	m->last_clk = (s->regs[R_MDIO] & MDIO_CLK) ? 1 : 0;
	}

	static size_t assemble_frame(uint8_t *buf, size_t size,
	const uint8_t *payload, size_t payload_size)
	{
	uint32_t crc;

	if (size < payload_size + 12) {
	error_report("milkymist_minimac: received too big ethernet frame");
	return 0;
	}

	/* prepend preamble and sfd */
	memcpy(buf, preamble_sfd, 8);

	/* now copy the payload */
	memcpy(buf + 8, payload, payload_size);

	/* pad frame if needed */
	if (payload_size < 60) {
	memset(buf + payload_size + 8, 0, 60 - payload_size);
	payload_size = 60;
	}

	/* append fcs */
	crc = cpu_to_le32(crc32(0, buf + 8, payload_size));
	memcpy(buf + payload_size + 8, &crc, 4);

	return payload_size + 12;
	}

	static void minimac_tx(MilkymistMinimacState *s)
	{
	uint8_t buf[MINIMAC_MTU];
	uint32_t txcount = s->regs[R_TXCOUNT];

	/* do nothing if transmission logic is in reset */
	if (s->regs[R_SETUP] & SETUP_TX_RST) {
	return;
	}

	if (txcount < 64) {
	error_report("milkymist_minimac: ethernet frame too small (%u < %u)\n",
	txcount, 64);
	return;
	}

	if (txcount > MINIMAC_MTU) {
	error_report("milkymist_minimac: MTU exceeded (%u > %u)\n",
	txcount, MINIMAC_MTU);
	return;
	}

	/* dma */
	cpu_physical_memory_read(s->regs[R_TXADDR], buf, txcount);

	if (memcmp(buf, preamble_sfd, 8) != 0) {
	error_report("milkymist_minimac: frame doesn't contain the preamble "
	"and/or the SFD (%02x %02x %02x %02x %02x %02x %02x %02x)\n",
	buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
	return;
	}

	trace_milkymist_minimac_tx_frame(txcount - 12);

	/* send packet, skipping preamble and sfd */
	qemu_send_packet_raw(&s->nic->nc, buf + 8, txcount - 12);

	s->regs[R_TXCOUNT] = 0;

	trace_milkymist_minimac_pulse_irq_tx();
	qemu_irq_pulse(s->tx_irq);
	}

	static ssize_t minimac_rx(VLANClientState nc, const uint8_t buf, size_t size)
	{
	MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

	uint32_t r_addr;
	uint32_t r_count;
	uint32_t r_state;

	uint8_t frame_buf[MINIMAC_MTU];
	size_t frame_size;

	trace_milkymist_minimac_rx_frame(buf, size);

	/* discard frames if nic is in reset */
	if (s->regs[R_SETUP] & SETUP_RX_RST) {
	return size;
	}

	/* choose appropriate slot */
	if (s->regs[R_STATE0] == STATE_LOADED) {
	r_addr = R_ADDR0;
	r_count = R_COUNT0;
	r_state = R_STATE0;
	} else if (s->regs[R_STATE1] == STATE_LOADED) {
	r_addr = R_ADDR1;
	r_count = R_COUNT1;
	r_state = R_STATE1;
	} else if (s->regs[R_STATE2] == STATE_LOADED) {
	r_addr = R_ADDR2;
	r_count = R_COUNT2;
	r_state = R_STATE2;
	} else if (s->regs[R_STATE3] == STATE_LOADED) {
	r_addr = R_ADDR3;
	r_count = R_COUNT3;
	r_state = R_STATE3;
	} else {
	trace_milkymist_minimac_drop_rx_frame(buf);
	return size;
	}

	/* assemble frame */
	frame_size = assemble_frame(frame_buf, sizeof(frame_buf), buf, size);

	if (frame_size == 0) {
	return size;
	}

	trace_milkymist_minimac_rx_transfer(buf, frame_size);

	/* do dma */
	cpu_physical_memory_write(s->regs[r_addr], frame_buf, frame_size);

	/* update slot */
	s->regs[r_count] = frame_size;
	s->regs[r_state] = STATE_PENDING;

	trace_milkymist_minimac_pulse_irq_rx();
	qemu_irq_pulse(s->rx_irq);

	return size;
	}

	static uint32_t
	minimac_read(void *opaque, target_phys_addr_t addr)
	{
	MilkymistMinimacState *s = opaque;
	uint32_t r = 0;

	addr >>= 2;
	switch (addr) {
	case R_SETUP:
	case R_MDIO:
	case R_STATE0:
	case R_ADDR0:
	case R_COUNT0:
	case R_STATE1:
	case R_ADDR1:
	case R_COUNT1:
	case R_STATE2:
	case R_ADDR2:
	case R_COUNT2:
	case R_STATE3:
	case R_ADDR3:
	case R_COUNT3:
	case R_TXADDR:
	case R_TXCOUNT:
	r = s->regs[addr];
	break;

	default:
	error_report("milkymist_minimac: read access to unknown register 0x"
	TARGET_FMT_plx, addr << 2);
	break;
	}

	trace_milkymist_minimac_memory_read(addr << 2, r);

	return r;
	}

	static void
	minimac_write(void *opaque, target_phys_addr_t addr, uint32_t value)
	{
	MilkymistMinimacState *s = opaque;

	trace_milkymist_minimac_memory_read(addr, value);

	addr >>= 2;
	switch (addr) {
	case R_MDIO:
	{
	/* MDIO_DI is read only */
	int mdio_di = (s->regs[R_MDIO] & MDIO_DI);
	s->regs[R_MDIO] = value;
	if (mdio_di) {
	s->regs[R_MDIO] \|= mdio_di;
	} else {
	s->regs[R_MDIO] &= ~mdio_di;
	}

	minimac_update_mdio(s);
	} break;
	case R_TXCOUNT:
	s->regs[addr] = value;
	if (value > 0) {
	minimac_tx(s);
	}
	break;
	case R_SETUP:
	case R_STATE0:
	case R_ADDR0:
	case R_COUNT0:
	case R_STATE1:
	case R_ADDR1:
	case R_COUNT1:
	case R_STATE2:
	case R_ADDR2:
	case R_COUNT2:
	case R_STATE3:
	case R_ADDR3:
	case R_COUNT3:
	case R_TXADDR:
	s->regs[addr] = value;
	break;

	default:
	error_report("milkymist_minimac: write access to unknown register 0x"
	TARGET_FMT_plx, addr << 2);
	break;
	}
	}

	static CPUReadMemoryFunc * const minimac_read_fn[] = {
	NULL,
	NULL,
	&minimac_read,
	};

	static CPUWriteMemoryFunc * const minimac_write_fn[] = {
	NULL,
	NULL,
	&minimac_write,
	};

	static int minimac_can_rx(VLANClientState *nc)
	{
	MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

	/* discard frames if nic is in reset */
	if (s->regs[R_SETUP] & SETUP_RX_RST) {
	return 1;
	}

	if (s->regs[R_STATE0] == STATE_LOADED) {
	return 1;
	}
	if (s->regs[R_STATE1] == STATE_LOADED) {
	return 1;
	}
	if (s->regs[R_STATE2] == STATE_LOADED) {
	return 1;
	}
	if (s->regs[R_STATE3] == STATE_LOADED) {
	return 1;
	}

	return 0;
	}

	static void minimac_cleanup(VLANClientState *nc)
	{
	MilkymistMinimacState *s = DO_UPCAST(NICState, nc, nc)->opaque;

	s->nic = NULL;
	}

	static void milkymist_minimac_reset(DeviceState *d)
	{
	MilkymistMinimacState *s =
	container_of(d, MilkymistMinimacState, busdev.qdev);
	int i;

	for (i = 0; i < R_MAX; i++) {
	s->regs[i] = 0;
	}
	for (i = 0; i < R_PHY_MAX; i++) {
	s->phy_regs[i] = 0;
	}

	/* defaults */
	s->phy_regs[R_PHY_ID1] = 0x0022; /* Micrel KSZ8001L */
	s->phy_regs[R_PHY_ID2] = 0x161a;
	}

	static NetClientInfo net_milkymist_minimac_info = {
	.type = NET_CLIENT_TYPE_NIC,
	.size = sizeof(NICState),
	.can_receive = minimac_can_rx,
	.receive = minimac_rx,
	.cleanup = minimac_cleanup,
	};

	static int milkymist_minimac_init(SysBusDevice *dev)
	{
	MilkymistMinimacState s = FROM_SYSBUS(typeof(s), dev);
	int regs;

	sysbus_init_irq(dev, &s->rx_irq);
	sysbus_init_irq(dev, &s->tx_irq);

	regs = cpu_register_io_memory(minimac_read_fn, minimac_write_fn, s,
	DEVICE_NATIVE_ENDIAN);
	sysbus_init_mmio(dev, R_MAX * 4, regs);

	qemu_macaddr_default_if_unset(&s->conf.macaddr);
	s->nic = qemu_new_nic(&net_milkymist_minimac_info, &s->conf,
	dev->qdev.info->name, dev->qdev.id, s);
	qemu_format_nic_info_str(&s->nic->nc, s->conf.macaddr.a);

	return 0;
	}

	static const VMStateDescription vmstate_milkymist_minimac_mdio = {
	.name = "milkymist_minimac_mdio",
	.version_id = 1,
	.minimum_version_id = 1,
	.minimum_version_id_old = 1,
	.fields = (VMStateField[]) {
	VMSTATE_INT32(last_clk, MilkymistMinimacMdioState),
	VMSTATE_INT32(count, MilkymistMinimacMdioState),
	VMSTATE_UINT32(data, MilkymistMinimacMdioState),
	VMSTATE_UINT16(data_out, MilkymistMinimacMdioState),
	VMSTATE_INT32(state, MilkymistMinimacMdioState),
	VMSTATE_UINT8(phy_addr, MilkymistMinimacMdioState),
	VMSTATE_UINT8(reg_addr, MilkymistMinimacMdioState),
	VMSTATE_END_OF_LIST()
	}
	};

	static const VMStateDescription vmstate_milkymist_minimac = {
	.name = "milkymist-minimac",
	.version_id = 1,
	.minimum_version_id = 1,
	.minimum_version_id_old = 1,
	.fields = (VMStateField[]) {
	VMSTATE_UINT32_ARRAY(regs, MilkymistMinimacState, R_MAX),
	VMSTATE_UINT16_ARRAY(phy_regs, MilkymistMinimacState, R_PHY_MAX),
	VMSTATE_STRUCT(mdio, MilkymistMinimacState, 0,
	vmstate_milkymist_minimac_mdio, MilkymistMinimacMdioState),
	VMSTATE_END_OF_LIST()
	}
	};

	static SysBusDeviceInfo milkymist_minimac_info = {
	.init = milkymist_minimac_init,
	.qdev.name = "milkymist-minimac",
	.qdev.size = sizeof(MilkymistMinimacState),
	.qdev.vmsd = &vmstate_milkymist_minimac,
	.qdev.reset = milkymist_minimac_reset,
	.qdev.props = (Property[]) {
	DEFINE_NIC_PROPERTIES(MilkymistMinimacState, conf),
	DEFINE_PROP_STRING("phy_model", MilkymistMinimacState, phy_model),
	DEFINE_PROP_END_OF_LIST(),
	}
	};

	static void milkymist_minimac_register(void)
	{
	sysbus_register_withprop(&milkymist_minimac_info);
	}

	device_init(milkymist_minimac_register)