Re: [Qemu devel PATCH v4 1/3] hw/net: Add Smartfusion2 emac block

[Philippe Mathieu-Daudé]

Hi Sundeep,

On 4/10/20 4:45 PM, address@hidden wrote:
> From: Subbaraya Sundeep <address@hidden>
> 
> Modelled Ethernet MAC of Smartfusion2 SoC.
> Micrel KSZ8051 PHY is present on Emcraft's
> SOM kit hence same PHY is emulated.
> 
> Signed-off-by: Subbaraya Sundeep <address@hidden>
> ---
>  MAINTAINERS                |   2 +
>  hw/net/Makefile.objs       |   1 +
>  hw/net/msf2-emac.c         | 562 
> +++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/net/msf2-emac.h |  50 ++++
>  4 files changed, 615 insertions(+)
>  create mode 100644 hw/net/msf2-emac.c
>  create mode 100644 include/hw/net/msf2-emac.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 642c8e0..9d0ff20 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -919,6 +919,8 @@ F: include/hw/arm/msf2-soc.h
>  F: include/hw/misc/msf2-sysreg.h
>  F: include/hw/timer/mss-timer.h
>  F: include/hw/ssi/mss-spi.h
> +F: hw/net/msf2-emac.c
> +F: include/hw/net/msf2-emac.h
>  
>  Emcraft M2S-FG484
>  M: Subbaraya Sundeep <address@hidden>
> diff --git a/hw/net/Makefile.objs b/hw/net/Makefile.objs
> index af4d194..f2b7398 100644
> --- a/hw/net/Makefile.objs
> +++ b/hw/net/Makefile.objs
> @@ -55,3 +55,4 @@ common-obj-$(CONFIG_ROCKER) += rocker/rocker.o 
> rocker/rocker_fp.o \
>  obj-$(call lnot,$(CONFIG_ROCKER)) += rocker/qmp-norocker.o
>  
>  common-obj-$(CONFIG_CAN_BUS) += can/
> +common-obj-$(CONFIG_MSF2) += msf2-emac.o
> diff --git a/hw/net/msf2-emac.c b/hw/net/msf2-emac.c
> new file mode 100644
> index 0000000..78593f4
> --- /dev/null
> +++ b/hw/net/msf2-emac.c
> @@ -0,0 +1,562 @@
> +/*
> + * QEMU model of the Smartfusion2 Ethernet MAC.
> + *
> + * Copyright (c) 2020 Subbaraya Sundeep <address@hidden>.
> + *
> + * 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.
> + *
> + * Refer to section Ethernet MAC in the document:
> + * UG0331: SmartFusion2 Microcontroller Subsystem User Guide
> + * Datasheet URL:
> + * 
> https://www.microsemi.com/document-portal/cat_view/56661-internal-documents/
> + * 56758-soc?lang=en&limit=20&limitstart=220
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu-common.h"
> +#include "qemu/log.h"
> +#include "exec/address-spaces.h"
> +#include "hw/registerfields.h"
> +#include "hw/net/msf2-emac.h"
> +#include "hw/net/mii.h"
> +#include "hw/irq.h"
> +#include "net/net.h"
> +#include "hw/qdev-properties.h"
> +#include "migration/vmstate.h"
> +
> +REG32(CFG1, 0x0)
> +REG32(CFG2, 0x4)
> +REG32(IFG, 0x8)
> +REG32(HALF_DUPLEX, 0xc)
> +REG32(FRM_LEN, 0x10)

MAX_FRAME_LENGTH, OK.

> +REG32(MII_CMD, 0x24)
> +REG32(MII_ADDR, 0x28)
> +REG32(MII_CTL, 0x2c)
> +REG32(MII_STS, 0x30)
> +REG32(STA1, 0x40)
> +REG32(STA2, 0x44)
> +REG32(FIFO_CFG0, 0x48)

> +REG32(DMA_TX_CTL, 0x180)
> +REG32(DMA_TX_DESC, 0x184)
> +REG32(DMA_TX_STATUS, 0x188)
> +REG32(DMA_RX_CTL, 0x18c)
> +REG32(DMA_RX_DESC, 0x190)
> +REG32(DMA_RX_STATUS, 0x194)
> +REG32(DMA_IRQ_MASK, 0x198)
> +REG32(DMA_IRQ, 0x19c)

OK.

> +
> +FIELD(DMA, PKTCNT, 16, 8)

For both RX/TX, OK.

> +
> +#define R_DMA_PKT_TXRX          (1 << 0)
> +#define DMA_TX_UNDERRUN         (1 << 1)
> +#define DMA_RX_OVERFLOW         (1 << 2)
> +
> +#define EMPTY_MASK              (1 << 31)
> +#define PKT_SIZE                0x7FF
> +
> +#define CFG1_RESET              (1 << 31)
> +#define CFG1_RX_EN              (1 << 2)
> +#define CFG1_TX_EN              (1 << 0)
> +#define CFG1_LB_EN              (1 << 8)
> +
> +#define DMA_TX_CTL_EN           (1 << 0)
> +#define DMA_RX_CTL_EN           (1 << 0)
> +
> +#define MII_CMD_READ            (1 << 0)

You previously used the FIELD() API, then switched to classical
#define... Odd.

> +
> +#define PHYADDR                 0x1
> +#define MII_ADDR_MASK           0x1F
> +#define PHY_ADDR_SHIFT          8
> +#define MAX_PKT_SIZE            2048
> +
> +typedef struct {
> +    uint32_t pktaddr;
> +    uint32_t pktsize;
> +    uint32_t next;
> +} EmacDesc;
> +
> +static uint32_t emac_get_isr(MSF2EmacState *s)
> +{
> +    uint32_t ier = s->regs[R_DMA_IRQ_MASK];
> +    uint32_t tx = s->regs[R_DMA_TX_STATUS] & 0xF;
> +    uint32_t rx = s->regs[R_DMA_RX_STATUS] & 0xF;
> +    uint32_t isr = (rx << 4) | tx;
> +
> +    s->regs[R_DMA_IRQ] = ier & isr;
> +    return s->regs[R_DMA_IRQ];
> +}
> +
> +static void emac_update_irq(MSF2EmacState *s)
> +{
> +    bool intr = emac_get_isr(s);
> +
> +    qemu_set_irq(s->irq, intr);
> +}
> +
> +static void emac_load_desc(MSF2EmacState *s, EmacDesc *d, hwaddr desc)
> +{
> +    address_space_read(&s->dma_as, desc, MEMTXATTRS_UNSPECIFIED,
> +                       (uint8_t *)d, sizeof *d);

No need to cast to (uint8_t *).

> +    /* Convert from LE into host endianness. */
> +    d->pktaddr = le32_to_cpu(d->pktaddr);
> +    d->pktsize = le32_to_cpu(d->pktsize);
> +    d->next = le32_to_cpu(d->next);
> +}
> +
> +static void emac_store_desc(MSF2EmacState *s, EmacDesc *d, hwaddr desc)
> +{
> +    /* Convert from host endianness into LE. */
> +    d->pktaddr = cpu_to_le32(d->pktaddr);
> +    d->pktsize = cpu_to_le32(d->pktsize);
> +    d->next = cpu_to_le32(d->next);
> +
> +    address_space_write(&s->dma_as, desc, MEMTXATTRS_UNSPECIFIED,
> +                        (uint8_t *)d, sizeof *d);

No need to cast to (uint8_t *).

> +}
> +
> +static void msf2_dma_tx(MSF2EmacState *s)
> +{
> +    NetClientState *nc = qemu_get_queue(s->nic);
> +    hwaddr desc = s->regs[R_DMA_TX_DESC];
> +    uint8_t buf[MAX_PKT_SIZE];
> +    EmacDesc d;
> +    int size;
> +    uint8_t pktcnt;
> +    uint32_t status;
> +
> +    if (!(s->regs[R_CFG1] & CFG1_TX_EN)) {
> +        return;
> +    }
> +
> +    while (1) {
> +        emac_load_desc(s, &d, desc);
> +        if (d.pktsize & EMPTY_MASK) {
> +            break;
> +        }
> +        size = d.pktsize & PKT_SIZE;
> +        address_space_read(&s->dma_as, d.pktaddr, MEMTXATTRS_UNSPECIFIED,
> +                           buf, size);
> +        /*
> +         * This is very basic way to send packets. Ideally there should be
> +         * a FIFO and packets should be sent out from FIFO only when
> +         * R_CFG1 bit 0 is set.
> +         */
> +        if (s->regs[R_CFG1] & CFG1_LB_EN) {
> +            nc->info->receive(nc, buf, size);
> +        } else {
> +            qemu_send_packet(nc, buf, size);
> +        }
> +        d.pktsize |= EMPTY_MASK;
> +        emac_store_desc(s, &d, desc);
> +        /* update sent packets count */
> +        status = s->regs[R_DMA_TX_STATUS];
> +        pktcnt = extract32(status, R_DMA_PKTCNT_SHIFT, 8);

Declaring:

FIELD(DMA_RX_DESC, PKTCNT, 16, 8)

You can then use:

           pktcnt = FIELD_EX32(status, DMA_TX_STATUS, PKTCNT);

> +        pktcnt++;
> +        s->regs[R_DMA_TX_STATUS] = deposit32(status, R_DMA_PKTCNT_SHIFT,
> +                                             8, pktcnt);
> +        s->regs[R_DMA_TX_STATUS] |= R_DMA_PKT_TXRX;
> +        desc = d.next;
> +    }
> +    s->regs[R_DMA_TX_STATUS] |= DMA_TX_UNDERRUN;
> +    s->regs[R_DMA_TX_CTL] &= ~DMA_TX_CTL_EN;
> +}
> +
> +static void msf2_phy_update_link(MSF2EmacState *s)
> +{
> +    /* Autonegotiation status mirrors link status. */
> +    if (qemu_get_queue(s->nic)->link_down) {
> +        s->phy_regs[MII_BMSR] &= ~(MII_BMSR_AN_COMP |
> +                                         MII_BMSR_LINK_ST);

Indent off.

> +    } else {
> +        s->phy_regs[MII_BMSR] |= (MII_BMSR_AN_COMP |
> +                                         MII_BMSR_LINK_ST);

Ditto.

> +    }
> +}
> +
> +static void msf2_phy_reset(MSF2EmacState *s)
> +{
> +    memset(&s->phy_regs[0], 0, sizeof(s->phy_regs));
> +    s->phy_regs[MII_BMCR] = 0x1140;
> +    s->phy_regs[MII_BMSR] = 0x7968;
> +    s->phy_regs[MII_PHYID1] = 0x0022;
> +    s->phy_regs[MII_PHYID2] = 0x1550;
> +    s->phy_regs[MII_ANAR] = 0x01E1;
> +    s->phy_regs[MII_ANLPAR] = 0xCDE1;
> +
> +    msf2_phy_update_link(s);
> +}
> +
> +static void write_to_phy(MSF2EmacState *s)
> +{
> +    uint8_t reg_addr = s->regs[R_MII_ADDR] & MII_ADDR_MASK;
> +    uint8_t phy_addr = (s->regs[R_MII_ADDR] >> PHY_ADDR_SHIFT) & 
> MII_ADDR_MASK;
> +    uint16_t data = s->regs[R_MII_CTL] & 0xFFFF;
> +
> +    if (phy_addr != PHYADDR) {
> +        return;
> +    }
> +
> +    switch (reg_addr) {
> +    case MII_BMCR:
> +        if (data & MII_BMCR_RESET) {
> +            /* Phy reset */
> +            msf2_phy_reset(s);
> +            data &= ~MII_BMCR_RESET;
> +        }
> +        if (data & MII_BMCR_AUTOEN) {
> +            /* Complete autonegotiation immediately */
> +            data &= ~MII_BMCR_AUTOEN;
> +            s->phy_regs[MII_BMSR] |= MII_BMSR_AN_COMP;
> +        }
> +        break;
> +    }
> +
> +    s->phy_regs[reg_addr] = data;
> +}
> +
> +static uint16_t read_from_phy(MSF2EmacState *s)
> +{
> +    uint8_t reg_addr = s->regs[R_MII_ADDR] & MII_ADDR_MASK;
> +    uint8_t phy_addr = (s->regs[R_MII_ADDR] >> PHY_ADDR_SHIFT) & 
> MII_ADDR_MASK;
> +
> +    if (phy_addr == PHYADDR) {
> +        return s->phy_regs[reg_addr];
> +    } else {
> +        return 0xFFFF;
> +    }
> +}
> +
> +static void msf2_emac_do_reset(MSF2EmacState *s)
> +{
> +    memset(&s->regs[0], 0, sizeof(s->regs));
> +    s->regs[R_CFG1] = 0x80000000;
> +    s->regs[R_CFG2] = 0x00007000;
> +    s->regs[R_IFG] = 0x40605060;
> +    s->regs[R_HALF_DUPLEX] = 0x00A1F037;
> +    s->regs[R_FRM_LEN] = 0x00000600;

OK.

> +
> +    msf2_phy_reset(s);
> +}
> +
> +static uint64_t emac_read(void *opaque, hwaddr addr, unsigned int size)
> +{
> +    MSF2EmacState *s = opaque;
> +    uint32_t r = 0;
> +
> +    addr >>= 2;
> +
> +    switch (addr) {
> +    case R_DMA_IRQ:
> +        r = emac_get_isr(s);
> +        break;
> +    default:
> +        if (addr < ARRAY_SIZE(s->regs)) {
> +            r = s->regs[addr];
> +        } else {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                         "%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
> +                         addr * 4);
> +            return r;
> +        }

Easier to review inverting the if():

      if (addr >= ARRAY_SIZE(s->regs)) {
          qemu_log_mask(LOG_GUEST_ERROR,
                        "%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
                        addr * 4);
          return r;
      }
      r = s->regs[addr];

> +        break;
> +    }
> +    return r;
> +}
> +
> +static void emac_write(void *opaque, hwaddr addr, uint64_t val64,
> +        unsigned int size)
> +{
> +    MSF2EmacState *s = opaque;
> +    uint32_t value = val64;
> +    uint32_t enreqbits;
> +    uint8_t pktcnt;
> +
> +    addr >>= 2;
> +    switch (addr) {
> +    case R_DMA_TX_CTL:
> +        s->regs[addr] = value;
> +        if (value & DMA_TX_CTL_EN) {
> +            msf2_dma_tx(s);
> +        }
> +        break;
> +    case R_DMA_RX_CTL:
> +        s->regs[addr] = value;
> +        if (value & DMA_RX_CTL_EN) {
> +            s->rx_desc = s->regs[R_DMA_RX_DESC];
> +            qemu_flush_queued_packets(qemu_get_queue(s->nic));
> +        }
> +        break;
> +    case R_CFG1:
> +        if (value & CFG1_RESET) {
> +            msf2_emac_do_reset(s);
> +        }
> +    case R_FIFO_CFG0:
> +       /*
> +        * For our implementation, turning on modules is instantaneous,
> +        * so the states requested via the *ENREQ bits appear in the
> +        * *ENRPLY bits immediately. Also the reset bits to reset PE-MCXMAC
> +        * module are not emulated here since it deals with start of frames,
> +        * inter-packet gap and control frames.
> +        */
> +        enreqbits = extract32(value, 8, 5);
> +        value = deposit32(value, 16, 5, enreqbits);
> +        s->regs[addr] = value;

OK. Maybe directly:

           s->regs[addr] = deposit32(value, 16, 5, enreqbits);

> +        break;
> +    case R_DMA_TX_DESC:
> +        if (value & 0x3) {
> +            qemu_log_mask(LOG_GUEST_ERROR, "Tx Descriptor address should be"
> +                        " 32 bit aligned\n");
> +        }
> +        /* Ignore [1:0] bits */
> +        s->regs[addr] = value & 0xFFFFFFFC;

Simpler as 'value & ~3'.

> +        break;
> +    case R_DMA_RX_DESC:
> +        if (value & 0x3) {
> +            qemu_log_mask(LOG_GUEST_ERROR, "Rx Descriptor address should be"
> +                        " 32 bit aligned\n");
> +        }
> +        /* Ignore [1:0] bits */
> +        s->regs[addr] = value & 0xFFFFFFFC;
> +        break;
> +    case R_DMA_TX_STATUS:
> +        if (value & DMA_TX_UNDERRUN) {
> +            s->regs[addr] &= ~DMA_TX_UNDERRUN;
> +        }
> +        if (value & R_DMA_PKT_TXRX) {
> +            pktcnt = extract32(s->regs[addr], R_DMA_PKTCNT_SHIFT,
> +                               R_DMA_PKTCNT_LENGTH);
> +            pktcnt--;
> +            s->regs[addr] = deposit32(s->regs[addr], R_DMA_PKTCNT_SHIFT,
> +                                      8, pktcnt);
> +            if (pktcnt == 0) {
> +                s->regs[addr] &= ~R_DMA_PKT_TXRX;
> +            }
> +        }
> +        break;
> +    case R_DMA_RX_STATUS:
> +        if (value & DMA_RX_OVERFLOW) {
> +            s->regs[addr] &= ~DMA_RX_OVERFLOW;
> +        }
> +        if (value & R_DMA_PKT_TXRX) {
> +            pktcnt = extract32(s->regs[addr], R_DMA_PKTCNT_SHIFT,
> +                               R_DMA_PKTCNT_LENGTH);
> +            pktcnt--;
> +            s->regs[addr] = deposit32(s->regs[addr], R_DMA_PKTCNT_SHIFT,
> +                                      8, pktcnt);
> +            if (pktcnt == 0) {
> +                s->regs[addr] &= ~R_DMA_PKT_TXRX;
> +            }
> +        }
> +        break;
> +    case R_DMA_IRQ:
> +        break;
> +    case R_MII_CMD:
> +        if (value & MII_CMD_READ) {
> +            s->regs[R_MII_STS] = read_from_phy(s);
> +        }
> +        break;
> +    case R_MII_CTL:
> +        s->regs[addr] = value;
> +        write_to_phy(s);
> +        break;
> +    default:
> +        if (addr < ARRAY_SIZE(s->regs)) {
> +            s->regs[addr] = value;
> +        } else {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                         "%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
> +                         addr * 4);
> +            return;
> +        }
> +        break;
> +    }
> +    emac_update_irq(s);
> +}
> +
> +static const MemoryRegionOps emac_ops = {
> +    .read = emac_read,
> +    .write = emac_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +    .valid = {

You probably wanted to use .impl instead of .valid here,
your implementation is clearly 32-bit. The bus doesn't seem restricted
to 32-bit.

> +        .min_access_size = 4,
> +        .max_access_size = 4
> +    }
> +};
> +
> +static bool emac_can_rx(NetClientState *nc)
> +{
> +    MSF2EmacState *s = qemu_get_nic_opaque(nc);
> +
> +    return (s->regs[R_CFG1] & CFG1_RX_EN) &&
> +           (s->regs[R_DMA_RX_CTL] & DMA_RX_CTL_EN);
> +}
> +
> +static bool match_addr(MSF2EmacState *s, const uint8_t *buf)
> +{
> +    /* The broadcast MAC address: FF:FF:FF:FF:FF:FF */
> +    static const uint8_t broadcast_addr[] = { 0xFF, 0xFF, 0xFF, 0xFF,
> +                                              0xFF, 0xFF };
> +    uint8_t addr[6];
> +
> +    if (!memcmp(buf, broadcast_addr, sizeof(broadcast_addr))) {
> +        return true;
> +    }
> +
> +    /*
> +     * R_STA1 [31:24] : octet 1 of mac address
> +     * R_STA1 [23:16] : octet 2 of mac address
> +     *          .
> +     *          .
> +     * R_STA2 [31:24] : octet 5 of mac address
> +     * R_STA2 [23:16] : octet 6 of mac address
> +     */
> +    stl_le_p(addr, s->regs[R_STA1]);
> +    stw_le_p(addr + 4, s->regs[R_STA2] >> 16);

You probably want to do cache this in MSF2EmacState and only update when
R_STA1/R_STA2 are written. IOW, move uint8_t addr[6] to MSF2EmacState,
and here simply memcmp(s->station_address).

> +
> +    if (!memcmp(buf, addr, sizeof(addr))) {
> +        return false;
> +    }
> +
> +    return true;
> +}
> +
> +static ssize_t emac_rx(NetClientState *nc, const uint8_t *buf, size_t size)
> +{
> +    MSF2EmacState *s = qemu_get_nic_opaque(nc);
> +    EmacDesc d;
> +    uint8_t pktcnt;
> +    uint32_t status;
> +
> +    if (size > (s->regs[R_FRM_LEN] & 0xFFFF)) {
> +        return -1;

Hard to tell, since "net/net.h" is completely undocumented, but I'd
expect to return 'size' to avoid queueing the same packets over and
over. I'll let Jason review this part.

> +    }
> +    if (!match_addr(s, buf)) {
> +        return -1;

Ditto.

> +    }
> +
> +    emac_load_desc(s, &d, s->rx_desc);
> +
> +    if (d.pktsize & EMPTY_MASK) {
> +        address_space_write(&s->dma_as, d.pktaddr, MEMTXATTRS_UNSPECIFIED,
> +                            buf, size & PKT_SIZE);
> +        d.pktsize = size & PKT_SIZE;
> +        emac_store_desc(s, &d, s->rx_desc);
> +        /* update received packets count */
> +        status = s->regs[R_DMA_RX_STATUS];
> +        pktcnt = extract32(status, R_DMA_PKTCNT_SHIFT, 8);
> +        pktcnt++;
> +        s->regs[R_DMA_RX_STATUS] = deposit32(status, R_DMA_PKTCNT_SHIFT,
> +                                             8, pktcnt);
> +        s->regs[R_DMA_RX_STATUS] |= R_DMA_PKT_TXRX;
> +        s->rx_desc = d.next;
> +    } else {
> +        s->regs[R_DMA_RX_CTL] &= ~DMA_RX_CTL_EN;
> +        s->regs[R_DMA_RX_STATUS] |= DMA_RX_OVERFLOW;
> +    }
> +    emac_update_irq(s);
> +    return size;
> +}
> +
> +static void msf2_emac_reset(DeviceState *dev)
> +{
> +    MSF2EmacState *s = MSS_EMAC(dev);
> +
> +    msf2_emac_do_reset(s);
> +}
> +
> +static void emac_set_link(NetClientState *nc)
> +{
> +    MSF2EmacState *s = qemu_get_nic_opaque(nc);
> +
> +    msf2_phy_update_link(s);
> +}
> +
> +static NetClientInfo net_msf2_emac_info = {
> +    .type = NET_CLIENT_DRIVER_NIC,
> +    .size = sizeof(NICState),
> +    .can_receive = emac_can_rx,
> +    .receive = emac_rx,
> +    .link_status_changed = emac_set_link,
> +};
> +
> +static void msf2_emac_realize(DeviceState *dev, Error **errp)
> +{
> +    MSF2EmacState *s = MSS_EMAC(dev);
> +
> +    address_space_init(&s->dma_as,
> +                       s->dma_mr ? s->dma_mr : get_system_memory(), "dma");

Let's avoid get_system_memory() and use a proper memory region via a
link property:

    if (!s->dma_mr) {
        error_setg(errp, "MSS_EMAC 'ahb-bus' link not set");
        return;
    }
    address_space_init(&s->dma_as, s->dma_mr, "emac-ahb");

> +
> +    qemu_macaddr_default_if_unset(&s->conf.macaddr);
> +    s->nic = qemu_new_nic(&net_msf2_emac_info, &s->conf,
> +                          object_get_typename(OBJECT(dev)), dev->id, s);
> +    qemu_format_nic_info_str(qemu_get_queue(s->nic), s->conf.macaddr.a);
> +}
> +
> +static void msf2_emac_init(Object *obj)
> +{
> +    MSF2EmacState *s = MSS_EMAC(obj);
> +
> +    sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);
> +
> +    memory_region_init_io(&s->mmio, obj, &emac_ops, s,
> +                          "msf2-emac", R_MAX * 4);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
> +}
> +
> +static Property msf2_emac_properties[] = {

    DEFINE_PROP_LINK("ahb-bus", MSF2EmacState, dma_mr,
                     TYPE_MEMORY_REGION, MemoryRegion *),

> +    DEFINE_NIC_PROPERTIES(MSF2EmacState, conf),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static const VMStateDescription vmstate_msf2_emac = {
> +    .name = TYPE_MSS_EMAC,
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(rx_desc, MSF2EmacState),
> +        VMSTATE_UINT16_ARRAY(phy_regs, MSF2EmacState, PHY_MAX_REGS),

Later we'll move the PHY registers out of the EMAC. Not now...

> +        VMSTATE_UINT32_ARRAY(regs, MSF2EmacState, R_MAX),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static void msf2_emac_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->realize = msf2_emac_realize;
> +    dc->reset = msf2_emac_reset;
> +    dc->vmsd = &vmstate_msf2_emac;
> +    device_class_set_props(dc, msf2_emac_properties);
> +}
> +
> +static const TypeInfo msf2_emac_info = {
> +    .name          = TYPE_MSS_EMAC,
> +    .parent        = TYPE_SYS_BUS_DEVICE,
> +    .instance_size = sizeof(MSF2EmacState),
> +    .instance_init = msf2_emac_init,
> +    .class_init    = msf2_emac_class_init,
> +};
> +
> +static void msf2_emac_register_types(void)
> +{
> +    type_register_static(&msf2_emac_info);
> +}
> +
> +type_init(msf2_emac_register_types)
> diff --git a/include/hw/net/msf2-emac.h b/include/hw/net/msf2-emac.h
> new file mode 100644
> index 0000000..ab0da62
> --- /dev/null
> +++ b/include/hw/net/msf2-emac.h
> @@ -0,0 +1,50 @@
> +/*
> + * QEMU model of the Smartfusion2 Ethernet MAC.
> + *
> + * Copyright (c) 2020 Subbaraya Sundeep <address@hidden>.
> + *
> + * 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 "hw/sysbus.h"

Missing:

  #include "exec/memory.h"

for AddressSpace & MemoryRegion.

> +#include "net/net.h"
> +
> +#define TYPE_MSS_EMAC "msf2-emac"
> +#define MSS_EMAC(obj) \
> +    OBJECT_CHECK(MSF2EmacState, (obj), TYPE_MSS_EMAC)
> +
> +#define R_MAX         (0x1a0 / 4)
> +#define PHY_MAX_REGS  32
> +
> +typedef struct MSF2EmacState {
> +    SysBusDevice parent;
> +
> +    MemoryRegion mmio;
> +    MemoryRegion *dma_mr;
> +    AddressSpace dma_as;
> +
> +    qemu_irq irq;
> +    NICState *nic;
> +    NICConf conf;
> +
> +    uint32_t rx_desc;
> +    uint16_t phy_regs[PHY_MAX_REGS];
> +
> +    uint32_t regs[R_MAX];
> +} MSF2EmacState;
> 

With comments addressed:
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Tested-by: Philippe Mathieu-Daudé <address@hidden>

Few comments, otherwise good patch!

Thanks,

Phil.