DM9000网卡驱动分析

原文地址：www.embeddedlinux.org.cn/html/yingjianqudong/201110/17-1755.html

DM9000是开发板经采用的网络芯片，是一种高度集成而且功耗很低的高速网络控制器，可以和CPU直连，支持10/100M以太网连接，芯片内部自带16K SARM(3KB用来发送，13KB用来接收).

1.模块初始化

static struct platform_driver dm9000_driver = {       .driver = {           .name    = "dm9000",           .owner   = THIS_MODULE,       },       .probe   = dm9000_probe,       .remove  = __devexit_p(dm9000_drv_remove),       .suspend = dm9000_drv_suspend,       .resume  = dm9000_drv_resume,   };      static int __init   dm9000_init(void)   {       printk(KERN_INFO "%s Ethernet Driver, V%s\n", CARDNAME, DRV_VERSION);          return platform_driver_register(&dm9000_driver);   }   

模块初始化完成了基于platfrom平台的DM9000网卡驱动的注册，当DM9000网卡找到其对应的能处理的platform设备后调用probe函数。

2.DM9000网卡初始化

在probe函数中完成了对DM9000网卡的初始化

DM9000的特性：DM9000地址信号和数据信号复用使用CMD引脚区分它们（CMD为低是读写DM900地址寄存器，CMD为高时读写DM9000数据寄存器），访问DM9000内部寄存器时，先将CMD置低，写DM900地址寄存器，然后将CMD置高，读写DM9000数据寄存器。

static int __devinit   dm9000_probe(struct platform_device *pdev)   {          struct dm9000_plat_data *pdata = pdev->dev.platform_data;       struct board_info *db;  /* Point a board information structure */       struct net_device *ndev;       const unsigned char *mac_src;       int ret = 0;       int iosize;       int i;       u32 id_val;          /* Init network device */       //申请net_device结构       ndev = alloc_etherdev(sizeof(struct board_info));       if (!ndev) {           dev_err(&pdev->dev, "could not allocate device.\n");           return -ENOMEM;       }         //将net_device的parent指针指向platform_device对象，表示该设备挂载platform设备上。       SET_NETDEV_DEV(ndev, &pdev->dev);           dev_dbg(&pdev->dev, "dm9000_probe()\n");          /* setup board info structure */       //获取net_device私有数据结构指针       db = netdev_priv(ndev);       memset(db, 0, sizeof(*db));          //设置相关设备       db->dev = &pdev->dev;       db->ndevndev = ndev;          spin_lock_init(&db->lock);       mutex_init(&db->addr_lock);          INIT_DELAYED_WORK(&db->phy_poll, dm9000_poll_work);              //获取平台设备资源。包括DM9000地址寄存器地址，DM9000数据寄存器地址，和DM900所占用的中断号          db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);       db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);       db->irq_res  = platform_get_resource(pdev, IORESOURCE_IRQ, 0);          if (db->addr_res == NULL || db->data_res == NULL ||           db->irq_res == NULL) {           dev_err(db->dev, "insufficient resources\n");           ret = -ENOENT;           goto out;       }          //申请地址寄存器IO内存区域并映射       iosize = res_size(db->addr_res);       db->addr_req = request_mem_region(db->addr_res->start, iosize,                         pdev->name);          if (db->addr_req == NULL) {           dev_err(db->dev, "cannot claim address reg area\n");           ret = -EIO;           goto out;       }          db->io_addr = ioremap(db->addr_res->start, iosize);          if (db->io_addr == NULL) {           dev_err(db->dev, "failed to ioremap address reg\n");           ret = -EINVAL;           goto out;       }          //申请数据寄存器IO内存区域并映射       iosize = res_size(db->data_res);       db->data_req = request_mem_region(db->data_res->start, iosize,                         pdev->name);          if (db->data_req == NULL) {           dev_err(db->dev, "cannot claim data reg area\n");           ret = -EIO;           goto out;       }          db->io_data = ioremap(db->data_res->start, iosize);          if (db->io_data == NULL) {           dev_err(db->dev, "failed to ioremap data reg\n");           ret = -EINVAL;           goto out;       }          /* fill in parameters for net-dev structure */       ndev->base_addr = (unsigned long)db->io_addr;       ndev->irq    = db->irq_res->start;          //设置数据位宽       /* ensure at least we have a default set of IO routines */       dm9000_set_io(db, iosize);          /* check to see if anything is being over-ridden */       if (pdata != NULL) {           /* check to see if the driver wants to over-ride the            * default IO width */              if (pdata->flags & DM9000_PLATF_8BITONLY)               dm9000_set_io(db, 1);              if (pdata->flags & DM9000_PLATF_16BITONLY)               dm9000_set_io(db, 2);              if (pdata->flags & DM9000_PLATF_32BITONLY)               dm9000_set_io(db, 4);              /* check to see if there are any IO routine            * over-rides */              if (pdata->inblk != NULL)               db->inblk = pdata->inblk;              if (pdata->outblk != NULL)               db->outblk = pdata->outblk;              if (pdata->dumpblk != NULL)               db->dumpblk = pdata->dumpblk;              db->flags = pdata->flags;       }      #ifdef CONFIG_DM9000_FORCE_SIMPLE_PHY_POLL       db->flags |= DM9000_PLATF_SIMPLE_PHY;   #endif          //复位网卡芯片       dm9000_reset(db);          //读取设备ID，判断是否是驱动能够处理的网卡芯片       /* try multiple times, DM9000 sometimes gets the read wrong */       for (i = 0; i < 8; i++) {           id_val  = ior(db, DM9000_VIDL);           id_val |= (u32)ior(db, DM9000_VIDH) << 8;           id_val |= (u32)ior(db, DM9000_PIDL) << 16;           id_val |= (u32)ior(db, DM9000_PIDH) << 24;              if (id_val == DM9000_ID)               break;           dev_err(db->dev, "read wrong id 0x%08x\n", id_val);       }          if (id_val != DM9000_ID) {           dev_err(db->dev, "wrong id: 0x%08x\n", id_val);           ret = -ENODEV;           goto out;       }          /* Identify what type of DM9000 we are working on */          id_val = ior(db, DM9000_CHIPR);       dev_dbg(db->dev, "dm9000 revision 0x%02x\n", id_val);          switch (id_val) {       case CHIPR_DM9000A:           db->type = TYPE_DM9000A;           break;       case CHIPR_DM9000B:           db->type = TYPE_DM9000B;           break;       default:           dev_dbg(db->dev, "ID %02x => defaulting to DM9000E\n", id_val);           db->type = TYPE_DM9000E;       }          /* from this point we assume that we have found a DM9000 */          /* driver system function */       ether_setup(ndev);          //设置网卡芯片的接口函数       ndev->open        = &dm9000_open;       ndev->hard_start_xmit    = &dm9000_start_xmit;       ndev->tx_timeout         = &dm9000_timeout;       ndev->watchdog_timeo = msecs_to_jiffies(watchdog);       ndev->stop        = &dm9000_stop;       ndev->set_multicast_list = &dm9000_hash_table;       ndev->ethtool_ops     = &dm9000_ethtool_ops;       ndev->do_ioctl        = &dm9000_ioctl;      #ifdef CONFIG_NET_POLL_CONTROLLER       ndev->poll_controller     = &dm9000_poll_controller;   #endif          db->msg_enable       = NETIF_MSG_LINK;       db->mii.phy_id_mask  = 0x1f;       db->mii.reg_num_mask = 0x1f;       db->mii.force_media  = 0;       db->mii.full_duplex  = 0;       db->mii.dev       = ndev;       db->mii.mdio_read    = dm9000_phy_read;       db->mii.mdio_write   = dm9000_phy_write;          mac_src = "eeprom";          //从EEPROM中读取MAC地址填充dev_addr       /* try reading the node address from the attached EEPROM */       for (i = 0; i < 6; i += 2)           dm9000_read_eeprom(db, i / 2, ndev->dev_addr+i);          if (!is_valid_ether_addr(ndev->dev_addr) && pdata != NULL) {           mac_src = "platform data";           memcpy(ndev->dev_addr, pdata->dev_addr, 6);       }          if (!is_valid_ether_addr(ndev->dev_addr)) {           /* try reading from mac */                      mac_src = "chip";           for (i = 0; i < 6; i++)               ndev->dev_addr[i] = ior(db, i+DM9000_PAR);       }          if (!is_valid_ether_addr(ndev->dev_addr))           dev_warn(db->dev, "%s: Invalid ethernet MAC address. Please "                "set using ifconfig\n", ndev->name);          //设置平台设备驱动的dev成员为ndev。       platform_set_drvdata(pdev, ndev);          //注册网络设备驱动       ret = register_netdev(ndev);          if (ret == 0)           printk(KERN_INFO "%s: dm9000%c at %p,%p IRQ %d MAC: %pM (%s)\n",                  ndev->name, dm9000_type_to_char(db->type),                  db->io_addr, db->io_data, ndev->irq,                  ndev->dev_addr, mac_src);       return 0;      out:       dev_err(db->dev, "not found (%d).\n", ret);          dm9000_release_board(pdev, db);       free_netdev(ndev);          return ret;   }   

我们在来看看读写网卡寄存器所用的ior和iow

static u8   ior(board_info_t * db, int reg)   {       writeb(reg, db->io_addr);       return readb(db->io_data);   }      static void   iow(board_info_t * db, int reg, int value)   {       writeb(reg, db->io_addr);       writeb(value, db->io_data);   } 

可以看得出是先将要访问的寄存器地址写入到地址寄存器，然后在将数据写入到数据寄存器。地址。

3.打开网卡

在linux终端下使用ifconfig命令时调用net_device的open函数打开网卡设备

static int   dm9000_open(struct net_device *dev)   {       board_info_t *db = netdev_priv(dev);       unsigned long irqflags = db->irq_res->flags & IRQF_TRIGGER_MASK;          if (netif_msg_ifup(db))           dev_dbg(db->dev, "enabling %s\n", dev->name);          /* If there is no IRQ type specified, default to something that        * may work, and tell the user that this is a problem */          if (irqflags == IRQF_TRIGGER_NONE)           dev_warn(db->dev, "WARNING: no IRQ resource flags set.\n");          irqflags |= IRQF_SHARED;          //申请中断       if (request_irq(dev->irq, &dm9000_interrupt, irqflags, dev->name, dev))           return -EAGAIN;          /* Initialize DM9000 board */       //复位网卡芯片       dm9000_reset(db);          //初始化网卡（相关寄存器设置）       dm9000_init_dm9000(dev);          /* Init driver variable */       db->dbug_cnt = 0;          mii_check_media(&db->mii, netif_msg_link(db), 1);          //打开发送队列       netif_start_queue(dev);              //调度发送队列开始工作       dm9000_schedule_poll(db);          return 0;   }    

4.数据发送

下面说一下DM9000A中的存储部分，DM9000A内部有一个4K Dword SRAM，其中3KB是作为发送，16KB作为接收，如下图所示。其中0x0000~0x0BFF是传说中的TX buffer(TX buffer中只能存放两个包)，0x0C00~0x3FFF是RX buffer。因此在写内存操作时，当IMR的第7位被设置，如果到达了地址的结尾比如到了3KB，则回卷到0。相似的方式，在读操作中，当IMR的第7位被设置如果到达了地址的结尾比如16K，则回卷到0x0C00。

DM9000的TX RAM可以同时放两个包，可以第9行代码中看出如果大于TXRAM中的包大于2则返回，DM9000会先发送第一个包，然后再发第二个包。

static int   dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)   {       unsigned long flags;       board_info_t *db = netdev_priv(dev);          dm9000_dbg(db, 3, "%s:\n", __func__);          //如果TX RAM中的包大于2个包则返回       if (db->tx_pkt_cnt > 1)           return 1;          spin_lock_irqsave(&db->lock, flags);          *MWCMD是Memory data write command with address increment Register(F8H)         *将要访问的TXRAM地址写入地址寄存器。          /* Move data to DM9000 TX RAM */       writeb(DM9000_MWCMD, db->io_addr);          //拷贝数据到TXRAM       (db->outblk)(db->io_data, skb->data, skb->len);       dev->stats.tx_bytes += skb->len;          db->tx_pkt_cnt++;//增加数据包计数，这个值会在发送完成中断时进行自减          如果是第一个包则直接发送       /* TX control: First packet immediately send, second packet queue */       if (db->tx_pkt_cnt == 1) {              /* Set TX length to DM9000 */         /*把数据的长度填到TXPLL(发送包长度低字节)和TXPLH(发送包长度高字节)中*/             iow(db, DM9000_TXPLL, skb->len);             iow(db, DM9000_TXPLH, skb->len >> 8);             /*置发送控制寄存器(TX Control Register)的发送请求位TXREQ(Auto clears after sending completely)，这样就可以发送出去了*/           /*             *记下此时的时间，这里起一个时间戳的作用，之后的超时会用到。如果当前的系统时间超过设备的trans_start时间             *至少一个超时周期，网络层将最终调用驱动程序的tx_timeout。那个这个"一个超时周期"又是什么呢？这个是我们在                 *probe函数中设置的,ndev->watchdog_timeo = msecs_to_jiffies(watchdog);             */           dev->trans_start = jiffies;  /* save the time stamp */       } else {           //如果是第二个包，则暂时不发送，等待第一个包发送完成时tx_pkt_cnt减为1的时候再发送。           /* Second packet */           db->queue_pkt_len = skb->len;           netif_stop_queue(dev);//停止发送队列       }          spin_unlock_irqrestore(&db->lock, flags);          /* free this SKB */       dev_kfree_skb(skb);          return 0;   }   

4.中断

static irqreturn_t dm9000_interrupt(intirq, void *dev_id)   {            structnet_device *dev = dev_id;            board_info_t*db = netdev_priv(dev);            intint_status;            unsignedlong flags;            u8reg_save;                dm9000_dbg(db,3, "entering %s\n", __func__);                /*A real interrupt coming */                //禁止所用中断            /*holders of db->lock must always block IRQs */            spin_lock_irqsave(&db->lock,flags);                //保存寄存器地址            /*Save previous register address */            reg_save= readb(db->io_addr);                //禁止DM9000的所有中断            /*Disable all interrupts */            iow(db,DM9000_IMR, IMR_PAR);                /*Got DM9000 interrupt status */            //获取中断状态寄存器的值            int_status= ior(db, DM9000_ISR); /* Got ISR */            iow(db,DM9000_ISR, int_status); /* Clear ISRstatus */                if(netif_msg_intr(db))                      dev_dbg(db->dev,"interrupt status %02x\n", int_status);                /*Received the coming packet */            //如果是读取中断，则开始读取            if(int_status & ISR_PRS)                      dm9000_rx(dev);                /*Trnasmit Interrupt check */            //是发送完成中断则处理发送完成后的事情            if(int_status & ISR_PTS)                      dm9000_tx_done(dev,db);                if(db->type != TYPE_DM9000E) {                      if(int_status & ISR_LNKCHNG) {                               /*fire a link-change request */                               schedule_delayed_work(&db->phy_poll,1);                      }            }                /*Re-enable interrupt mask */            //重新打开DM9000的内部中断            iow(db,DM9000_IMR, db->imr_all);                /*Restore previous register address */            //恢复寄存器的值            writeb(reg_save,db->io_addr);                //重新允许所有中断            spin_unlock_irqrestore(&db->lock,flags);                returnIRQ_HANDLED;   }   

5.接收数据

static void   dm9000_rx(struct net_device *dev)   {       board_info_t *db = netdev_priv(dev);       struct dm9000_rxhdr rxhdr;       struct sk_buff *skb;       u8 rxbyte, *rdptr;       bool GoodPacket;       int RxLen;          /* Check packet ready or not */       do {           ior(db, DM9000_MRCMDX); /* Dummy read */              //获取接收数据的长度           /* Get most updated data */           rxbyte = readb(db->io_data);              //检查设备接收状态           /* Status check: this byte must be 0 or 1 */           if (rxbyte > DM9000_PKT_RDY) {               dev_warn(db->dev, "status check fail: %d\n", rxbyte);               iow(db, DM9000_RCR, 0x00);  /* Stop Device */               iow(db, DM9000_ISR, IMR_PAR);   /* Stop INT request */               return;           }              if (rxbyte != DM9000_PKT_RDY)               return;                         /* A packet ready now  & Get status/length */           GoodPacket = true;           writeb(DM9000_MRCMD, db->io_addr);              (db->inblk)(db->io_data, &rxhdr, sizeof(rxhdr));              RxLen = le16_to_cpu(rxhdr.RxLen);              if (netif_msg_rx_status(db))               dev_dbg(db->dev, "RX: status %02x, length %04x\n",                   rxhdr.RxStatus, RxLen);              /* Packet Status check */           if (RxLen < 0x40) {               GoodPacket = false;               if (netif_msg_rx_err(db))                   dev_dbg(db->dev, "RX: Bad Packet (runt)\n");           }              if (RxLen > DM9000_PKT_MAX) {               dev_dbg(db->dev, "RST: RX Len:%x\n", RxLen);           }              /* rxhdr.RxStatus is identical to RSR register. */           if (rxhdr.RxStatus & (RSR_FOE | RSR_CE | RSR_AE |                         RSR_PLE | RSR_RWTO |                         RSR_LCS | RSR_RF)) {               GoodPacket = false;               if (rxhdr.RxStatus & RSR_FOE) {                   if (netif_msg_rx_err(db))                       dev_dbg(db->dev, "fifo error\n");                   dev->stats.rx_fifo_errors++;               }               if (rxhdr.RxStatus & RSR_CE) {                   if (netif_msg_rx_err(db))                       dev_dbg(db->dev, "crc error\n");                   dev->stats.rx_crc_errors++;               }               if (rxhdr.RxStatus & RSR_RF) {                   if (netif_msg_rx_err(db))                       dev_dbg(db->dev, "length error\n");                   dev->stats.rx_length_errors++;               }           }              /* Move data from DM9000 */           //如果接收正确，开始接收           if (GoodPacket               && ((skb = dev_alloc_skb(RxLen + 4)) != NULL)) {               skb_reserve(skb, 2);               rdptr = (u8 *) skb_put(skb, RxLen - 4);//获取skb的数据指针                  /* Read received packet from RX SRAM */                  (db->inblk)(db->io_data, rdptr, RxLen);//读取数据               dev->stats.rx_bytes += RxLen;                  /* Pass to upper layer */               skb->protocol = eth_type_trans(skb, dev);               netif_rx(skb);//将接收到的skb交给协议层               dev->stats.rx_packets++;              } else {               /* need to dump the packet's data */                  (db->dumpblk)(db->io_data, RxLen);           }       } while (rxbyte == DM9000_PKT_RDY);   }   

6.发送完成

static void dm9000_tx_done(struct net_device *dev, board_info_t *db)   {       int tx_status = ior(db, DM9000_NSR);    /* Got TX status */          if (tx_status & (NSR_TX2END | NSR_TX1END)) {           /* One packet sent complete */              //将数据包计数减1           db->tx_pkt_cnt--;           dev->stats.tx_packets++;              if (netif_msg_tx_done(db))               dev_dbg(db->dev, "tx done, NSR %02x\n", tx_status);              /* Queue packet check & send */           //如果数据包数量依然大于0，说明是TX RAM中的第二个包，再次启动发送，将TX RAM中第二个包发送出去           if (db->tx_pkt_cnt > 0) {             /*把数据的长度填到TXPLL(发送包长度低字节)和TXPLH(发送包长度高字节)中*/             iow(db, DM9000_TXPLL, skb->len);             iow(db, DM9000_TXPLH, skb->len >> 8);             /*置发送控制寄存器(TX Control Register)的发送请求位TXREQ(Auto clears after sending completely)，这样就可以发送出去了*/                dev->trans_start = jiffies;           }           netif_wake_queue(dev);//唤醒发送队列       }   } 

7.超时处理

static void dm9000_timeout(struct net_device *dev)   {       board_info_t *db = netdev_priv(dev);       u8 reg_save;       unsigned long flags;          /* Save previous register address */       reg_save = readb(db->io_addr);       spin_lock_irqsave(&db->lock, flags);          //停止发送队列并复位DM9000网卡       netif_stop_queue(dev);       dm9000_reset(db);       dm9000_init_dm9000(dev);       /* We can accept TX packets again */          //重新发送       dev->trans_start = jiffies;       netif_wake_queue(dev);          /* Restore previous register address */       writeb(reg_save, db->io_addr);       spin_unlock_irqrestore(&db->lock, flags);   }