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Linux设备驱动工程师之路——DM9000网卡驱动程序分析

K-Style

转载请注明来自于衡阳师范学院08电2  K-Style  http://blog.csdn.net/ayangke,QQ:843308498 邮箱：yangkeemail@qq.com

 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->ndev = 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);
}