Linux设备驱动工程师之路——DM9000网卡驱动程序分析

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);
}