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linux网络流程分析(一)---网卡驱动_phy reset is blocked due to sol/ider session

phy reset is blocked due to sol/ider session

分析linux网络的书已经很多了,包括《追踪Linux TCP/IP代码运行》《Linux内核源码剖析——TCP/IP实现》,这里我只是从数据包在linux内核中的基本流程来分析,尽可能的展现一个主流程框架。

内核如何从网卡接收数据,传统的过程:
1.数据到达网卡;
2.网卡产生一个中断给内核;
3.内核使用I/O指令,从网卡I/O区域中去读取数据;

 
我们在许多网卡驱动中(很老那些),都可以在网卡的中断函数中见到这一过程。
 
但是,这一种方法,有一种重要的问题,就是大流量的数据来到,网卡会产生大量的中断,内核在中断上下文 中,会浪费大量的资源来处理中断本身。所以,就有一个问题,“可不可以不使用中断”,这就是轮询技术,所谓NAPI技术,说来也不神秘,就是说,内核屏蔽 中断,然后隔一会儿就去问网卡,“你有没有数据啊?”……
 
从这个描述本身可以看到,如果数据量少,轮询同样占用大量的不必要的CPU资源,大家各有所长吧
 
OK,另一个问题,就是从网卡的I/O区域,包括I/O寄存器或I/O内存中去读取数据,这都要CPU 去读,也要占用CPU资源,“CPU从I/O区域读,然后把它放到内存(这个内存指的是系统本身的物理内存,跟外设的内存不相干,也叫主内存)中”。于是 自然地,就想到了DMA技术——让网卡直接从主内存之间读写它们的I/O数据,CPU,这儿不干你事,自己找乐子去:
1.首先,内核在主内存中为收发数据建立一个环形的缓冲队列(通常叫DMA环形缓冲区)。
2.内核将这个缓冲区通过DMA映射,把这个队列交给网卡;
3.网卡收到数据,就直接放进这个环形缓冲区了——也就是直接放进主内存了;然后,向系统产生一个中断;
4.内核收到这个中断,就取消DMA映射,这样,内核就直接从主内存中读取数据;
 
——呵呵,这一个过程比传统的过程少了不少工作,因为设备直接把数据放进了主内存,不需要CPU的干预,效率是不是提高不少?
 
对应以上4步,来看它的具体实现:
1)分配环形DMA缓冲区
Linux内核中,用skb来描述一个缓存,所谓分配,就是建立一定数量的skb,然后用e1000_rx_ring 环形缓冲区队列描述符连接起来
2)建立DMA映射
内核通过调用
dma_map_single(struct device *dev,void *buffer,size_t size,enum dma_data_direction direction)
建立映射关系。
struct device *dev 描述一个设备;
buffer:把哪个地址映射给设备;也就是某一个skb——要映射全部,当然是做一个双向链表的循环即可;
size:缓存大小;
direction:映射方向——谁传给谁:一般来说,是“双向”映射,数据在设备和内存之间双向流动;
对于PCI设备而言(网卡一般是PCI的),通过另一个包裹函数pci_map_single,这样,就把buffer交给设备了!设备可以直接从里边读/取数据。
3)这一步由硬件完成;
4)取消映射
dma_unmap_single,对PCI而言,大多调用它的包裹函数pci_unmap_single,不取消的话,缓存控制权还在设备手里,要调用 它,把主动权掌握在CPU手里——因为我们已经接收到数据了,应该由CPU把数据交给上层网络栈;当然,不取消之前,通常要读一些状态位信息,诸如此类, 一般是调用dma_sync_single_for_cpu()让CPU在取消映射前,就可以访问DMA缓冲区中的内容

首先,数据包从网卡光电信号来之后,先经过网卡驱动,转换成skb,进入链路层,那么我首先就先分析一下网卡驱动的流程。

源码位置:Driver/net/E1000e文件夹下面。

static int __init e1000_init_module( void )
{注册网卡驱动,按照PCI驱动开发方式来进行注册
     int ret;
     printk(KERN_INFO "%s: Intel(R) PRO/1000 Network Driver - %s\n" ,
            e1000e_driver_name, e1000e_driver_version);
     printk(KERN_INFO "%s: Copyright (c) 1999-2008 Intel Corporation.\n" ,
            e1000e_driver_name);
     ret = pci_register_driver(&e1000_driver);
     pm_qos_add_requirement(PM_QOS_CPU_DMA_LATENCY, e1000e_driver_name,
                    PM_QOS_DEFAULT_VALUE);
                 
     return ret;
}

  然后看一下驱动结构体内容,这里不对PCI类型驱动开发做介绍了。

/* PCI Device API Driver */
static struct pci_driver e1000_driver = {
     .name     = e1000e_driver_name,
     .id_table = e1000_pci_tbl,
     .probe    = e1000_probe,
     .remove   = __devexit_p(e1000_remove),
#ifdef CONFIG_PM
     /* Power Management Hooks */
     .suspend  = e1000_suspend,
     .resume   = e1000_resume,
#endif
     .shutdown = e1000_shutdown,
     .err_handler = &e1000_err_handler
};

  这里面最重要的函数是e1000_probe,先看一下这个函数的作用是什么:“Device Initialization Routine”,这个应该不难理解。

static int __devinit e1000_probe( struct pci_dev *pdev,
                  const struct pci_device_id *ent)
{
     struct net_device *netdev;
     struct e1000_adapter *adapter;
     struct e1000_hw *hw;
     const struct e1000_info *ei = e1000_info_tbl[ent->driver_data];
     resource_size_t mmio_start, mmio_len;
     resource_size_t flash_start, flash_len;
 
     static int cards_found;
     int i, err, pci_using_dac;
     u16 eeprom_data = 0;
     u16 eeprom_apme_mask = E1000_EEPROM_APME;
 
     e1000e_disable_l1aspm(pdev);
从这里开始对设备驱动进行初始化,包括名称、内存之类的。
     err = pci_enable_device_mem(pdev);
     if (err)
         return err;
 
     pci_using_dac = 0;
     err = pci_set_dma_mask(pdev, DMA_BIT_MASK(64));
     if (!err) {
         err = pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64));
         if (!err)
             pci_using_dac = 1;
     } else {
         err = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
         if (err) {
             err = pci_set_consistent_dma_mask(pdev,
                               DMA_BIT_MASK(32));
             if (err) {
                 dev_err(&pdev->dev, "No usable DMA "
                     "configuration, aborting\n" );
                 goto err_dma;
             }
         }
     }
 
     err = pci_request_selected_regions_exclusive(pdev,
                                       pci_select_bars(pdev, IORESOURCE_MEM),
                                       e1000e_driver_name);
     if (err)
         goto err_pci_reg;
 
     /* AER (Advanced Error Reporting) hooks */
     err = pci_enable_pcie_error_reporting(pdev);
     if (err) {
         dev_err(&pdev->dev, "pci_enable_pcie_error_reporting failed "
                 "0x%x\n" , err);
         /* non-fatal, continue */
     }
 
     pci_set_master(pdev);
     /* PCI config space info */
     err = pci_save_state(pdev);
     if (err)
         goto err_alloc_etherdev;
 
     err = -ENOMEM;<br>这里要为驱动分配一个容器之类的,因为驱动后面的一切操作都是在它的基础之上。
     netdev = alloc_etherdev( sizeof ( struct e1000_adapter));
     if (!netdev)
         goto err_alloc_etherdev;
 
     SET_NETDEV_DEV(netdev, &pdev->dev);
 
     pci_set_drvdata(pdev, netdev);
     adapter = netdev_priv(netdev);
     hw = &adapter->hw;
     adapter->netdev = netdev;
     adapter->pdev = pdev;
     adapter->ei = ei;
     adapter->pba = ei->pba;
     adapter->flags = ei->flags;
     adapter->flags2 = ei->flags2;
     adapter->hw.adapter = adapter;
     adapter->hw.mac.type = ei->mac;
     adapter->max_hw_frame_size = ei->max_hw_frame_size;
     adapter->msg_enable = (1 << NETIF_MSG_DRV | NETIF_MSG_PROBE) - 1;
<span>0表示设备映射的内存的的bar</span>
     mmio_start = pci_resource_start(pdev, 0);
     mmio_len = pci_resource_len(pdev, 0);
 
     err = -EIO;<br>这里我的理解是容器的硬件地址与bar进行映射,hw_addr代表的是网卡的硬件地址
     adapter->hw.hw_addr = ioremap(mmio_start, mmio_len);
     if (!adapter->hw.hw_addr)
         goto err_ioremap;
 
     if ((adapter->flags & FLAG_HAS_FLASH) &&
         (pci_resource_flags(pdev, 1) & IORESOURCE_MEM)) {
         flash_start = pci_resource_start(pdev, 1);
         flash_len = pci_resource_len(pdev, 1);
         adapter->hw.flash_address = ioremap(flash_start, flash_len);
         if (!adapter->hw.flash_address)
             goto err_flashmap;
     }
 
     /* construct the net_device struct */
     netdev->netdev_ops       = &e1000e_netdev_ops;
     e1000e_set_ethtool_ops(netdev);
     netdev->watchdog_timeo       = 5 * HZ;
     netif_napi_add(netdev, &adapter->napi, e1000_clean, 64);
     strncpy(netdev->name, pci_name(pdev), sizeof (netdev->name) - 1);
 
     netdev->mem_start = mmio_start;
     netdev->mem_end = mmio_start + mmio_len;
 
     adapter->bd_number = cards_found++;
 
     e1000e_check_options(adapter);
 
     /* setup adapter struct */
     err = e1000_sw_init(adapter);
     if (err)
         goto err_sw_init;
 
     err = -EIO;
 
     memcpy(&hw->mac.ops, ei->mac_ops, sizeof (hw->mac.ops));
     memcpy(&hw->nvm.ops, ei->nvm_ops, sizeof (hw->nvm.ops));
     memcpy(&hw->phy.ops, ei->phy_ops, sizeof (hw->phy.ops));
 
     err = ei->get_variants(adapter);
     if (err)
         goto err_hw_init;
 
     if ((adapter->flags & FLAG_IS_ICH) &&
         (adapter->flags & FLAG_READ_ONLY_NVM))
         e1000e_write_protect_nvm_ich8lan(&adapter->hw);
 
     hw->mac.ops.get_bus_info(&adapter->hw);
 
     adapter->hw.phy.autoneg_wait_to_complete = 0;
 
     /* Copper options */
     if (adapter->hw.phy.media_type == e1000_media_type_copper) {
         adapter->hw.phy.mdix = AUTO_ALL_MODES;
         adapter->hw.phy.disable_polarity_correction = 0;
         adapter->hw.phy.ms_type = e1000_ms_hw_default;
     }
 
     if (e1000_check_reset_block(&adapter->hw))
         e_info( "PHY reset is blocked due to SOL/IDER session.\n" );
 
     netdev->features = NETIF_F_SG |
                NETIF_F_HW_CSUM |
                NETIF_F_HW_VLAN_TX |
                NETIF_F_HW_VLAN_RX;
 
     if (adapter->flags & FLAG_HAS_HW_VLAN_FILTER)
         netdev->features |= NETIF_F_HW_VLAN_FILTER;
 
     netdev->features |= NETIF_F_TSO;
     netdev->features |= NETIF_F_TSO6;
 
     netdev->vlan_features |= NETIF_F_TSO;
     netdev->vlan_features |= NETIF_F_TSO6;
     netdev->vlan_features |= NETIF_F_HW_CSUM;
     netdev->vlan_features |= NETIF_F_SG;
 
     if (pci_using_dac)
         netdev->features |= NETIF_F_HIGHDMA;
 
     if (e1000e_enable_mng_pass_thru(&adapter->hw))
         adapter->flags |= FLAG_MNG_PT_ENABLED;
 
     /*
      * before reading the NVM, reset the controller to
      * put the device in a known good starting state
      */
     adapter->hw.mac.ops.reset_hw(&adapter->hw);
 
     /*
      * systems with ASPM and others may see the checksum fail on the first
      * attempt. Let's give it a few tries
      */
     for (i = 0;; i++) {
         if (e1000_validate_nvm_checksum(&adapter->hw) >= 0)
             break ;
         if (i == 2) {
             e_err( "The NVM Checksum Is Not Valid\n" );
             err = -EIO;
             goto err_eeprom;
         }
     }
 
     e1000_eeprom_checks(adapter);
 
     /* copy the MAC address out of the NVM */
     if (e1000e_read_mac_addr(&adapter->hw))
         e_err( "NVM Read Error while reading MAC address\n" );
 
     memcpy(netdev->dev_addr, adapter->hw.mac.addr, netdev->addr_len);
     memcpy(netdev->perm_addr, adapter->hw.mac.addr, netdev->addr_len);
 
     if (!is_valid_ether_addr(netdev->perm_addr)) {
         e_err( "Invalid MAC Address: %pM\n" , netdev->perm_addr);
         err = -EIO;
         goto err_eeprom;
     }
 
     init_timer(&adapter->watchdog_timer);
     adapter->watchdog_timer.function = &e1000_watchdog;
     adapter->watchdog_timer.data = (unsigned long ) adapter;
 
     init_timer(&adapter->phy_info_timer);
     adapter->phy_info_timer.function = &e1000_update_phy_info;
     adapter->phy_info_timer.data = (unsigned long ) adapter;
 
     INIT_WORK(&adapter->reset_task, e1000_reset_task);
     INIT_WORK(&adapter->watchdog_task, e1000_watchdog_task);
     INIT_WORK(&adapter->downshift_task, e1000e_downshift_workaround);
     INIT_WORK(&adapter->update_phy_task, e1000e_update_phy_task);
 
     /* Initialize link parameters. User can change them with ethtool */
     adapter->hw.mac.autoneg = 1;
     adapter->fc_autoneg = 1;
     adapter->hw.fc.requested_mode = e1000_fc_default;
     adapter->hw.fc.current_mode = e1000_fc_default;
     adapter->hw.phy.autoneg_advertised = 0x2f;
这里是默认的接收环和发送环大小是256,其实一次中断,能接受的数据不会有太高,我做实验的时候也就是1个2个。这里的环不是一直存放skb_buff,而是DMA一次中断后能给内核的数据存放地,当中断结束后,skb_buff会被转移的。
     /* ring size defaults */
     adapter->rx_ring->count = 256;
     adapter->tx_ring->count = 256;
 
     /*
      * Initial Wake on LAN setting - If APM wake is enabled in
      * the EEPROM, enable the ACPI Magic Packet filter
      */
     if (adapter->flags & FLAG_APME_IN_WUC) {
         /* APME bit in EEPROM is mapped to WUC.APME */
         eeprom_data = er32(WUC);
         eeprom_apme_mask = E1000_WUC_APME;
         if (eeprom_data & E1000_WUC_PHY_WAKE)
             adapter->flags2 |= FLAG2_HAS_PHY_WAKEUP;
     } else if (adapter->flags & FLAG_APME_IN_CTRL3) {
         if (adapter->flags & FLAG_APME_CHECK_PORT_B &&
             (adapter->hw.bus.func == 1))
             e1000_read_nvm(&adapter->hw,
                 NVM_INIT_CONTROL3_PORT_B, 1, &eeprom_data);
         else
             e1000_read_nvm(&adapter->hw,
                 NVM_INIT_CONTROL3_PORT_A, 1, &eeprom_data);
     }
 
     /* fetch WoL from EEPROM */
     if (eeprom_data & eeprom_apme_mask)
         adapter->eeprom_wol |= E1000_WUFC_MAG;
 
     /*
      * now that we have the eeprom settings, apply the special cases
      * where the eeprom may be wrong or the board simply won't support
      * wake on lan on a particular port
      */
     if (!(adapter->flags & FLAG_HAS_WOL))
         adapter->eeprom_wol = 0;
 
     /* initialize the wol settings based on the eeprom settings */
     adapter->wol = adapter->eeprom_wol;
     device_set_wakeup_enable(&adapter->pdev->dev, adapter->wol);
 
     /* save off EEPROM version number */
     e1000_read_nvm(&adapter->hw, 5, 1, &adapter->eeprom_vers);
 
     /* reset the hardware with the new settings */
     e1000e_reset(adapter);
 
     /*
      * If the controller has AMT, do not set DRV_LOAD until the interface
      * is up.  For all other cases, let the f/w know that the h/w is now
      * under the control of the driver.
      */
     if (!(adapter->flags & FLAG_HAS_AMT))
         e1000_get_hw_control(adapter);
 
     strcpy(netdev->name, "eth%d" );<br>注册网卡驱动
     err = register_netdev(netdev);
     if (err)
         goto err_register;
 
     /* carrier off reporting is important to ethtool even BEFORE open */
     netif_carrier_off(netdev);
 
     e1000_print_device_info(adapter);
 
     return 0;
 
err_register:
     if (!(adapter->flags & FLAG_HAS_AMT))
         e1000_release_hw_control(adapter);
err_eeprom:
     if (!e1000_check_reset_block(&adapter->hw))
         e1000_phy_hw_reset(&adapter->hw);
err_hw_init:
 
     kfree(adapter->tx_ring);
     kfree(adapter->rx_ring);
err_sw_init:
     if (adapter->hw.flash_address)
         iounmap(adapter->hw.flash_address);
     e1000e_reset_interrupt_capability(adapter);
err_flashmap:
     iounmap(adapter->hw.hw_addr);
err_ioremap:
     free_netdev(netdev);
err_alloc_etherdev:
     pci_release_selected_regions(pdev,
                                  pci_select_bars(pdev, IORESOURCE_MEM));
err_pci_reg:
err_dma:
     pci_disable_device(pdev);
     return err;
}

  通过上面的函数,我们完成了驱动的初始化和设备注册工作。下面是网卡设备注册的操作函数

static const struct net_device_ops e1000e_netdev_ops = {
     .ndo_open       = e1000_open,
     .ndo_stop       = e1000_close,
     .ndo_start_xmit     = e1000_xmit_frame,
     .ndo_get_stats      = e1000_get_stats,
     .ndo_set_multicast_list = e1000_set_multi,
     .ndo_set_mac_address    = e1000_set_mac,
     .ndo_change_mtu     = e1000_change_mtu,
     .ndo_do_ioctl       = e1000_ioctl,
     .ndo_tx_timeout     = e1000_tx_timeout,
     .ndo_validate_addr  = eth_validate_addr,
 
     .ndo_vlan_rx_register   = e1000_vlan_rx_register,
     .ndo_vlan_rx_add_vid    = e1000_vlan_rx_add_vid,
     .ndo_vlan_rx_kill_vid   = e1000_vlan_rx_kill_vid,
#ifdef CONFIG_NET_POLL_CONTROLLER
     .ndo_poll_controller    = e1000_netpoll,
#endif
};

  这里关注一下最后一个函数

static void e1000_netpoll( struct net_device *netdev)
{
     struct e1000_adapter *adapter = netdev_priv(netdev);
 
     disable_irq(adapter->pdev->irq);这里关闭容器设备中断
     e1000_intr(adapter->pdev->irq, netdev); 初始化设备中断
 
     enable_irq(adapter->pdev->irq);
}

  这是网卡驱动的中断处理函数,也就是后半段的处理

static irqreturn_t e1000_intr( int irq, void *data)
{
     struct net_device *netdev = data;
     struct e1000_adapter *adapter = netdev_priv(netdev);
     struct e1000_hw *hw = &adapter->hw;
     u32 rctl, icr = er32(ICR);
 
     if (!icr)
         return IRQ_NONE;  /* Not our interrupt */
 
     /*
      * IMS will not auto-mask if INT_ASSERTED is not set, and if it is
      * not set, then the adapter didn't send an interrupt
      */
     if (!(icr & E1000_ICR_INT_ASSERTED))
         return IRQ_NONE;
 
     /*
      * Interrupt Auto-Mask...upon reading ICR,
      * interrupts are masked.  No need for the
      * IMC write
      */
 
     if (icr & E1000_ICR_LSC) {
         hw->mac.get_link_status = 1;
         /*
          * ICH8 workaround-- Call gig speed drop workaround on cable
          * disconnect (LSC) before accessing any PHY registers
          */
         if ((adapter->flags & FLAG_LSC_GIG_SPEED_DROP) &&
             (!(er32(STATUS) & E1000_STATUS_LU)))
             schedule_work(&adapter->downshift_task);
 
         /*
          * 80003ES2LAN workaround--
          * For packet buffer work-around on link down event;
          * disable receives here in the ISR and
          * reset adapter in watchdog
          */
         if (netif_carrier_ok(netdev) &&
             (adapter->flags & FLAG_RX_NEEDS_RESTART)) {
             /* disable receives */
             rctl = er32(RCTL);
             ew32(RCTL, rctl & ~E1000_RCTL_EN);
             adapter->flags |= FLAG_RX_RESTART_NOW;
         }
         /* guard against interrupt when we're going down */
         if (!test_bit(__E1000_DOWN, &adapter->state))
             mod_timer(&adapter->watchdog_timer, jiffies + 1);
     }
这里调用了_napi_schedule完成将设备的napi队列挂到CPU
     if (napi_schedule_prep(&adapter->napi)) {
         adapter->total_tx_bytes = 0;
         adapter->total_tx_packets = 0;
         adapter->total_rx_bytes = 0;
         adapter->total_rx_packets = 0;
         __napi_schedule(&adapter->napi);
     }
 
     return IRQ_HANDLED;
}

  

void __napi_schedule( struct napi_struct *n)
{
     unsigned long flags;
 
     local_irq_save(flags);
     list_add_tail(&n->poll_list, &__get_cpu_var(softnet_data).poll_list); //adapter里面的队列地址挂到poll.list中
     //设置软中断NET_RX_SOFTIRQ,等待调度其中断处理程序
     __raise_softirq_irqoff(NET_RX_SOFTIRQ);
     local_irq_restore(flags);
}

  再看一下如何打开网络设备

static int e1000_open( struct net_device *netdev)
{
     struct e1000_adapter *adapter = netdev_priv(netdev);
     struct e1000_hw *hw = &adapter->hw;
     int err;
 
     /* disallow open during test */
     if (test_bit(__E1000_TESTING, &adapter->state))
         return -EBUSY;
 
     netif_carrier_off(netdev);
初始化传输和接收描述符,这里主要是对接收环和发送环进行初始化,他们需要256个单元空间
     /* allocate transmit descriptors */
     err = e1000e_setup_tx_resources(adapter);
     if (err)
         goto err_setup_tx;
 
     /* allocate receive descriptors */
     err = e1000e_setup_rx_resources(adapter);
     if (err)
         goto err_setup_rx;
 
     e1000e_power_up_phy(adapter);
 
     adapter->mng_vlan_id = E1000_MNG_VLAN_NONE;
     if ((adapter->hw.mng_cookie.status &
          E1000_MNG_DHCP_COOKIE_STATUS_VLAN))
         e1000_update_mng_vlan(adapter);
 
     /*
      * If AMT is enabled, let the firmware know that the network
      * interface is now open
      */
     if (adapter->flags & FLAG_HAS_AMT)
         e1000_get_hw_control(adapter);
 
     /*
      * before we allocate an interrupt, we must be ready to handle it.
      * Setting DEBUG_SHIRQ in the kernel makes it fire an interrupt
      * as soon as we call pci_request_irq, so we have to setup our
      * clean_rx handler before we do so.
      */ 这个函数比较重要,在这里面完成对容器的配置,包括软中断设置
     e1000_configure(adapter);
{
static void e1000_configure( struct e1000_adapter *adapter)
{
     e1000_set_multi(adapter->netdev);
 
     e1000_restore_vlan(adapter);
     e1000_init_manageability(adapter);
 
     e1000_configure_tx(adapter);配置发送
     e1000_setup_rctl(adapter);
     e1000_configure_rx(adapter);配置接收
     adapter->alloc_rx_buf(adapter, e1000_desc_unused(adapter->rx_ring));
}
}
     err = e1000_request_irq(adapter);
     if (err)
         goto err_req_irq;
 
     /*
      * Work around PCIe errata with MSI interrupts causing some chipsets to
      * ignore e1000e MSI messages, which means we need to test our MSI
      * interrupt now
      */
     if (adapter->int_mode != E1000E_INT_MODE_LEGACY) {
         err = e1000_test_msi(adapter);
         if (err) {
             e_err( "Interrupt allocation failed\n" );
             goto err_req_irq;
         }
     }
 
     /* From here on the code is the same as e1000e_up() */
     clear_bit(__E1000_DOWN, &adapter->state);
 
     napi_enable(&adapter->napi);
 
     e1000_irq_enable(adapter);
 
     netif_start_queue(netdev);
 
     /* fire a link status change interrupt to start the watchdog */
     ew32(ICS, E1000_ICS_LSC);
 
     return 0;
 
err_req_irq:
     e1000_release_hw_control(adapter);
     e1000_power_down_phy(adapter);
     e1000e_free_rx_resources(adapter);
err_setup_rx:
     e1000e_free_tx_resources(adapter);
err_setup_tx:
     e1000e_reset(adapter);
 
     return err;

  这里看一下接收容器中断设置

static void e1000_configure_rx( struct e1000_adapter *adapter)
{
     struct e1000_hw *hw = &adapter->hw;
     struct e1000_ring *rx_ring = adapter->rx_ring;
     u64 rdba;
     u32 rdlen, rctl, rxcsum, ctrl_ext;
 
     if (adapter->rx_ps_pages) {
         /* this is a 32 byte descriptor */
         rdlen = rx_ring->count *
             sizeof ( union e1000_rx_desc_packet_split);
         adapter->clean_rx = e1000_clean_rx_irq_ps;
         adapter->alloc_rx_buf = e1000_alloc_rx_buffers_ps;
     } else if (adapter->netdev->mtu > ETH_FRAME_LEN + ETH_FCS_LEN) {
         rdlen = rx_ring->count * sizeof ( struct e1000_rx_desc);
         adapter->clean_rx = e1000_clean_jumbo_rx_irq;
         adapter->alloc_rx_buf = e1000_alloc_jumbo_rx_buffers;
     } else {
         rdlen = rx_ring->count * sizeof ( struct e1000_rx_desc);
         adapter->clean_rx = e1000_clean_rx_irq; 这里的函数是对前半段的一个处理流程,主要是将数据从DMA中获取然后放到队列中,供后半段进行处理。
         adapter->alloc_rx_buf = e1000_alloc_rx_buffers;
     }
 
     /* disable receives while setting up the descriptors */ //写接收控制寄存器 暂时停止接收
     rctl = er32(RCTL);
     ew32(RCTL, rctl & ~E1000_RCTL_EN);
     e1e_flush();
     msleep(10);
 
     /* set the Receive Delay Timer Register */ //设置RDTR寄存器 有关
     ew32(RDTR, adapter->rx_int_delay);
 
     /* irq moderation */ //设置RADV寄存器 有关RADV具体详见开发者手册 
     ew32(RADV, adapter->rx_abs_int_delay);
     if (adapter->itr_setting != 0)
         ew32(ITR, 1000000000 / (adapter->itr * 256));
 
     ctrl_ext = er32(CTRL_EXT);
     /* Reset delay timers after every interrupt */
     ctrl_ext |= E1000_CTRL_EXT_INT_TIMER_CLR;
     /* Auto-Mask interrupts upon ICR access */
     ctrl_ext |= E1000_CTRL_EXT_IAME;
     ew32(IAM, 0xffffffff);
     ew32(CTRL_EXT, ctrl_ext);
     e1e_flush();
 
     /*
      * Setup the HW Rx Head and Tail Descriptor Pointers and
      * the Base and Length of the Rx Descriptor Ring
      */
      //与接收描述符环有关的有4个寄存器:RDBA存放描述符缓冲的首地址 做为基地址 供64位 包括各32位的高低地址 
//RDLEN:为缓冲区分配的总空间的大小 RDH和RDT是头尾指针 存放相对基址的偏移量 RDH的值由硬件增加 表示指向下一次DMA将用的描述符
//RDT由软件增加 表示下一次要处理并送交协议栈的有关描述符
     rdba = rx_ring->dma;
     ew32(RDBAL, (rdba & DMA_BIT_MASK(32)));
     ew32(RDBAH, (rdba >> 32));
     ew32(RDLEN, rdlen);
     ew32(RDH, 0);
     ew32(RDT, 0);
     rx_ring->head = E1000_RDH;
     rx_ring->tail = E1000_RDT;
 
     /* Enable Receive Checksum Offload for TCP and UDP */
     rxcsum = er32(RXCSUM);
     if (adapter->flags & FLAG_RX_CSUM_ENABLED) {
         rxcsum |= E1000_RXCSUM_TUOFL;
 
         /*
          * IPv4 payload checksum for UDP fragments must be
          * used in conjunction with packet-split.
          */
         if (adapter->rx_ps_pages)
             rxcsum |= E1000_RXCSUM_IPPCSE;
     } else {
         rxcsum &= ~E1000_RXCSUM_TUOFL;
         /* no need to clear IPPCSE as it defaults to 0 */
     }
     ew32(RXCSUM, rxcsum);
 
     /*
      * Enable early receives on supported devices, only takes effect when
      * packet size is equal or larger than the specified value (in 8 byte
      * units), e.g. using jumbo frames when setting to E1000_ERT_2048
      */
     if ((adapter->flags & FLAG_HAS_ERT) &&
         (adapter->netdev->mtu > ETH_DATA_LEN)) {
         u32 rxdctl = er32(RXDCTL(0));
         ew32(RXDCTL(0), rxdctl | 0x3);
         ew32(ERT, E1000_ERT_2048 | (1 << 13));
         /*
          * With jumbo frames and early-receive enabled, excessive
          * C4->C2 latencies result in dropped transactions.
          */
         pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY,
                       e1000e_driver_name, 55);
     } else {
         pm_qos_update_requirement(PM_QOS_CPU_DMA_LATENCY,
                       e1000e_driver_name,
                       PM_QOS_DEFAULT_VALUE);
     }
 
     /* Enable Receives */
     ew32(RCTL, rctl);
}
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