rk3399 stmmac驱动解析

RK3399是一款由Rockchip公司生产的64位六核处理器，它集成了双千兆以太网MAC控制器。在RK3399的Linux内核中，提供了对该以太网控制器的stmmac驱动程序支持。以下是对RK3399 stmmac驱动程序的解析：

1. 设备树绑定

RK3399的设备树文件中需要进行stmmac驱动程序的绑定。在设备树中需要指定MAC地址、PHY地址、中断控制器、中断号等信息。以下是设备树中stmmac驱动程序的绑定示例：

&mac {
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&mac_rgmii_pins>, <&mac_clk_rx_pins>, <&mac_clk_tx_pins>;
    phy-mode = "rgmii";
    phy-handle = <&phy0>;
    phy0: ethernet-phy@0 {
        reg = <0>;
        compatible = "ethernet-phy-ieee802.3-c22";
    };
    interrupts = <GIC_SPI 123 IRQ_TYPE_LEVEL_HIGH>;
    interrupt-names = "macirq";
    local-mac-address = [XX XX XX XX XX XX];
};

2. 驱动程序初始化

在驱动程序初始化时，需要进行一些基本的设置，如设置MAC地址、中断处理程序、DMA通道等。以下是RK3399 stmmac驱动程序初始化的代码示例：

static int rk3399_stmmac_probe(struct platform_device *pdev)
{
    struct rk_priv_data *bsp_priv;
    struct stmmac_resources stmmac_res;
    int ret;

    /* Allocate bsp_priv */
    bsp_priv = devm_kzalloc(&pdev->dev, sizeof(struct rk_priv_data), GFP_KERNEL);
    if (!bsp_priv)
        return -ENOMEM;

    /* Get GPIO reset pin */
    bsp_priv->reset_gpio = of_get_named_gpio(pdev->dev.of_node, "reset-gpios", 0);
    if (gpio_is_valid(bsp_priv->reset_gpio)) {
        ret = devm_gpio_request_one(&pdev->dev, bsp_priv->reset_gpio, GPIOF_OUT_INIT_LOW, "stmmac_reset");
        if (ret) {
            dev_err(&pdev->dev, "Failed to request GPIO reset pin %d: %d\n",
                    bsp_priv->reset_gpio, ret);
            goto err_out;
        }
    }

    /* Set MAC address */
    stmmac_res.mac_addr = bsp_priv->mac_addr;

    /* Set IRQ handler */
    stmmac_res.irq = platform_get_irq(pdev, 0);
    stmmac_res.irqflags = IRQF_TRIGGER_LOW;
    stmmac_res.irqhandler = rk3399_stmmac_isr;

    /* Set DMA channel */
    stmmac_res.dma_rx_channel = dma_request_slave_channel(&pdev->dev, "rx");
    stmmac_res.dma_tx_channel = dma_request_slave_channel(&pdev->dev, "tx");

    /* Initialize stmmac */
    ret = stmmac_dvr_probe(&pdev->dev, &stmmac_res, &rk3399_pdata, &bsp_priv->plat_dat);
    if (ret)
        goto err_out;

    return 0;

err_out:
    return ret;
}

3. DMA传输

RK3399 stmmac驱动程序使用DMA引擎来实现高速数据传输。在DMA传输开始前，需要配置DMA通道和缓冲区。以下是RK3399 stmmac驱动程序DMA传输的代码示例：

static int rk3399_stmmac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
{
    struct rk_priv_data *bsp_priv = netdev_priv(ndev);
    struct stmmac_xgmac_dma_ops *dma_ops = &bsp_priv->plat_dat->dma_ops;
    struct stmmac_packet_attrs attrs;
    dma_addr_t dma_addr;
    int ret;

    /* Configure DMA buffer */
    skb->ip_summed = CHECKSUM_NONE;
    skb_push(skb, 2);
    skb->data[0] = 0;
    skb->data[1] = 0;

    /* Configure DMA attributes */
    attrs.tci = 0;
    attrs.proto = 0;
    attrs.dma_desc = NULL;
    attrs.tx_csum = 0;
    attrs.tx_timestamp = 0;
    attrs.tx_vlan = 0;
    attrs.tx_vlan_cfi = 0;

    /* Map DMA buffer */
    dma_addr = dma_map_single(&pdev->dev, skb->data, skb->len, DMA_TO_DEVICE);
    if (dma_mapping_error(&pdev->dev, dma_addr)) {
        dev_err(&pdev->dev, "Failed to map DMA buffer\n");
        goto err_out;
    }

    /* Configure DMA descriptor */
    dma_ops->tx_dma_desc_init(ndev, &attrs, dma_addr, skb->len, 0);

    /* Start DMA transfer */
    ret = dma_ops->tx_dma(ndev, &attrs);
    if (ret) {
        dev_err(&pdev->dev, "Failed to start DMA transfer\n");
        dma_unmap_single(&pdev->dev, dma_addr, skb->len, DMA_TO_DEVICE);
        goto err_out;
    }

    return NETDEV_TX_OK;

err_out:
    dev_kfree_skb(skb);
    return NETDEV_TX_OK;
}

总的来说，RK3399 stmmac驱动程序是一个功能完善、性能优越的以太网驱动程序，它使用了DMA引擎来实现高速数据传输。通过对设备树进行绑定和执行初始化，可以使该驱动程序在RK3399平台上正常工作。