STMicro ethernet driver note

Source File and Config

stmmac source code files introduction.

interface to upper layer:

  • stmmac_main.o: stmmac_netdev_ops

  • stmmac_ethtool.o: stmmac_ethtool_ops

internal operations:

  • dwmac: stmmac_ops, stmmac_dma_ops

    • dwmac_lib.o

    • dwmac1000: dwmac1000_core.o dwmac1000_dma.o

    • dwmac100: dwmac100_core.o dwmac100_dma.o

  • norm_desc.o, enh_desc.o: dma descriptor, stmmac_desc_ops

  • ring_mode.o, chain_mode.o: stmmac_mode_ops

  • other: stmmac_mdio.o, mmc_core.o, stmmac_hwtstamp.o, stmmac_ptp.o

Kconfig options:

  • bus: stmmac_pci.c | stmmac_platform.c

    • stmmac_platform.c (struct platform_driver stmmac_pltfr_driver)

  • dwmac: dwmac-meson.c | dwmac-sunxi.c | dwmac-sti.c

header files

  • stmmac.h, common.h

  • descs.h, descs_com.h (dma descriptor)

  • dwmac100.h, dwmac1000.h, dwmac_dma.h

  • am_eth_reg.h, mmc.h, stmmac_ptp.h

Data Structure

4 ops in mac_device_info:

struct mac_device_info

- stmmac_ops *mac;       // dwmac*.c
- stmmac_dma_ops *dma;   // dwmac*.c
- stmmac_desc_ops *desc; // *_desc.c
- stmmac_mode_ops *mode; // *_mode.c

e.g. priv->hw->mac->set_umac_addr()
use stmmac_ops dwmac1000_ops->set_umac_addr() at dwmac1000_core.c

struct stmmac_priv, which is stmmac’s private_data of netdev.:

void __iomem* ioaddr;              // MMIO region base address
struct mac_device_info* hw;        // 4 ops

struct plat_stmmacenet_data* plat; // struct device->platform_data

Control Flow

stmmac driver setting mac address

// in stmmac_main.c
stmmac_hw_setup()
=> priv->hw->mac->set_umac_addr() = dwmac1000_ops.set_umac_addr() = dwmac1000_set_umac_addr()
=> stmmac_set_mac_addr()

stmmac MMIO region

以下以 stmmac_set_mac_addr() 使用到的 MMIO region 為例子

1. MMIO region 透過 platform_get_resource() 得到, 並透過 ioremap() 轉成 virtual address 給 driver 使用.

// driver use MMIO region by accessing priv->ioaddr
stmmac_pltfr_probe(struct platform_device *pdev)

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    addr = devm_ioremap_resource(dev, res);
    ...
    stmmac_dvr_probe(..., void __iomem *addr)

        priv->ioaddr = addr;

2. platform_get_resource() 透過 device tree 獲得 hard-coded 的 MMIO region address. platform_device 適用這套 API.

// platform_get_resource() get resource from Device Tree
// in arch/arm64/boot/dts/meson64_odroidc2.dts

    ethmac: ethernet@0xc9410000{
         compatible = "amlogic, gxbb-rgmii-dwmac";
         reg = <0x0 0xc9410000 0x0 0x10000
         0x0 0xc8834540 0x0 0x8>
         ...
    }
    platform_get_resource(pdev, IORESOURCE_MEM, 0): start=0xc9410000, size=0x10000
    platform_get_resource(pdev, IORESOURCE_MEM, 1): start=0xc8834540, size=0x8

p.s. stmmac_set_mac_addr() 計算 MMIO offset 的方式

// MMIO offset
// in dwmac1000.h
GMAC_ADDR_HIGH(reg) = 0x40 + reg*8 if reg <= 15;
GMAC_ADDR_LOW(reg)  = 0x44 + reg*8 if reg <= 15;

net_device_ops/NAPI transfer and receive

driver transfer data to device.

ndo_start_xmit()

receive data from parameter sk_buff and transfer to dma_desc?

  • data:

    priv->cur_tx
priv->dma_tx[entry].des2: dma_map_single(), skb_frag_dma_map()
priv->tx_skbuff_dma[entry].buf: alias of priv->dma_tx[entry].des2
priv->tx_skbuff[entry]

  • functions:

    priv->hw->dma ops: enable_dma_transmission(priv->ioaddr);
priv->hw->desc ops: prepare_tx_desc(), set_tx_owner(), close_tx_desc()
skb_frag_dma_map(): dma_map_page() from ``sk_buff's`` page.

所以, 有幾個重點的 dependency 先處理

  1. dma mapping API: dma_map_single(), dma_map_page()

  2. sk_buff intro:

  3. stmmac hw datasheet? 我想看 TX/RX Ring 的 data structure

driver receive data from device.

stmmac_poll()

other net_device_ops

  • ndo_ioctl

    • stmmac_hwtstamp_ioctl()

    • phy_mii_ioctl(): forward to PHY ioctl()

  • ndo_open, ndo_stop

  • ndo_poll_controller

  • ndo_tx_timeout: stmmac_tx_err(priv);

  • ndo_set_config: not supported (-EOPNOTSUPP)

  • ndo_set_mac_address = NULL

  • ndo_change_mtu: dev->mtu = new_mtu; netdev_update_features(dev);

  • ndo_fix_features: check flags

  • ndo_set_rx_mode: priv->hw->mac->set_filter(dev, priv->synopsys_id);

more than net_device_ops, recieve need interrupt

  • stmmac_interrupt() => stmmac_dma_interrupt(): 應該是 interrupt handler

    • priv->hw->dma->dma_interrupt() 確認是否 handle_tx/rx, 或者 transmit error. (handle_tx/rx 對應到 dwmac DMA 的 normal interrupt 的其中兩個種類)

    • 如果需要 handle_tx/rx, 則 trigger __napi_schedule()

Other Info

platform bus abstraction

stmmac_platform.c implement a platform driver stmmac_pltfr_driver. This driver is a wrapper of stmmac_driver.

stmmac_main.c registers this platform driver (stmmac_pltfr_driver) at kernel module initialization.

stmmac_pltfr_driver implements platform driver ops (ops of struct platform_driver), like probe, remove, driver.shutdown, driver.pm_ops. stmmac_pltfr_driver’s ops depend on stmmac_driver ops, just do some customization.

customizations:

  • MMIO region: platform_get_resource(), ioremap()

  • 3 IRQs:

    priv->dev->irq = platform_get_irq_byname(pdev, "macirq");
priv->wol_irq = platform_get_irq_byname(pdev, "eth_wake_irq");
priv->lpi_irq = platform_get_irq_byname(pdev, "eth_lpi");

  • struct device’s platform_data

    • stmmac_probe_config_dt()

      • platdata_copy_from_machine_data(device, plat);

      • setup_mac_addr(pdev, mac);

    • plat_stmmacenet_data->setup()

    • plat_stmmacenet_data->init()

dwmac-meson.c

implements 2 functions setup() and fix_mac_speed()

setup functions to device’s platform_data plat_stmmacenet_data:

platdata_copy_from_machine_data(const struct of_device_id *device, struct plat_stmmacenet_data *plat){
    if (device->data) {
        const struct stmmac_of_data *data = device->data;
        plat->setup = data->setup;
        plat->fix_mac_speed = data->fix_mac_speed;
        ...
    }
}

usage about these functions:

1. priv->plat->fix_mac_speed()
2. custom setup function in platform_driver initialization.

stmmac_pltfr_probe() => stmmac_probe_config_dt() => platdata_copy_from_machine_data()
    struct platform_device *pdev;
    struct plat_stmmacenet_data *plat_dat = dev_get_platdata(&pdev->dev);
    ...
    // custom setup function
    plat_dat->setup()

dwmac DMA

  • source codes: dwmac_lib.c, dwmac_dma.h

  • DMA registers

    • CSR: control and status registers.

    • dwmac_dma.h: DMA CSR Mapping(MMIO), from DMA_BUS_MODE(0x1000) to DMA_HW_FEATURE(0x1058). (CSR0 to CSR8, and … CSR?)

    • CSR1: enable dma transmission

    • CSR7: mask interrupt and record interrupt type. (DMA_INTR_ENA_*)

    • DMA status register (CSR5): DMA_STATUS_*

    • DMA control register (CSR6): DMA_CONTROL_*

  • DMA interrupt: DMA_INTR_ENA_*

    • normal interrupt: 5 kinds, from NIE to ERE

    • abnormal interrupt: 10 kinds, from AIE to TSE