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所属分类：linux技术
GMAC网卡Fixed-Link模式
GMAC
fixed-link固定链接模式，mac与对端的连接方式是写死的，通常用于mac to mac（不排除mac to phy的情况）。内核要支持fixed-link模式，需要打开CONFIG_FIXED_PHY配置。
社区版linux的gmac网卡platform平台驱动中，在设备树默认下支持fixed-link，gmac网卡platform平台驱动默认不支持ACPI模式。
fixed-link模式的实现，概括起来就两步，
- 通过
fixed_phy_register创建phy device - 连接phy device
fixed-link的link状态通常是固定的，但也可以通过gpio GPIOF_DIR_IN寄存器获取。
设备树Fixed-Link实现
以4.19.90内核版本为例其实现方式如下（内核版本5.3之后使用phylink替代了phy lib，实现接口有所不同）：
设备树配置中定义fixed-link属性
设备树fixed-link配置
stmac驱动实现，of_phy_register_fixed_link函数读取设备树fixed-link属性并通过fixed_phy_register创建phy device，of_phy_connect连接phy device。
stmmac_platform.c: static int stmmac_dt_phy(struct plat_stmmacenet_data *plat, struct device_node *np, struct device *dev) { ... ... /* If phy-handle is not specified, check if we have a fixed-phy */ if (!plat->phy_node && of_phy_is_fixed_link(np)) { if ((of_phy_register_fixed_link(np) < 0)) return -ENODEV; dev_dbg(dev, "Found fixed-link subnoden"); plat->phy_node = of_node_get(np); mdio = false; } ... ... } stmmac_main.c: static int stmmac_init_phy(struct net_device *dev) { ... ... if (priv->plat->phy_node) { phydev = of_phy_connect(dev, priv->plat->phy_node, &stmmac_adjust_link, 0, interface); ... ... }通过of_phy_register_fixed_link函数可知，fixed-link的配置方式不只一种。
/drivers/of/of_mdio.c: int of_phy_register_fixed_link(struct device_node *np) { struct fixed_phy_status status = {}; struct device_node *fixed_link_node; u32 fixed_link_prop[5]; const char *managed; int link_gpio = -1; if (of_property_read_string(np, "managed", &managed) == 0 && strcmp(managed, "in-band-status") == 0) { /* status is zeroed, namely its .link member */ goto register_phy; } /* New binding */ fixed_link_node = of_get_child_by_name(np, "fixed-link"); if (fixed_link_node) { status.link = 1; status.duplex = of_property_read_bool(fixed_link_node, "full-duplex"); if (of_property_read_u32(fixed_link_node, "speed", &status.speed)) { of_node_put(fixed_link_node); return -EINVAL; } status.pause = of_property_read_bool(fixed_link_node, "pause"); status.asym_pause = of_property_read_bool(fixed_link_node, "asym-pause"); link_gpio = of_get_named_gpio_flags(fixed_link_node, "link-gpios", 0, NULL); of_node_put(fixed_link_node); if (link_gpio == -EPROBE_DEFER) return -EPROBE_DEFER; goto register_phy; } /* Old binding */ if (of_property_read_u32_array(np, "fixed-link", fixed_link_prop, ARRAY_SIZE(fixed_link_prop)) == 0) { status.link = 1; status.duplex = fixed_link_prop[1]; status.speed = fixed_link_prop[2]; status.pause = fixed_link_prop[3]; status.asym_pause = fixed_link_prop[4]; goto register_phy; } return -ENODEV; register_phy: return PTR_ERR_OR_ZERO(fixed_phy_register(PHY_POLL, &status, link_gpio, np)); } EXPORT_SYMBOL(of_phy_register_fixed_link);ACPI Fixed-Link实现
本质上ACPI和设备树fixed-link实现是一致的，只是部分接口函数不同，ACPI下可以使用phy_connect_direct进行连接（5.3之后的内核版本使用phylink模式，连接函数是phylink_connect_phy）。
stmmac_platform.c: int fw_phy_register_fixed_link(struct fwnode_handle *np, struct plat_stmmacenet_data *plat) { struct fixed_phy_status status = {}; u32 fixed_link_prop[5]; int size = 5, err; int link_gpio = -1; struct phy_device *phydev = NULL; if (FORCE_FIXED_LINK) { status.link = 1; status.duplex = DUPLEX_FULL; status.speed = SPEED_1000; pr_info("force fixed-link busid %dn", plat->bus_id); } else { err = fwnode_property_read_u32_array(np, "fixed-link", fixed_link_prop, size); if (err) { pr_err("----there is no fixed-link property in DSD--n"); return 0; } status.link = 1; status.duplex = fixed_link_prop[1]; status.speed = fixed_link_prop[2]; status.pause = fixed_link_prop[3]; status.asym_pause = fixed_link_prop[4]; } phydev = fixed_phy_register(PHY_POLL, &status, link_gpio, 0); if (IS_ERR(phydev)) { pr_err("fixed_phy_register failedn"); return -1; } plat->fixedphydev = phydev; return 0; } stmmac_main.c: static int stmmac_init_phy(struct net_device *dev) { ... ... if (priv->plat->fixedphydev) { phydev = priv->plat->fixedphydev; if (phy_connect_direct(dev, phydev, &stmmac_adjust_link, interface)) { netdev_err(priv->dev, "phy_connect_direct failedn"); phydev = NULL; } ... ... }
