[参考译文] TDA4VM-Q1：DSA KSZ9477/9896 开关 CPSW RGMII 问题

Other Parts Discussed in Thread: TDA4VM

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1590441/tda4vm-q1-dsa-ksz9477-9896-switch-issues-with-cpsw-rgmii

器件型号： TDA4VM-Q1
Thread： TDA4VM 中讨论的其他器件

您好：

这是上一篇文章的后续文章[1]。

我将在定制电路板上使用 J721e/TDA4VM SoC、当时 MCU_CPSW 接口连接到 ksz9896 外部开关。

在我们确定 CPSW 和 KSZ 驱动器都增加了 2ns 的 RGMII 延迟之前、我们在 iperf 测试中遇到了多个问题。

TI 不会在没有 TX 延迟的情况下测试 CPSW 器件、但我们可以从器件树中自定义 ksz 延迟。 因此、修复方法是禁用（设置为 0）“rx-internal-delay-ps"。“。

以下是我们的器件树片段（内核 6.1.y）：

/* mcu domain */
&mcu_cpsw {
    status = "okay";
    [...]
};

/* mcu domain */
&davinci_mdio {
	status = "disabled";
	/* KSZ9896C                                           */
	/* NO mdio link since we are using the SPI interface! */
};

/* mcu domain */
&cpsw_port1 {
	status = "okay";
	/* The PCB does not add RGMII rx/tx delays via extra long data/clock
	 * traces, so 'rgmii-id' should be used.
	 * When rgmii-id is used, TI fixup to rgmii-rxid:
	 * dmesg: "am65-cpsw-nuss eth0: configuring for fixed/rgmii-rxid link mode"
	 * See: lore.kernel.org/.../54d6cd05-65ef-4e1d-8041-3e4a2c50b443@ti.com
	 */
	phy-mode = "rgmii-id";
	fixed-link {
		speed = <1000>;
		full-duplex;
	};
};

&mcu_spi0 {
    status = "okay";

    /* switch Ethernet */
    switch@0 {

        [...]

        port@5 {
            reg = <5>;
            ethernet = <&mcu_cpsw>;
            phy-mode = "rgmii-id";
            /* ksz_parse_rgmii_delay() set tx_delay to 2 nsec by default
            * We explicitely set the default delay here.
            */
            tx-internal-delay-ps = <2000>;
            /* The CPSW will already put a 2 nsec delay between clock and data,
            * disable the 2 nsec delay added by ksz_parse_rgmii_delay().
            */
            rx-internal-delay-ps = <0>;

            fixed-link {
                speed = <1000>;
                full-duplex;
            };
        };
    };
};

[1] https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1428274/sk-am64b-ksz9477-switch-not-working-with-cpsw-rgmii
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/net/dsa/microchip/ksz_common.c?h=v6.1.158#n2857

此致、
罗曼语