The Ethernet TX performance has been historically bad on Meson8b and Meson8m2 SoCs because high packet loss was seen. I found out that this was related (yet again) to the RGMII TX delay configuration. In the process of discussing the big picture (and not just a single patch) [0] with Andrew I discovered that the IP block behind the dwmac-meson8b driver actually seems to support the configuration of the RGMII RX delay (at least on the Meson8b SoC generation). Since I sent the last RFC I got additional documentation from Jianxin (many thanks!). Also I have discovered some more interesting details: - Meson8b Odroid-C1 requires an RX delay (by either the PHY or the MAC) Based on the vendor u-boot code (not upstream) I assume that it will be the same for all Meson8b and Meson8m2 boards - Khadas VIM2 seems to have the RX delay built into the PCB trace length. When I enable the RX delay on the PHY or MAC I can't get any data through. I expect that we will have the same situation on all GXBB, GXM, AXG, G12A, G12B and SM1 boards Changes since RFC v1 at [1]: - add support for the timing adjustment clock input (dt-bindings and in the driver) thanks to the input from the unnamed Ethernet engineer at Amlogic. This is the missing link between the fclk_div2 clock and the Ethernet controller on Meson8b (no traffic would flow if that clock was disabled) - add support fot the amlogic,rx-delay-ns property. The only supported values so far are 0ns and 2ns. The registers seem to allow more precise timing adjustments, but I could not make that work so far. - add more register documentation (for the new RX delay bits) and unified the placement of existing register documentation. Again, thanks to Jianxin and the unnamed Ethernet engineer at Amlogic - DO NOT MERGE: .dts patches to show the conversion of the Meson8b and Meson8m2 boards to "rgmii-id". I didn't have time for all arm64 patches yet, but these will switch to phy-mode = "rgmii-txid" with amlogic,rx-delay-ns = <0> (because the delay seems to be provided by the PCB trace length). [0] https://patchwork.kernel.org/patch/11309891/ [1] https://patchwork.kernel.org/cover/11310719/ Martin Blumenstingl (11): dt-bindings: net: meson-dwmac: Add the amlogic,rx-delay-ns property dt-bindings: net: dwmac-meson: Document the "timing-adjustment" clock net: stmmac: dwmac-meson8b: use FIELD_PREP instead of open-coding it net: stmmac: dwmac-meson8b: Move the documentation for the TX delay net: stmmac: dwmac-meson8b: Add the PRG_ETH0_ADJ_* bits net: stmmac: dwmac-meson8b: Fetch the "timing-adjustment" clock net: stmmac: dwmac-meson8b: Make the clock enabling code re-usable net: stmmac: dwmac-meson8b: add support for the RX delay configuration arm64: dts: amlogic: Add the Ethernet "timing-adjustment" clock ARM: dts: meson: Add the Ethernet "timing-adjustment" clock ARM: dts: meson: Switch existing boards with RGMII PHY to "rgmii-id" .../bindings/net/amlogic,meson-dwmac.yaml | 23 ++- arch/arm/boot/dts/meson8b-odroidc1.dts | 3 +- arch/arm/boot/dts/meson8b.dtsi | 5 +- arch/arm/boot/dts/meson8m2-mxiii-plus.dts | 4 +- arch/arm/boot/dts/meson8m2.dtsi | 5 +- arch/arm64/boot/dts/amlogic/meson-axg.dtsi | 6 +- .../boot/dts/amlogic/meson-g12-common.dtsi | 6 +- arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi | 5 +- arch/arm64/boot/dts/amlogic/meson-gxl.dtsi | 5 +- .../ethernet/stmicro/stmmac/dwmac-meson8b.c | 140 ++++++++++++++---- 10 files changed, 150 insertions(+), 52 deletions(-) -- 2.26.2
