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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Neil Armstrong , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Maxime Chevallier , Maxime Coquelin , Alexandre Torgue Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH v2 1/7] net: stmmac: dwmac-meson8b: let the controller apply the RGMII delays Date: Wed, 7 Oct 2026 09:26:21 +0100 Message-ID: <20261007082627.63807-2-tanure@linux.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261007082627.63807-1-tanure@linux.com> References: <20261007082627.63807-1-tanure@linux.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit RGMII needs a delay on each of its two clocks. A board can get it from the length of its tracks, from the PHY, or from the controller. "rgmii-id" in the device tree says the delay is added inside the chips but not which chip adds it, and the generic tx-internal-delay-ps and rx-internal-delay-ps properties name the controller. This driver ignored those properties. In the "-id" modes it switched its own delays off and left the whole job to the PHY, so a board that asks the controller for one of them does not get it, and a board whose PHY cannot supply that delay has no usable link at all. Boards not using those properties behave as before. Assisted-by: LLM Signed-off-by: Lucas Tanure --- .../ethernet/stmicro/stmmac/dwmac-meson8b.c | 46 ++++++++++++++++++- 1 file changed, 44 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c index e4d5c41294f4..d73dfd0ac167 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c @@ -92,6 +92,8 @@ struct meson8b_dwmac { struct clk *rgmii_tx_clk; u32 tx_delay_ns; u32 rx_delay_ps; + bool mac_tx_delay; + bool mac_rx_delay; struct clk *timing_adj_clk; }; @@ -299,6 +301,22 @@ static int meson8b_init_rgmii_delays(struct meson8b_dwmac *dwmac) delay_config = rx_adj_config; break; case PHY_INTERFACE_MODE_RGMII_ID: + /* + * "rgmii-id" only says the delays are internal, not which + * side applies them. The *-internal-delay-ps properties say + * it is this controller, so leave ours switched on. + */ + if (dwmac->mac_tx_delay || dwmac->mac_rx_delay) { + delay_config = 0; + if (dwmac->mac_tx_delay) + delay_config |= tx_dly_config; + if (dwmac->mac_rx_delay) + delay_config |= rx_adj_config; + else + cfg_rxclk_dly = 0; + break; + } + fallthrough; case PHY_INTERFACE_MODE_RMII: delay_config = 0; cfg_rxclk_dly = 0; @@ -384,6 +402,7 @@ static int meson8b_dwmac_probe(struct platform_device *pdev) struct plat_stmmacenet_data *plat_dat; struct stmmac_resources stmmac_res; struct meson8b_dwmac *dwmac; + u32 tx_delay_ps; int ret; ret = stmmac_get_platform_resources(pdev, &stmmac_res); @@ -409,9 +428,13 @@ static int meson8b_dwmac_probe(struct platform_device *pdev) dwmac->dev = &pdev->dev; dwmac->phy_mode = plat_dat->phy_interface; + /* the generic property is preferred over the vendor one */ + if (!of_property_read_u32(pdev->dev.of_node, "tx-internal-delay-ps", + &tx_delay_ps)) + dwmac->tx_delay_ns = tx_delay_ps / 1000; /* use 2ns as fallback since this value was previously hardcoded */ - if (of_property_read_u32(pdev->dev.of_node, "amlogic,tx-delay-ns", - &dwmac->tx_delay_ns)) + else if (of_property_read_u32(pdev->dev.of_node, "amlogic,tx-delay-ns", + &dwmac->tx_delay_ns)) dwmac->tx_delay_ns = 2; /* RX delay defaults to 0ps since this is what many boards use */ @@ -424,6 +447,25 @@ static int meson8b_dwmac_probe(struct platform_device *pdev) dwmac->rx_delay_ps *= 1000; } + /* + * Each property names one clock this controller delays itself. The + * PHY must be asked for whatever is left, or the two would delay the + * same clock and push it past the window. + */ + dwmac->mac_tx_delay = of_property_present(pdev->dev.of_node, + "tx-internal-delay-ps"); + dwmac->mac_rx_delay = of_property_present(pdev->dev.of_node, + "rx-internal-delay-ps"); + + if (dwmac->phy_mode == PHY_INTERFACE_MODE_RGMII_ID) { + if (dwmac->mac_tx_delay && dwmac->mac_rx_delay) + plat_dat->phy_interface = PHY_INTERFACE_MODE_RGMII; + else if (dwmac->mac_tx_delay) + plat_dat->phy_interface = PHY_INTERFACE_MODE_RGMII_RXID; + else if (dwmac->mac_rx_delay) + plat_dat->phy_interface = PHY_INTERFACE_MODE_RGMII_TXID; + } + if (dwmac->data->has_prg_eth1_rgmii_rx_delay) { if (dwmac->rx_delay_ps > 3000 || dwmac->rx_delay_ps % 200) { dev_err(dwmac->dev, -- 2.56.0