linux-kernel - Re: [PATCH 3/7] arm64: dts: imx8mp-venice-gw702x: reduce RGMII CLK drive strength

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Message-ID: <20250918091023.GC23028@nxa18884-linux.ap.freescale.net>
Date: Thu, 18 Sep 2025 17:10:23 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Tim Harvey <tharvey@...eworks.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] arm64: dts: imx8mp-venice-gw702x: reduce RGMII CLK
 drive strength

Hi Tim,

On Tue, Sep 16, 2025 at 08:32:12AM -0700, Tim Harvey wrote:
>The i.MX8M Plus EQOS RGMII tracelength is less than 1in and does not
>require a x6 drive strength. Reduce the CLK drive strength to x1 for
>better emissions.
>
>Signed-off-by: Tim Harvey <tharvey@...eworks.com>
>---
> arch/arm64/boot/dts/freescale/imx8mp-venice-gw702x.dtsi | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/arm64/boot/dts/freescale/imx8mp-venice-gw702x.dtsi b/arch/arm64/boot/dts/freescale/imx8mp-venice-gw702x.dtsi
>index a1232a4f8485..dd9eeb3479fd 100644
>--- a/arch/arm64/boot/dts/freescale/imx8mp-venice-gw702x.dtsi
>+++ b/arch/arm64/boot/dts/freescale/imx8mp-venice-gw702x.dtsi
>@@ -462,7 +462,7 @@ MX8MP_IOMUXC_ENET_TD1__ENET_QOS_RGMII_TD1		0x16
> 			MX8MP_IOMUXC_ENET_TD2__ENET_QOS_RGMII_TD2		0x16
> 			MX8MP_IOMUXC_ENET_TD3__ENET_QOS_RGMII_TD3		0x16
> 			MX8MP_IOMUXC_ENET_TX_CTL__ENET_QOS_RGMII_TX_CTL		0x16
>-			MX8MP_IOMUXC_ENET_TXC__CCM_ENET_QOS_CLOCK_GENERATE_TX_CLK	0x16
>+			MX8MP_IOMUXC_ENET_TXC__CCM_ENET_QOS_CLOCK_GENERATE_TX_CLK	0x0

You also changed FSEL from 2 to 0. So I would add this in commit that if this
matches:
Since TXC is not a high frequency clock, use slow slew rate for lower emissions
and better signal quality

Regards
Peng
> 		>;
> 	};
> 
>-- 
>2.25.1
>