linux-kernel - Re: [PATCH V1] arm64: dts: imx8mp: fix FEC can't work when attached to generic phy driver

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Date:   Thu, 18 Mar 2021 18:48:14 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     robh+dt@...nel.org, s.hauer@...gutronix.de, festevam@...il.com,
        kernel@...gutronix.de, linux-imx@....com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1] arm64: dts: imx8mp: fix FEC can't work when attached
 to generic phy driver

On Thu, Mar 04, 2021 at 07:40:13PM +0800, Joakim Zhang wrote:
> Some users report that FEC can't work on i.MX8MP EVK board, it brings
> inconvenience. The root cause should be FEC controller attached to
> generic phy driver, as Realtek phy driver is built as module in the
> defconfig file (CONFIG_REALTEK_PHY=m), so it is unavailable. If provide
> "reset-gpios" property, it will reset phy when probed, and no way to
> re-config phy since we use the generic phy dirver, which leads FEC can't
> work.
> 
> There are two ways to let FEC work:
> 
> 1. If you want to use generic phy dirver, please delete "reset-gpios"
> property, keep power-on strapping pins configurations.
> 
> 2. If you want to use Realtek phy driver, please buildin driver
> (CONFIG_REALTEK_PHY=y), and had better add another two reset
> properties:
> 	reset-assert-us = <20000>;
> 	reset-deassert-us = <150000>;
> According to  RTL8211 serials PHY datasheet, for a complete PHY reset,
> reset pin must be asserted low for at least 10ms for internal regulator.
> Wait for at least 72ms (for internal circuits settling time) before
> accessing the PHY register.
> 
> This patch selects method 1, since users may waste time to find out FEC
> failure, in most cases, they just want to use networking to debug other
> modules.
> 
> Fixs: commit 9e847693c6f34 ("arm64: dts: freescale: Add i.MX8MP EVK board support")
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
>  arch/arm64/boot/dts/freescale/imx8mp-evk.dts | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> index 7db4273cc88b..4f5c2fb33eda 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> @@ -97,7 +97,6 @@
>  			compatible = "ethernet-phy-ieee802.3-c22";
>  			reg = <1>;
>  			eee-broken-1000t;
> -			reset-gpios = <&gpio4 2 GPIO_ACTIVE_LOW>;

Hmm, DT is describing hardware.  If board schematic says there is
a reset GPIO, we should have it.

Shawn

>  		};
>  	};
>  };
> -- 
> 2.17.1
>