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

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Message-ID: <DB8PR04MB6795178A70C52D067DC1AEE1E6699@DB8PR04MB6795.eurprd04.prod.outlook.com>
Date:   Thu, 18 Mar 2021 11:03:59 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Shawn Guo <shawnguo@...nel.org>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V1] arm64: dts: imx8mp: fix FEC can't work when attached
 to generic phy driver


> -----Original Message-----
> From: Shawn Guo <shawnguo@...nel.org>
> Sent: 2021年3月18日 18:48
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: robh+dt@...nel.org; s.hauer@...gutronix.de; festevam@...il.com;
> kernel@...gutronix.de; dl-linux-imx <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.

Hi Shawn,

Seems you prefer to 2, is it possible to buildin Realtek PHY(CONFIG_REALTEK_PHY=y)? If not, it is going to be tricky.

Best Regards,
Joakim Zhang
> Shawn
> 
> >  		};
> >  	};
> >  };
> > --
> > 2.17.1
> >