linux-kernel - Re: [PATCH net-next v3 3/6] net: hisilicon: add support for hisi

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Date: Tue, 20 Feb 2024 06:34:18 +0800
From: Yang Xiwen <forbidden405@...look.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Yisen Zhuang <yisen.zhuang@...wei.com>,
 Salil Mehta <salil.mehta@...wei.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v3 3/6] net: hisilicon: add support for
 hisi_femac core on Hi3798MV200

On 2/20/2024 6:05 AM, Andrew Lunn wrote:
>> It's not MAC which behaves wrongly, it's the MDIO bus. If we don't follow
>> the reset procedure properly. The MDIO bus fails to respond to any
>> write/read commands. But i believe MAC controller and PHY are still working.
>> I recalled that it can still transfer network packets, though it fails to
>> read PHY registers from MDIO bus so only 10Mbps is available (And the phy id
>> read out is always 0x0, normally it's 0x20669853).
>>
>> Maybe during initialization, PHY sent some garbage to MDIO bus and killed
>> it.
> MDIO bus masters are really simple things, not much more than a shift
> register. I find it hard to believe the MDIO bus master breaks because
I conclude that master side is working. Because when i tried to read PHY 
registers manually. It does say it completes reading(the finish bit is 
set). Though the data read out is invalid.
> of reset order. If the MDIO pins went to SoC pins, it would be simple
> to prove, a bus-pirate or similar can capture the signals and sigrok
> can decode MDIO.
>
> To me, its more likely the PHY side of the MDIO bus is broken somehow.
>
>     Andrew

-- 
Regards,
Yang Xiwen