Re: [PATCH v2 06/10] net: pcs: xpcs: add ANRESTART support for SGMII link recovery

From: Coia Prant <coiaprant@gmail.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Heiko Stuebner <heiko@sntech.de>, Vinod Koul <vkoul@kernel.org>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Romain Gantois <romain.gantois@bootlin.com>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Russell King <linux@armlinux.org.uk>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	David Heidelberg <david@ixit.cz>,
	netdev@vger.kernel.org, linux-rockchip@lists.infradead.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-renesas-soc@vger.kernel.org,
	Jiawen Wu <jiawenwu@trustnetic.com>
Subject: Re: [PATCH v2 06/10] net: pcs: xpcs: add ANRESTART support for SGMII link recovery
Date: Mon, 03 Aug 2026 02:25:45 +0800	[thread overview]
Message-ID: <2E676CD9-82F3-404A-B24D-27679042783B@gmail.com> (raw)
In-Reply-To: <2886b24e-1c3d-48f7-8b22-9620fa0404f7@lunn.ch>

On August 2, 2026 10:30:52 PM GMT+08:00, Andrew Lunn <andrew@lunn.ch> wrote:
>On Sun, Aug 02, 2026 at 11:11:40AM +0800, Coia Prant wrote:
>> Hi Andrew,
>> 
>> Thanks for the careful review.
>> 
>> > This probably needs more wide spread testing. I would be afraid that
>> > if you kick off an AN cycle, you loose the link until it completes?
>> > You would of noticed that on your hardware, but other hardware
>> > obviously behaves differently...
>> 
>> The trigger condition is: link is down AND an_complete is set.
>
>Ah, i missed the "link is down" check. That makes it safer.
>
>I still find it interesting that this devices is different. Has the
>silicon vendor done the integration of the licensed IP wrong?
>
>> Regarding testing:
>> - Jiawen Wu has tested this on Wangxun NICs and reported no regression
>>   (Tested-by tag included in the patch).
>
>Probably Maxime will test on the platform he has, but i don't know if
>any use the XPCS.
>
>	Andrew

Hi Andrew,

Thanks for the follow-up.

Honestly, I'm not sure why the RK3568 XPCS behaves this way. I don't have
other DW XPCS hardware to compare against, so I can't say whether this is
a silicon integration quirk or something else.

What I can confirm is that on RK3568, the PCS does not restart AN
automatically when the link drops and comes back. Without this ANRESTART
change, the link stays dead forever.

I agree that wider testing is needed. If Maxime or anyone else finds a
regression on other hardware, we can revisit and condition it with a
platform-specific flag. For now, the change is limited to the SGMII
recovery path with a safe condition (link down + an_complete), so the
risk should be minimal.

Thanks,
Coia

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