From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D05D933ADAD for ; Mon, 17 Nov 2025 15:24:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763393052; cv=none; b=kVI/teBndpA1ELC6+/pNpPtDkMR1YQ87P0gIZIbSGnmRXExjP4aKJkvvABuD8uLjHLYyEOqW2GL/Duu2KkIrq7dLs5ni/DYq4DNTuPvGSYBduOslRUPU7FG+AOal/hlQmMMs7JRD9Nk+uAZEYGUmor06Rh//TqcaytvM8AM7opg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763393052; c=relaxed/simple; bh=nImvHgHuh8U26+QS6hPu+na/IKrfgHgn7vvEmmjh7Wc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sc3R885KBy2ASqgHWk5O15GrKopRg3CtUhP6Rno4xmBrcefH17/68pFgvRIEhAeFcJFYc5Ypvzb7RUygqerRpt8kQ/aFy7+uRWXLOQ7coMegM3aZ4dSwZBu6qEu0jQThZKuQHbARlXjM89bt9BcuWND3mSS93/VIQqZcen1WUDk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=1IKduW8G; arc=none smtp.client-ip=185.171.202.116 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="1IKduW8G" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 14223C1265B; Mon, 17 Nov 2025 15:23:45 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 25D71606B9; Mon, 17 Nov 2025 15:24:07 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 5115510371D02; Mon, 17 Nov 2025 16:24:02 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1763393046; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=TiJUeO+1mFIQ8q0hDazDlQagCI2bQhPorMuM+JhSBt0=; b=1IKduW8GwGYQRbLYRwwSK2q2dN3ei2wB4vn92P9PoiTdzpvdR2+izoDNUrb2UmzJpLelGa BanXTbQvSbmDQmwgrpgnAA/VmGZrFfd6brJBfqw+jXbebOqP8eR7BLhtSBQYy1jmNdrLIw 8+CAQuFsaw6YxN++hEyUzl5+mgxZPJ3e+sv9lgUqOei+xiG9TZ/90g2zZasx1ujTiVwLhE F7XwRP0nOsmGlTpCosM7oEhXmkeE248b3s1AMAppn6Yx2QrCp0KhN7tPlHb1hI3k/Nyn+K JqQXjIA5Szax0eIDY9KzUzD90FqGB48hu93sXIdzUj3oa0NcxVuQ9C3o0JZN8w== Message-ID: <0baed1d4-65f0-409e-8284-d6af44bf7beb@bootlin.com> Date: Mon, 17 Nov 2025 16:24:01 +0100 Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] net: phylink: add missing supported link modes for the fixed-link To: "Russell King (Oracle)" , Wei Fang Cc: andrew@lunn.ch, hkallweit1@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, eric@nelint.com, imx@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251116023823.1445099-1-wei.fang@nxp.com> From: Maxime Chevallier Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 Hi, On 17/11/2025 16:17, Russell King (Oracle) wrote: > On Sun, Nov 16, 2025 at 10:38:23AM +0800, Wei Fang wrote: >> Pause, Asym_Pause and Autoneg bits are not set when pl->supported is >> initialized, so these link modes will not work for the fixed-link. This >> leads to a TCP performance degradation issue observed on the i.MX943 >> platform. >> >> The switch CPU port of i.MX943 is connected to an ENETC MAC, this link >> is a fixed link and the link speed is 2.5Gbps. And one of the switch >> user ports is the RGMII interface, and its link speed is 1Gbps. If the >> flow-control of the fixed link is not enabled, we can easily observe >> the iperf performance of TCP packets is very low. Because the inbound >> rate on the CPU port is greater than the outbound rate on the user port, >> the switch is prone to congestion, leading to the loss of some TCP >> packets and requiring multiple retransmissions. >> >> Solving this problem should be as simple as setting the Asym_Pause and >> Pause bits. The reason why the Autoneg bit needs to be set is because >> it was already set before the blame commit. Moreover, Russell provides >> a very good explanation of why it needs to be set in the thread [1]. >> >> [1] https://lore.kernel.org/all/aRjqLN8eQDIQfBjS@shell.armlinux.org.uk/ >> >> Fixes: de7d3f87be3c ("net: phylink: Use phy_caps_lookup for fixed-link configuration") >> Signed-off-by: Wei Fang >> Reviewed-by: Maxime Chevallier > > Even though discussion is still going on, we do need to fix this > regression. So: > > Reviewed-by: Russell King (Oracle) I already reviewed the patch, but I agree with Russell. Being the author of the blamed commit, I can say that this change in behavior was not intentional :( Maxime