From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relmlie5.idc.renesas.com (relmlor1.renesas.com [210.160.252.171]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7CB873B1A1; Mon, 17 Jun 2024 14:03:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.160.252.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718633013; cv=none; b=OYDsDwXsY26LOOgW+5eCmuiXVSYpViFzAvY/kRc5IIsVvA/rj4FAeBuyU9Rt+7Fjru0mOVYHffD9RcD1ZRCurEWbplqm2VlPDXzQrfNx3j5atO4Ld3gkScSiJ1sGqoRrSqpm3hK+iVLglAMqBte2uE09U/tCK0lkKqMzrP7ziYU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718633013; c=relaxed/simple; bh=4Wk2uUHFGwBTd8590+ukd6SHK0BLyByUgTCriUPM4yI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rw1Xz+1cwjBPnBmC0bfJMtk7FazAusC5FvXD/a7dC4B7Y0omBEodCaUZa5r80UVXWVxxrgBq/0RoVWUslBbIXwfhdTWhgHtPYTxcyGn9dr/7XUdafqW8CUDJmviYAQXWU3o6YDUO1dcz79Nb0FA39RQExH2TAMcBLXobO+qyh7Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=bp.renesas.com; spf=pass smtp.mailfrom=bp.renesas.com; arc=none smtp.client-ip=210.160.252.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=bp.renesas.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bp.renesas.com X-IronPort-AV: E=Sophos;i="6.08,244,1712588400"; d="asc'?scan'208";a="208261329" Received: from unknown (HELO relmlir6.idc.renesas.com) ([10.200.68.152]) by relmlie5.idc.renesas.com with ESMTP; 17 Jun 2024 23:03:27 +0900 Received: from [10.226.92.92] (unknown [10.226.92.92]) by relmlir6.idc.renesas.com (Postfix) with ESMTP id 134424394971; Mon, 17 Jun 2024 23:03:22 +0900 (JST) Message-ID: <933ffa58-8092-4768-993d-cd62897d203d@bp.renesas.com> Date: Mon, 17 Jun 2024 15:03:21 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [net-next PATCH 2/2] net: ravb: Fix R-Car RX frame size limit Content-Language: en-GB To: Andrew Lunn Cc: Sergey Shtylyov , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , =?UTF-8?Q?Niklas_S=C3=B6derlund?= , Biju Das , Claudiu Beznea , Lad Prabhakar , Mitsuhiro Kimura , netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240615103038.973-1-paul.barker.ct@bp.renesas.com> <20240615103038.973-3-paul.barker.ct@bp.renesas.com> From: Paul Barker Organization: Renesas Electronics Corporation In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------3oRCa9JXa8rEzNUJpWGX5HXa" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------3oRCa9JXa8rEzNUJpWGX5HXa Content-Type: multipart/mixed; boundary="------------sg0aRvFe07KycBt0Lop00RNu"; protected-headers="v1" From: Paul Barker To: Andrew Lunn Cc: Sergey Shtylyov , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , =?UTF-8?Q?Niklas_S=C3=B6derlund?= , Biju Das , Claudiu Beznea , Lad Prabhakar , Mitsuhiro Kimura , netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <933ffa58-8092-4768-993d-cd62897d203d@bp.renesas.com> Subject: Re: [net-next PATCH 2/2] net: ravb: Fix R-Car RX frame size limit References: <20240615103038.973-1-paul.barker.ct@bp.renesas.com> <20240615103038.973-3-paul.barker.ct@bp.renesas.com> In-Reply-To: --------------sg0aRvFe07KycBt0Lop00RNu Content-Type: multipart/mixed; boundary="------------mvw0FoEI0clK5poGQBBl8Kra" --------------mvw0FoEI0clK5poGQBBl8Kra Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 16/06/2024 02:23, Andrew Lunn wrote: > On Sat, Jun 15, 2024 at 11:30:38AM +0100, Paul Barker wrote: >> The RX frame size limit should not be based on the current MTU setting= =2E >> Instead it should be based on the hardware capabilities. >=20 > This is a bit odd. MTU is Maximum Transmission Unit, so clearly is > about Tx. MRU does not really exist. Does TCP allow for asymmetric > MTU/MRU? Does MTU discovery work correctly for this? >=20 > In general, it seems like drivers implement min(MTU, MRU) and nothing > more. Do you have a real use case for this asymmetry? >=20 > Andrew Hi Andrew, This change is based on my understanding of MTU/MRU, on the specs of the RZ SoCs I'm working with (primarily RZ/G2L family, RZ/G3S and RZ/G2H) and on some testing. My goal here is just to make the capabilities of the hardware available to users. For the RZ/G2L family and RZ/G3S, we can only support an MTU of up to 1500 bytes, but we can receive frames of up to (IIRC) 8192 bytes. I have tested sending jumbo frames to an RZ/G2L device using both iperf3 and ping and I see no errors. * For iperf3 RX testing, the RZ/G2L is only responding with acks. These are small regardless of the size of the received packets, so the mis-match in MTU between the two hosts causes no issue. * For ping testing, the RZ/G2L will give a fragmented response to the ping packet which the other host can reassemble. For the RZ/G2H, we support sending frames of up to 2047 bytes but we can receive frames of up to 4092 bytes. The driver will need a few more changes to handle reception of packets >2kB in size, but this is something we can do in the near future. Is there any reason why we shouldn't support this? I am by no means an expert in the Linux networking internals so there may be things I'm missing. 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