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 0FEC71B8EAF; Thu, 15 Aug 2024 09:10:34 +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=1723713038; cv=none; b=F0GWAFbiyPFZ8bNSXCF06O5MMoaDo7A26eorGmoREvVsNK65nhvicWJCe95xe/rtAqqoBGUSHECcMdhd9sVUpztirxKzzH8fgwzm7YPcIWHnfnDGCtH0GpuuJ4rtgj1szRCDrrKBPPYSrAAFw+WR3O19ysq30wIsrcCZpMP+KIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723713038; c=relaxed/simple; bh=gXbtDV3Den7rYv5gxqLb1TBgiTVBk3gTcwJQqn4DZto=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hmN7rNlG/I1hR6U+F419+MBmK3i+i4O90QK3/vCdBXCMpB24kybJCFvpLz+sbJNGHglpCjexS/TTnMyHPc79udGQJEnPMR/XzlxZ/noCLt+ZTC419/9wnrQU8X5y979Fh1Q95+8/FEVmS76wu74Ef7V2D5mZgF+Ek4JRnx6CBl4= 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="6.10,148,1719846000"; d="asc'?scan'208";a="215659341" Received: from unknown (HELO relmlir6.idc.renesas.com) ([10.200.68.152]) by relmlie5.idc.renesas.com with ESMTP; 15 Aug 2024 18:10:27 +0900 Received: from [10.226.92.106] (unknown [10.226.92.106]) by relmlir6.idc.renesas.com (Postfix) with ESMTP id 6B69941B0FBE; Thu, 15 Aug 2024 18:10:23 +0900 (JST) Message-ID: <4e1034fb-daf6-4bdb-80d2-62536394fc2d@bp.renesas.com> Date: Thu, 15 Aug 2024 10:10:21 +0100 Precedence: bulk X-Mailing-List: netdev@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 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> <933ffa58-8092-4768-993d-cd62897d203d@bp.renesas.com> <524873e1-d770-4f29-a374-dab99fe87c14@bp.renesas.com> Content-Language: en-GB From: Paul Barker Organization: Renesas Electronics Corporation In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------erULbL10teRUTagGlpnZc7J2" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------erULbL10teRUTagGlpnZc7J2 Content-Type: multipart/mixed; boundary="------------VVx40Kl2aWXzy9BT3U745Et1"; 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: <4e1034fb-daf6-4bdb-80d2-62536394fc2d@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> <933ffa58-8092-4768-993d-cd62897d203d@bp.renesas.com> <524873e1-d770-4f29-a374-dab99fe87c14@bp.renesas.com> In-Reply-To: --------------VVx40Kl2aWXzy9BT3U745Et1 Content-Type: multipart/mixed; boundary="------------0pJW0lJQaD5HaO0BUI0PAW4f" --------------0pJW0lJQaD5HaO0BUI0PAW4f Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 13/08/2024 15:06, Andrew Lunn wrote: >> Apologies, my response here is abysmally late due to illness, other >> priorities and then the loss of my main dev box. >=20 > Not a problem, life happens. >=20 >> As you've said, a number of devices do not limit received packet size = to >> the MTU. There are many applications, other than a gateway, where usin= g >> jumbo packets in even just one direction would be beneficial. For >> example if an application needs to receive large amounts of data but >> only needs to send back control and acknowledgement messages. I think = we >> should support this where possible. This is the thought behind the fir= st >> patch in this series as the GbEth IP present in the RZ/G2L and other >> Renesas SoCs has a very asymmetric capability (it can receive 8000 byt= e >> frames but only transmit 1522 byte frames). >> >> If we explicitly do not wish to support this, that restriction should = be >> documented and then (maybe over time) handled uniformly for all networ= k >> drivers. >> >> I'm planning to submit v2 of this series shortly. >=20 > Does the hardware support scatter/gather? How does supporting jumbo > receive affect memory usage? Can you give the hardware a number of 2K > buffers, and it will use one for a typical packet, and 4 for a jumbo > frame? This is exactly what happens. After recent changes [1], we use 2kB RX buffers and an 8kB maximum RX frame size for the GbEth IP. The hardware will split the received frame over one or more buffers as needed. As we would allocate a ring of 2kB buffers in any case, supporting jumbo packets doesn't cause any increase in memory usage or in CPU time spent in memory management. 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