From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55794C4332F for ; Mon, 19 Dec 2022 12:01:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231994AbiLSMBe (ORCPT ); Mon, 19 Dec 2022 07:01:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231686AbiLSMA7 (ORCPT ); Mon, 19 Dec 2022 07:00:59 -0500 Received: from phobos.denx.de (phobos.denx.de [85.214.62.61]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F924FCFE; Mon, 19 Dec 2022 04:00:14 -0800 (PST) Received: from wsk (85-222-111-42.dynamic.chello.pl [85.222.111.42]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: lukma@denx.de) by phobos.denx.de (Postfix) with ESMTPSA id 13364839D5; Mon, 19 Dec 2022 13:00:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=denx.de; s=phobos-20191101; t=1671451212; bh=7Tc08O5/QSZU9JKvbwkVI7bh4NdF+iLSTXKKDKKb9+I=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FIrpeZz0t4AmQgZz1wwK6gVNwP0i0bnsweCmFKA8xLVCdqRCkB4wNKYDigrokRJHv eqL8iXcu7SRq1bJGFy1Gyfzj1+p1Lc6qwC+ImrMOOX6HNgiYX3BBVOKXR+btocEDtQ +JgtvF/ioC01E+HujxsDwrHEYeCuAqu1oRIM4RdjRo/7lc4HNpaX1ZWJ5DZOaHnWOD yQOVNi6BcP0r/TLVw7kRzQ4huAInstETGDTkP8P3iCz4WTdfSlr0yVHd9x1tAS5ix/ v8W5pgMhtPiXcOPUhFyqYA+NkexojHdLxzbXDYJm1IGPt6pOBgHjm/XmEaFF+7zXoC 2HgBnd/JKEfFw== Date: Mon, 19 Dec 2022 13:00:05 +0100 From: Lukasz Majewski To: Alexander Duyck Cc: Andrew Lunn , Vladimir Oltean , Vivien Didelot , Florian Fainelli , "David S. Miller" , Jakub Kicinski , Russell King , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] dsa: marvell: Provide per device information about max frame size Message-ID: <20221219130005.6e995cb0@wsk> In-Reply-To: References: <20221215144536.3810578-1-lukma@denx.de> <4d16ffd327d193f8c1f7c40f968fda90a267348e.camel@gmail.com> <20221216140526.799bd82f@wsk> Organization: denx.de X-Mailer: Claws Mail 3.19.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/7XCBTm3tbk2vu6GHzeVhVz3"; protocol="application/pgp-signature"; micalg=pgp-sha512 X-Virus-Scanned: clamav-milter 0.103.6 at phobos.denx.de X-Virus-Status: Clean Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --Sig_/7XCBTm3tbk2vu6GHzeVhVz3 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Alexander, > On Fri, Dec 16, 2022 at 5:05 AM Lukasz Majewski wrote: > > > > Hi Alexander, > > =20 > > > On Thu, 2022-12-15 at 15:45 +0100, Lukasz Majewski wrote: =20 > > > > Different Marvell DSA switches support different size of max > > > > frame bytes to be sent. > > > > > > > > For example mv88e6185 supports max 1632 bytes, which is now > > > > in-driver standard value. On the other hand - mv88e6250 supports > > > > 2048 bytes. > > > > > > > > As this value is internal and may be different for each switch > > > > IC, new entry in struct mv88e6xxx_info has been added to store > > > > it. > > > > > > > > Signed-off-by: Lukasz Majewski > > > > --- > > > > Changes for v2: > > > > - Define max_frame_size with default value of 1632 bytes, > > > > - Set proper value for the mv88e6250 switch SoC (linkstreet) > > > > family --- > > > > drivers/net/dsa/mv88e6xxx/chip.c | 13 ++++++++++++- > > > > drivers/net/dsa/mv88e6xxx/chip.h | 1 + > > > > 2 files changed, 13 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c > > > > b/drivers/net/dsa/mv88e6xxx/chip.c index > > > > 2ca3cbba5764..7ae4c389ce50 100644 --- > > > > a/drivers/net/dsa/mv88e6xxx/chip.c +++ > > > > b/drivers/net/dsa/mv88e6xxx/chip.c @@ -3093,7 +3093,9 @@ static > > > > int mv88e6xxx_get_max_mtu(struct dsa_switch *ds, int port) if > > > > (chip->info->ops->port_set_jumbo_size) return 10240 - > > > > VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN; else if > > > > (chip->info->ops->set_max_frame_size) > > > > - return 1632 - VLAN_ETH_HLEN - EDSA_HLEN - > > > > ETH_FCS_LEN; > > > > + return (chip->info->max_frame_size - VLAN_ETH_HLEN > > > > + - EDSA_HLEN - ETH_FCS_LEN); > > > > + > > > > return 1522 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN; > > > > } > > > > > > > > =20 > > > > > > Is there any specific reason for triggering this based on the > > > existance of the function call? =20 > > > > This was the original code in this driver. > > > > This value (1632 or 2048 bytes) is SoC (family) specific. > > > > By checking which device defines set_max_frame_size callback, I > > could fill the chip->info->max_frame_size with 1632 value. > > =20 > > > Why not just replace: > > > else if (chip->info->ops->set_max_frame_size) > > > with: > > > else if (chip->info->max_frame_size) > > > =20 > > > > I think that the callback check is a bit "defensive" approach -> > > 1522B is the default value and 1632 (or 10240 - jumbo) can be set > > only when proper callback is defined. > > =20 > > > Otherwise my concern is one gets defined without the other > > > leading to a future issue as 0 - extra headers will likely wrap > > > and while the return value may be a signed int, it is usually > > > stored in an unsigned int so it would effectively uncap the MTU. =20 > > > > Please correct me if I misunderstood something: > > > > The problem is with new mv88eXXXX devices, which will not provide > > max_frame_size information to their chip->info struct? > > > > Or is there any other issue? =20 >=20 > That was mostly my concern. I was adding a bit of my own defensive > programming in the event that somebody forgot to fill out the > chip->info. If nothing else it might make sense to add a check to > verify that the max_frame_size is populated before blindly using it. > So perhaps you could do something similar to the max_t approach I had > called out earlier but instead of applying it on the last case you > could apply it for the "set_max_frame_size" case with 1632 being the > minimum and being overwritten by 2048 if it is set in max_frame_size. I think that I shall add: else if (chip->info->ops->set_max_frame_size) return max_t(int, chip->info->max_frame_size, 1632) - (headers) So then the "default" value of 1632 will be overwritten by 2048 bytes. Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de --Sig_/7XCBTm3tbk2vu6GHzeVhVz3 Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEgAyFJ+N6uu6+XupJAR8vZIA0zr0FAmOgUkUACgkQAR8vZIA0 zr0IIgf8DFwX5ALMURFb3pBxRfxtz7QWbOAhFlH5dZMui438mh4Yt8vRsW05YSm0 JT82EGxvq+o9XaCZh+7zIRtXa/gRJwOBnIYZ3Ouz/JDVAkLPd/qEbeilIlNVw9YU apvXST3vFR8O6GxwoT7zZhT/rK6lVhIzhmpEZXzuIOXXPKW26aQL+llHeTAN1/ha rJ9MS0bPgScyUQzZb/SbqhgCrDPPk8GfO7bhOQl8/8wzRiwmEqeTZFH72bXbIh60 mMFJFzXeigGRoAia3R/zioa4er7/6licKMhKiUyeOM4hMjxn5FKQteCnJVhsdCAZ yHcrIXTWMYjtg/WGeUYoWohcD9DliQ== =gxDE -----END PGP SIGNATURE----- --Sig_/7XCBTm3tbk2vu6GHzeVhVz3--