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 27EF7C4332F for ; Fri, 16 Dec 2022 13:06:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230422AbiLPNGF (ORCPT ); Fri, 16 Dec 2022 08:06:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230437AbiLPNFr (ORCPT ); Fri, 16 Dec 2022 08:05:47 -0500 Received: from phobos.denx.de (phobos.denx.de [IPv6:2a01:238:438b:c500:173d:9f52:ddab:ee01]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DACF725EE; Fri, 16 Dec 2022 05:05:38 -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 A4C9384881; Fri, 16 Dec 2022 14:05:36 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=denx.de; s=phobos-20191101; t=1671195937; bh=v2hyP2ZH/dKnNRKXD+eheCejY2sZlWVOdtlMHVrs2lc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=zpUCmv+f/PKfpiFBdXAbepeTZPQkKaPxD9EZ0X+idM5hgFRm7rxDKL34Pi5ltGvQA cvBcm0JaqHVGB2/JhQHNXWTkfCztmUXxM/7wh718ahkBri1wjPAwendW+GdXs4qNfc LNfl/7E8zaOtBWy1cng1X/g4oTYySgTLUwJepragKQxvP+AtBEo8e32Od++lNbULkU lF0z1QFdHGSqHFlHzQjng1siEXd7EQ6dvkqGwaorFyP6S01BUGGU5KmfkMRl2pJV7F s7iI2rPBO01oKfdFi1QQdisv5VQ7m1k2W9+DfF0X7wR3YZyQUKdPc2bF0KiMWxH+xV GIPcYDIx4A+SA== Date: Fri, 16 Dec 2022 14:05:26 +0100 From: Lukasz Majewski To: Alexander H 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: <20221216140526.799bd82f@wsk> In-Reply-To: <4d16ffd327d193f8c1f7c40f968fda90a267348e.camel@gmail.com> References: <20221215144536.3810578-1-lukma@denx.de> <4d16ffd327d193f8c1f7c40f968fda90a267348e.camel@gmail.com> 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_/nCzLGEgU8x4RN6D+MU=naZZ"; 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_/nCzLGEgU8x4RN6D+MU=naZZ Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Alexander, > On Thu, 2022-12-15 at 15:45 +0100, Lukasz Majewski wrote: > > Different Marvell DSA switches support different size of max frame > > bytes to be sent. > >=20 > > For example mv88e6185 supports max 1632 bytes, which is now > > in-driver standard value. On the other hand - mv88e6250 supports > > 2048 bytes. > >=20 > > 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. > >=20 > > 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(-) > >=20 > > 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 > > =20 >=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. > 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. > 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. 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 > Actually you could take this one step further since all values should > be 1522 or greater you could just drop the else/if and replace the > last line with "max_t(int, chip->info->max_frame_size, 1522) - > (headers)". This would be possible, yes. However, then we will not check if the proper callback (e.g. chip->info->ops->set_max_frame_size) is available for specific SoC. If this is OK for maintainers for this driver, then I don't mind. 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_/nCzLGEgU8x4RN6D+MU=naZZ Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEgAyFJ+N6uu6+XupJAR8vZIA0zr0FAmOcbRcACgkQAR8vZIA0 zr38sggAoqoz/XJ1GyUjOFPHF9eVrTISta2YQ/2HM9q8L5hN3Hkh32xkYCI/62HO OsoE2qrYUMLsaa0ei0qu6Qv5NnUBEpazOt6XcMFoyawmUjAZdvboxGO7eFZoFd9J hk5kcJBTdXEHDEDsYY7ynpJIbHDGKhYj2uvGr9fRR7Lx4xfCOIZ7G5hc49HGS7y5 lBJuQxhmLCVwUiQmCANSWaeuQfHnldehxrS7gdrEkbMIlT+jVnaQ9G+z2mm0UjA0 K+euWcWwgDosk/j8KP/XU1Gw6i1hiMG/CyiK3z7l7iFC/F/7HjPR0iclzvCpU+PI vDR1hTdvFTyvphpaQyaZyk7d8C4a6Q== =tt9B -----END PGP SIGNATURE----- --Sig_/nCzLGEgU8x4RN6D+MU=naZZ--