From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH net-next 1/3] net: bgmac: Pad packets to a minimum size Date: Thu, 9 Nov 2017 15:03:16 -0800 Message-ID: <513068b8-132c-5fab-7639-a34f008e7a9c@gmail.com> References: <20171109222606.2987-1-f.fainelli@gmail.com> <20171109222606.2987-2-f.fainelli@gmail.com> <20171109223727.GC25275@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, vivien.didelot@savoirfairelinux.com To: Andrew Lunn Return-path: Received: from mail-qk0-f195.google.com ([209.85.220.195]:50263 "EHLO mail-qk0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754993AbdKIXDU (ORCPT ); Thu, 9 Nov 2017 18:03:20 -0500 Received: by mail-qk0-f195.google.com with SMTP id p7so9821422qkd.7 for ; Thu, 09 Nov 2017 15:03:19 -0800 (PST) In-Reply-To: <20171109223727.GC25275@lunn.ch> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 11/09/2017 02:37 PM, Andrew Lunn wrote: > On Thu, Nov 09, 2017 at 02:26:04PM -0800, Florian Fainelli wrote: >> In preparation for enabling Broadcom tags with b53, pad packets to a >> minimum size of 64 bytes (sans FCS) in order for the Broadcom switch to >> accept ingressing frames. Without this, we would typically be able to >> DHCP, but not resolve with ARP because packets are too small and get >> rejected by the switch. > > Hi Florian > > Is the MAC sending runt packets in its default configuration? Is this > a general issue, and not just an issue when there is a switch directly > attached? The MAC is sending 64 bytes (with FCS) padded packets by default, but this apparently gets mis-calculated when Broadcom tags are enabled, such that we need to pad before to avoid that. -- Florian