From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Ungerer Subject: Re: [PATCH 0/3]: net: dsa: mt7530: support MT7530 in the MT7621 SoC Date: Mon, 3 Dec 2018 16:47:01 +1000 Message-ID: <06437893-2d15-a08e-8907-d246fb3e4a5b@kernel.org> References: <20181130075737.8041-1-gerg@kernel.org> <20181130133313.GB11747@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: sean.wang@mediatek.com, vivien.didelot@savoirfairelinux.com, f.fainelli@gmail.com, netdev@vger.kernel.org, blogic@openwrt.org, neil@brown.name To: Andrew Lunn Return-path: Received: from icp-osb-irony-out6.external.iinet.net.au ([203.59.1.106]:64450 "EHLO icp-osb-irony-out6.external.iinet.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725818AbeLCGrd (ORCPT ); Mon, 3 Dec 2018 01:47:33 -0500 In-Reply-To: <20181130133313.GB11747@lunn.ch> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: Hi Andrew, On 30/11/18 11:33 pm, Andrew Lunn wrote: >> 2. Maximal sized RX packets get silently dropped. So receive side packets >> that are large (perfect case is the all-but-last packets in a fragemented >> larger packet) appear to be dropped at the mt7621 ethernet MAC level. >> The 7530 MIB switch register counters show receive packets at the physical >> switch port side and at the CPU switch port - but I get no packets >> received or errors in the 7621 ethernet MAC. If I set the mtu of the >> server at the other end a little smaller (a few bytes is enough) then >> I get all the packets through. It seems like the DSA/VLAN tag bytes >> are causing a too large packet to get silently dropped somewhere. > > Hi Gerg > > Try increasing the MTU on the master device. Some hardware will reject > receiving packets bigger than the MTU. But if you increase the MTU by > the DSA header size, it will then receive the frame. I tried increasing it on the master, and it fails to set: # ifconfig eth0 mut 1500 # ifconfig eth0 mtu 1504 eth0: mtu greater than device maximum SIOCSIFMTU: Invalid argument Looking within that staging driver it seems to generously set the size of the RX descriptor buffers, so there is enough room in them. And glancing around the driver I don't see it using the MTU to restrict the receive packaet size (though I may be missing it). > I have a patchset i will be posting soon to do this automatically. That would be good. Regards Greg