From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Chulski Subject: RE: [PATCH net-next 5/5] net: mvpp2: jumbo frames support Date: Sun, 4 Mar 2018 09:42:39 +0000 Message-ID: <7d2e6deeb8a8435593b5c08615b192e1@IL-EXCH01.marvell.com> References: <20180302154044.25204-1-antoine.tenart@bootlin.com> <20180302154044.25204-6-antoine.tenart@bootlin.com> <20180302171713.54beaad0@windsurf.lan> <31a2c6c988bd4d5190e1fb3332f3bc35@IL-EXCH01.marvell.com> <20180304102828.1437fbc3@windsurf.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Cc: Antoine Tenart , "davem@davemloft.net" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "maxime.chevallier@bootlin.com" , "gregory.clement@bootlin.com" , "miquel.raynal@bootlin.com" , Nadav Haklai , Yan Markman , "mw@semihalf.com" To: Thomas Petazzoni Return-path: In-Reply-To: <20180304102828.1437fbc3@windsurf.home> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org > > To perform checksum in HW, HW obviously should work in store and > forward mode. Store all frame in TX FIFO and then check checksum. > > If mtu 1500B, everything fine and all port can do this. > > > > If mtu is 9KB and 9KB frame transmitted, Port 0 still can do HW checksum. > But ports 1 and 2 doesn't has enough FIFO for this. > > So we cannot offload this feature and SW should perform checksum. > > So perhaps the real check should not be "port 0", but whether the MTU is > higher or lower than the TX FIFO size assigned to the current port. > This would express in much better way the reason why HW checksum can be > used or not. I really don't want involve MTU size here, for each packet we should add to MTU overhead added by HW(offset, CRC, DSA tags and etc). I prefer just to check: port TX FIFO size is 10KB -> port can support HW checksum offload. Do you suggest to keep some shadow table with ports TX FIFO sizes for this? Thanks, Stefan.