From: Andrew Lunn <andrew@lunn.ch>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>,
woojung.huh@microchip.com, UNGLinuxDriver@microchip.com,
vivien.didelot@gmail.com, f.fainelli@gmail.com,
davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] net: dsa: tag_ksz: dont let the hardware process the layer 4 checksum
Date: Thu, 15 Jul 2021 15:08:53 +0200 [thread overview]
Message-ID: <YPAzZXaC/En3s4ly@lunn.ch> (raw)
In-Reply-To: <20210715065455.7nu7zgle2haa6wku@skbuf>
> - If we inherit NETIF_F_HW_CSUM from the master for tail taggers, it is
> actively detrimential to keep this feature enabled, as proven my Lino.
> As for header taggers, I fail to see how this would be helpful, since
> the DSA master would always fail to see the real IP header (it has
> been pushed to the right by the DSA tag), and therefore, the DSA
> master offload would be effectively bypassed.
The Marvell MACs know about DSA and should be able to perform hardware
checksumming. It is a long time since i looked at how this works, but
i think there is a field in the descriptor which gets set with the
offset to the IP header, so it work for DSA as well as EDSA.
I _think_ Broadcom MACs also know about Broadcom tags and can do the
right thing.
So we need to be a bit careful here to prevent performance regressions
for same vendor MAC+Switch combinations.
Andrew
next prev parent reply other threads:[~2021-07-15 13:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 19:17 [PATCH 0/2] Fixes for KSZ DSA switch Lino Sanfilippo
2021-07-14 19:17 ` [PATCH 1/2] net: dsa: tag_ksz: linearize SKB before adding DSA tag Lino Sanfilippo
2021-07-14 19:17 ` [PATCH 2/2] net: dsa: tag_ksz: dont let the hardware process the layer 4 checksum Lino Sanfilippo
2021-07-14 19:48 ` Vladimir Oltean
2021-07-14 20:15 ` Andrew Lunn
2021-07-15 6:54 ` Vladimir Oltean
2021-07-15 11:16 ` Aw: " Lino Sanfilippo
2021-07-15 11:49 ` Vladimir Oltean
2021-07-15 13:04 ` Aw: " Lino Sanfilippo
2021-07-15 13:12 ` Vladimir Oltean
2021-07-15 13:34 ` Aw: " Lino Sanfilippo
2021-07-15 13:08 ` Andrew Lunn [this message]
2021-07-15 14:36 ` Vladimir Oltean
2021-07-15 15:50 ` Andrew Lunn
2021-07-19 8:20 ` Aw: " Lino Sanfilippo
2021-07-19 8:24 ` Vladimir Oltean
2021-07-15 16:24 ` Florian Fainelli
2021-07-15 23:23 ` [PATCH 0/2] Fixes for KSZ DSA switch Florian Fainelli
2021-07-16 8:49 ` Aw: " Lino Sanfilippo
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