Messages in this thread | | | Date | Thu, 15 Jul 2021 15:08:53 +0200 | From | Andrew Lunn <> | Subject | Re: [PATCH 2/2] net: dsa: tag_ksz: dont let the hardware process the layer 4 checksum |
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> - 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
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