Messages in this thread | | | From | Kurt Kanzenbach <> | Subject | Re: [PATCH net-next 08/13] net: dsa: hellcreek: deny tc-taprio changes to per-tc max SDU | Date | Wed, 21 Sep 2022 13:46:22 +0200 |
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On Wed Sep 21 2022, Vladimir Oltean wrote: > On Wed, Sep 21, 2022 at 01:23:24PM +0200, Kurt Kanzenbach wrote: >> On Thu Sep 15 2022, Vladimir Oltean wrote: >> > On Thu, Sep 15, 2022 at 08:15:54AM +0200, Kurt Kanzenbach wrote: >> >> > So the maxSDU hardware register tracks exactly the L2 payload size, like >> >> > the software variable does, or does it include the Ethernet header size >> >> > and/or FCS? >> >> >> >> This is something I'm not sure about. I'll ask the HW engineer when he's >> >> back from vacation. >> > >> > You can also probably figure this out by limiting the max-sdu to a value >> > like 200 and seeing what frame sizes pass through. >> >> So, configured to 128 and 132 bytes (including VLAN Ethernet header) is >> the maximum frame size which passes through. > > Frame size means MAC DA + MAC SA + VLAN header + Ethertype + L2 payload, > and without FCS, right?
Yes.
> > Because max_sdu 128 only counts the L2 payload, so the maximum frame > size that passes should be 142 octets, or 146 octets with VLAN.
Ok, i see. So, for 128 max-sdu we should end up with something like this in the prio config register:
schedule->max_sdu[tc] + VLAN_ETH_HLEN - 4
Thanks, Kurt [unhandled content-type:application/pgp-signature] | |