Messages in this thread | | | Date | Fri, 25 Nov 2022 23:40:33 +0200 | From | Vladimir Oltean <> | Subject | Re: [RFC Patch net-next v2 3/8] net: dsa: microchip: Initial hardware time stamping support |
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On Fri, Nov 25, 2022 at 07:06:07AM +0000, Arun.Ramadoss@microchip.com wrote: > KSZ switches need a additional 4 bytes in tail tag if the PTP is > enabled in hardware. If the PTP is enabled and if we didn't add 4 > additional bytes in the tail tag then packets are corrupted. > > Tristram explained this in the patch conversation > > https://lore.kernel.org/netdev/20201118203013.5077-1-ceggers@arri.de/T/#mb3eba4918bda351a405168e7a2140d29262f4c63 > > I did the follwing experiment today, > * Removed the ptp time stamp check in tag_ksz.c. In the ksz_xmit > function, 4 additional bytes are added only if KSZ_SKB_CB->ts_en bit is > set. > * Setup the board, ping two boards. Ping is successful. > * Run the ptpl in the background > * Now if I run the ping, ping is not successful. And also in the ptp4l > log message it shows as bad message received. > > We need a mechanism to inform tag_ksz.c to add 4 additional bytes in > tail_tag for all the packets if the ptp is enabled in the hardware.
Ok. The code + comments need to be sufficiently self-explanatory that this question does not get asked again. It will not be trivial to do a proper job documenting the hardware oddities as a justification for the software workarounds, but it should be possible.
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