Dear gents, this is just a slightly off topic gratuitous side note.
In the context of fumbling in the "igb" driver in the other thread, I also took a look inside driver "igc" for comparison = to see what the i225 had to offer. Unsurprisingly, the register map related to time sync features seems quite similar to that of the i210. The source code of igc_ptp.c is pretty clean. The datasheet for the i225 is not public yet and I don't have it, so I cannot comment further. Interestingly to me, the TIMADJ register is now mentioned, but only to set some novel flag/bit in that register during port init/reset... For stepwise time adjustment, the SYSTIM registers get written directly :-) I'm aware of the initial bug in framing (the Inter-Packet Gap), when the i225 silicon was first launched... and I've seen recent complaints about the B3 revision, that the chip sometimes dies (and a NIC firmware update is supposed to fix this). Those baby maladies aside, it looks like a pretty sporty piece of silicon. While fumbling for current information, I've found the following memo: https://cdrdv2-public.intel.com/757442/757442_I225-226%20Time-Sensitiv e-Networking-Features-Brief.pdf Whoa. The thing supports 802.3br + 802.1Qbu. The dirtier secrets of the TSN. https://www.ieee802.org/3/br/Baseline/8023-IET-TF-1405_Winkel-iet-Base line-r3.pdf Not that I have any practical use for these, but it sure sounds arcane. This is a queueing/framing technology that allows high priority packets to preempt a long lazy packet in the middle of transmission, insert the high-priority packet, and after that gets transmitted, resume transmission of the long lazy packet - without having to drop the first part before preemption, without increasing the RX FCS err counter. I.e. graceful fragmentation and reassembly within/below L2 in Ethernet. Yes it does introduce an extra preamble or two, and the IPG also has to be observed... Pretty crazy stuff, by my standards :-) I've seen a switch or three, that claim to support the TSN, but none of them actually mentioned 802.3br among the plethora of TSN-related 802.x buzzwords. So much for my todays random rant, thanks for your attention :-) Frank _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
