Hello, I have been chasing issues with hardware timestamp accuracy/asymmetry on the i211 and i354. I’ve come across references to a similar issue with the i210, and am hoping that someone can help shed light on this.
Based on some figures that were previously present in the i210 datasheet (table 7-62), the kernel version of the igb driver has added latency compensation for hardware timestamps on the i210 (only). The comment for the commit was: Table 7-62 on page 338 of the i210 datasheet lists TX and RX latencies for the various speeds the chip supports. To give better ptp timestamp accuracy, adjust the timestamps by the amounts Intel gives based on current link speed. The values in nanoseconds used were: TX_LATENCY_10 9542 TX_LATENCY_100 1024 TX_LATENCY_1000 178 RX_LATENCY_10 20662 RX_LATENCY_100 2213 RX_LATENCY_1000 448 However in the current i210 data sheet, table 7-62 only provides information for 100Mb. The information for 10Mb and 1Gb has apparently been removed. The current data sheet for the i211 contains the same content regarding timestamps (table 7-59), with the same values for Tx/Rx latency, but again only provides information for 100Mb. No information for 10Mb and 1Gb. The current data sheet for the i350 has no information on timestamp latency compensation at all. But in testing with the i354, Tx/Rx timestamping latency appears to be even more asymmetric than the i211. Does anyone know why the latency compensation values were removed from the i210 data sheet? Or any pointers to additional documentation of latency compensation for timestamps with chips supported by the igb driver? I would greatly appreciate anything you might have to offer. Many thanks, Denny ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
