Hm, do we have a sane way to get an unmolested RX timestamp? like, is there any twiddle we can do to use the second TSF on Kiwi and later and leave it free-running, so in STA mode we can get the RX timestamps from said free-running clock, rather than the hostap BSS adjusted TSF?
-a On 14 February 2014 02:50, Felix Fietkau <n...@openwrt.org> wrote: > On 2014-02-14 02:45, Dimosthenis Pediaditakis wrote: >> Hi all, >> I am using a capacity and available bandwidth measurement software that >> compute estimates based on the gaps among packet trains/pairs. >> >> For that reason I need to disable RX/TX interrupt mitigation for the >> devices that I take the measurement form, because it introduces skew, >> and renders unmeasurable the fast links (> 54Kbps). >> The less latencies the drivers+kernel introduces, the better. >> >> I have so far managed to disable all together the RX mitigation for >> mini-PCIe devices by hard-coding the following line in >> "linux/drivers/net/wireless/ath/ath9k/ hw.c" >> ah->config.rx_intr_mitigation = false; > It seems to me that a better way to do this would be to drop your > fragile software based time measurement of rx interrupts, and instead > use the hardware timestamp (measured in microseconds). > >> While the above trick improves my results, it doesn't change the >> behaviour of the Atheros-based USB WiFi dongles. >> AFAIK my TP-Link TL-WN722N USB dongle uses the ath9k_htc driver, but I >> haven't found anything relevant in the respective sources ( htc_*.{c, h} ) > There is no interrupt mitigation here. > >> Apart from that, I suspect that the USB-net driver itself might also >> introduce some fixed delays which affect the minimum time-spacing >> measurement that my software can perceive at the receiver side. > USB in general adds too much latency for what you want to do. > Use hardware timestamps here as well. > > - Felix > _______________________________________________ > ath9k-devel mailing list > ath9k-devel@lists.ath9k.org > https://lists.ath9k.org/mailman/listinfo/ath9k-devel _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel