rtl8xxxu: Wi-Fi Alliance Certification on Realtek RTL8188CUS
From: Reto Schneider <hidden>
Date: 2021-05-10 15:15:24
Hi Jes, Hi all, Chris (writing code, testing) and me (testing) are working [1] on re-newing the Wi-Fi Alliance certification of an IoT gateway (STA) which uses the Realtek RTL8188CUS chip, and is (now) running Linux 5.10+ with the rtl8xxxu driver, firmware version 88.2 [2]. The existing certification [3] has been done using the RealTek-provided 8192cu driver [4] and and Linux 3.19. While the rtl8xxxu in upstream is *very* stable, it lacks some features which are needed for the certification. I tried to summarize this in the wiki [1]. The following has been implemented by Chris (on top of mainline): - STBC Receive - TX power configuration (using the iw command, not regdb) Still missing: - WMM support - A-MSDU RX support - TX power by rate WIP (See also Chris' mail from earlier today): - A-MPDU - Rate adaption - TX descriptors The motivation for writing this mail is that we we are currently blocked by an issue which we can not resolve already for some months: The re-transmission percentage of the rtl8xxxu is too high (rtl8192cu is the same) - way higher than what 8192cu achieves. According to Wireshark, the retransmission rate is always between 15-65% for the rtl8xxxu, while the realtek-provided 8192cu stays below 5%, often averaging at less than 1% in my setup. Examples with an Linksys WRT3200ACM AP (RA/TA: 24:f5:a2:c0:4e:b1, DA/SA: 00:60:6e:00:07:7d, SSID customer-testwifi) and the DUT (00:1d:43:c0:19:8a) running iperf3 (TCP, TX): rtl8xxxu: - 65% retries, many addresses reported which do not actually exists - Code: [5] - Captures: [7] 891cu: - 0.9% retries, no ghost addresses captured - Code: [6] - Captures: [8] I'd be really grateful for any kind of ideas, pointers, help. Kind regards, Reto [1] Wiki entry (slightly outdated): https://wireless.wiki.kernel.org/en/users/wi-fi-alliance-certification [2] rtl8912cu firmware v88.2, part of linux-firmware 20201118: https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/rtlwifi/rtl8192cufw_TMSC.bin?id=2ea86675db1349235e9af0a9d0372b72da4db259 [3] Existing certification: https://api.cert.wi-fi.org/api/certificate/download/public?variantId=14856 [4] https://github.com/husqvarnagroup/smart-garden-gateway-seluxit-8192cu [5] Most recent rtl8xxxu development: https://github.com/husqvarnagroup/linux/commit/909f13c8fd45260a622d148882030624d492c54f [6] 8192cu for Linux 5.10+: https://github.com/husqvarnagroup/realtek-8192cu_rtl8188cus [7] pcap: https://files.reto-schneider.ch/diesunddas/rtl8xxxu/2021-05-10/rtl8xxxu-65%25-retries.pcapng.gz shell: https://files.reto-schneider.ch/diesunddas/rtl8xxxu/2021-05-10/rtl8xxxu-65%25-retries-shell.log [8] pcap: https://files.reto-schneider.ch/diesunddas/rtl8xxxu/2021-05-10/8192cu-0.9%25-retries.pcapng.gz shell: https://files.reto-schneider.ch/diesunddas/rtl8xxxu/2021-05-10/8192cu-0.9%25-retries-shell.log