We have 3 laptops which connect the wifi by the same RTL8723BU. The PCI VID/PID of the wifi chip is 10EC:B720 which is supported. They have the same problem with the in-kernel rtl8xxxu driver, the iperf (as a client to an ethernet-connected server) gets ~1Mbps. Nevertheless, the signal strength is reported as around -40dBm, which is quite good. From the wireshark capture, the tx rate for each data and qos data packet is only 1Mbps. Compare to the driver from https://github.com/lwfinger/rtl8723bu, the same iperf test gets ~12 Mbps or more. The signal strength is reported similarly around -40dBm. That's why we want to find out the cause and improve. After reading the source code of the rtl8xxxu driver and Larry's, the major difference is that Larry's driver has a watchdog which will keep monitoring the signal quality and updating the rate mask just like the rtl8xxxu_gen2_update_rate_mask() does if signal quality changes. And this kind of watchdog also exists in rtlwifi driver of some specific chips, ex rtl8192ee, rtl8188ee, rtl8723ae, rtl8821ae...etc. They have the same member function named dm_watchdog and will invoke the corresponding dm_refresh_rate_adaptive_mask to adjust the tx rate mask. Thus I created 2 commits and try to do the same thing on rtl8xxxu. https://github.com/endlessm/linux/commit/503d0b6eb61f25984042b1f00e6293776ae722c7 https://github.com/endlessm/linux/commit/5b06665766d6c3e25cbf649022989a8f3abc83d6 The 1st commit brings a data structure for rate adaptive which will be useful for determining higher or lower the tx rate. The second commit adds a watchdog to monitor and update the tx rate mask and tell the firmware. After applying these commits, the tx rate of each data and qos data packet will be 39Mbps (MCS4) with the 0xf00000 as its tx rate mask. The 20th bit ~ 23th bit means MCS4 to MCS7. It means that the firmware still picks the lowest rate from the rate mask and explains why the tx rate of data and qos data is always lowest 1Mbps because the default rate mask passed is almost 0xFFFFFFF ranges from the basic CCK rate, OFDM rate, and MCS rate. However, with Larry's driver, the tx rate observed from wireshark under the same condition is almost 65Mbps or 72Mbps. I believe the firmware of RTL8723BU may need fix. And I think we can still bring in the dm_watchdog as rtlwifi to improve from the driver side. Please leave precious comments for my commits and suggest what I can do better to get them upstream. Or suggest if there's any better idea to fix this. Thanks. Chris
