On 9/17/19 3:40 AM, Chris Chiu wrote: > 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 Realtek driver > at https://github.com/lwfinger/rtl8723bu, the same iperf test gets > ~12Mbps or better. The signal strength is reported similarly around > -40dBm. That's why we want to improve. > > After reading the source code of the rtl8xxxu driver and Realtek's, the > major difference is that Realtek'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. > > With this commit, the tx rate of each data and qos data packet will > be 39Mbps (MCS4) with the 0xF00000 as the tx rate mask. The 20th bit > to 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 always 0xFFFFFFF ranges from the basic CCK rate, OFDM rate, > and MCS rate. However, with Realtek's driver, the tx rate observed from > wireshark under the same condition is almost 65Mbps or 72Mbps, which > indicating that rtl8xxxu could still be further improved. > > Signed-off-by: Chris Chiu <chiu@xxxxxxxxxxxx> > Reviewed-by: Daniel Drake <drake@xxxxxxxxxxxx> I am still traveling after Plumbers and don't have my 8723bu dongles with me, but I'd say this looks good. Acked-by: Jes Sorensen <Jes.Sorensen@xxxxxxxxx> Jes
