On Wed, Jan 10, 2018 at 12:15:51PM +0000, Carlo Caione wrote:

Hi,
this is a follow up email to [0] since the problem was never fully
investigated / solved and I keep seeing the same problem also on my
hardware.

Also in my case the hardware is a rtl8723bt transceiver
(0x0bda:0xb720), this time shipped on the internal USB bus in a cheap
laptop branded Zyrex Sky 232.

As already reported by Mylene the problem is that using this
transceiver and the latest Linus master you can barely see any WiFi
network around and also when a WiFi network is actually seen, the
connection is impossible since the signal strength is too low to have
a reliable connection. Of course during my tests BT is off and no BT
driver is probed at all.

Using the downstream driver at [1] everything works correctly.

I tried to debug a bit the issue, in particular comparing functions
and registers related to the antenna setup (.power_on, .enable_rf,
.phy_init_antenna_selection, .phy_iq_calibrate hooks) but everything
seems pretty much the same on the two drivers (even though slightly
differences do exist).

Any idea / suggestion on how to debug this problem? I guess it's worth
to start looking at this since several platforms are being affected
now.

Cheers,

[0] https://www.spinics.net/lists/netdev/msg468028.html
[1] https://github.com/lwfinger/rtl8723bu

-- 
Carlo Caione  |  +44.7384.69.16.04  |  Endless

I've found the same. The signal strength using the original driver
from Realtek is significantly higher than when using rtl8xxxu.
I also was not able to find anything wrong in the rtl8xxxu source code
that would be causing the difference, which leads to the thought it is
missing something that exists in the original driver.


Barry Day