Re: RTL8723bu: poor signal and connection troubles

[Carlo Caione]

On Sun, Jan 21, 2018 at 9:46 PM, Jes Sorensen  wrote:
> On 01/11/2018 05:30 AM, Barry Day wrote:

> One issue with rtl8723bu is that it needs to coexist with the bluetooth
> driver. When I wrote the rtl8723bu support that was no BT support for
> the chip in the kernel and it worked fine, at least for me. However if
> you load the BT driver for the dongle which someone pushed into the
> kernel since then, it is likely to hijack the antennas causing the weak
> signal you describe.

Yeah, that's why when testing the dongle I carefully disabled BT and
made sure no BT driver was probed at all. Still I can see the issue.
I honestly doubt that the problem is caused by BT coexistence. Any
other idea or suggestion to debug this problem?

Thanks,

-- 
Carlo Caione  |  +44.7384.69.16.04  |  Endless

Re: RTL8723bu: poor signal and connection troubles

[Jes Sorensen]

On 01/11/2018 05:30 AM, Barry Day wrote:
> On Wed, Jan 10, 2018 at 12:15:51PM +, 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.

One issue with rtl8723bu is that it needs to coexist with the bluetooth
driver. When I wrote the rtl8723bu support that was no BT support for
the chip in the kernel and it worked fine, at least for me. However if
you load the BT driver for the dongle which someone pushed into the
kernel since then, it is likely to hijack the antennas causing the weak
signal you describe.

Jes

Re: RTL8723bu: poor signal and connection troubles

[Carlo Caione]

On Wed, Jan 10, 2018 at 12:15 PM, 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.

Jes,
anything to comment about this issue? (ping)

-- 
Carlo Caione  |  +44.7384.69.16.04  |  Endless

Re: RTL8723bu: poor signal and connection troubles

[Barry Day]

On Wed, Jan 10, 2018 at 12:15:51PM +, 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

RTL8723bu: poor signal and connection troubles

[Carlo Caione]

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