[Bug 215802] Re: rtl8187 link quality poor

Mon Jun 7 21:31:28 UTC 2010

Excerpt from a Linux-wireless discussion (this is Linux kernel
developer's list for wireless interfaces)

They asked me to do some tests: the major one was MMIO tracing the
driver:

> You need to enable MMIO tracing support in your kernel config, and
> recompile your kernel (assuming it is not enabled already - distros
> usually disable the entire tracing framework by default). Then:
> -Mount debugfs to /debug. (Usually it is mounted by default, but some
> distros like to mount it @ /sys/kernel/debug instead - remount it to
> /debug.)
> -"echo mmiotrace > /debug/tracing/current_tracer"
> -"cat /debug/tracing/trace_pipe >  trace.txt &" - at this point, tracing begins.
> -Load r8187b and connect.
> -"echo "Driver loaded!" > /debug/tracing/trace_marker"
> -"echo nop

Ok here are some news: 

1) The rtl8187b problem is a know bug in Ubuntu since forever - bug
#215802 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/215802

2) Tryied the Realtek driver found in: 
http://ubuntuforums.org/showthread.php?t=1446894 
(rtl8187B_linux_26.1056.1112.2009.release.tar.gz )

- as seno said here on the list in 14-05-2010 17:20:02

It installs a module called r8187b, witch I managed to use ONCE, after
it installed, then after it disconnected it would not connect again, and
after I rebooted there was no more wi-fi interface (!!!) ifconfig and
iwconfig confirm that my wi-fi card (wlan0) is nowhere to be found

5) Rate seems weird on this card. If I define the rate with 
"iwconfig wlan0 rate 11M" it gives the best download speed, even if I
rase this to 24M or 54M I get at least a 40% difference, same if I lower
the rate. 
Maybe what Hin-Tak Leung (2010-04-03) said about the Minstrel algorithm?
Could we try to install both Minstrel and older algorithms side by side
and make a comparison? from what I read here: 

http://wireless.kernel.org/en/developers/Documentation/mac80211/RateControl/minstrel
"Further, it means that the 1 Mbps rate (which typically has a high
probability of successful transmission) will not be used in preference
to the 11 Mbps rate." 

But my rate is always a defaulted 1Mb/s on bootup. I put it to 11M
manually and the connection improves dramatically 

4) Ran the mmiotrace on the rtl8187 driver, it all seems gibberish to
me ;) 

one while it was at 1m from the router giving me top speed (same as
Win7): trace1.txt:

VERSION 20070824
PCIDEV 0000 10390671 0 d0000000 0 0 0 0 0 0 8000000 0 0 0 0 0 0
agpgart-sis
PCIDEV 0008 10390003 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
PCIDEV 0010 10390968 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
PCIDEV 0015 10395513 10 1f0 3f6 170 376 1081 0 0 8 0 8 0 10 0 0 pata_sis
PCIDEV 0018 10397001 14 d8404000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ohci_hcd
PCIDEV 0019 10397001 15 d8405000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ohci_hcd
PCIDEV 001b 10397002 16 d8406000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ehci_hcd
PCIDEV 0020 10390191 13 d8407000 1001 0 0 0 0 0 80 80 0 0 0 0 0 sis190
PCIDEV 0028 10391183 11 10c9 10bd 10c1 10b9 10a1 0 0 8 4 8 4 10 0 0
sata_sis
PCIDEV 0030 1039000a 18 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0038 1039000a 19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0078 10397502 12 d8400000 0 0 0 0 0 0 4000 0 0 0 0 0 0 HDA Intel
PCIDEV 00f8 10390004 1a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0100 10396351 10 c0000008 d8000000 9001 0 0 0 2 10000000 20000 80
0 0 0 0 
PCIDEV 0300 197b2382 10 d8100000 0 0 0 0 0 d8500000 100 0 0 0 0 0 10000
sdhci-pci
PCIDEV 0302 197b2381 10 d8100400 0 0 0 0 0 0 100 0 0 0 0 0 0 
PCIDEV 0303 197b2383 10 d8100800 0 0 0 0 0 0 100 0 0 0 0 0 0 jmb38x_ms

** then when it was about 10m - failed to connect (Windows 7 connects
normally) trace2.txt 

VERSION 20070824
PCIDEV 0000 10390671 0 d0000000 0 0 0 0 0 0 8000000 0 0 0 0 0 0
agpgart-sis
PCIDEV 0008 10390003 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
PCIDEV 0010 10390968 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
PCIDEV 0015 10395513 10 1f0 3f6 170 376 1081 0 0 8 0 8 0 10 0 0 pata_sis
PCIDEV 0018 10397001 14 d8404000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ohci_hcd
PCIDEV 0019 10397001 15 d8405000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ohci_hcd
PCIDEV 001b 10397002 16 d8406000 0 0 0 0 0 0 1000 0 0 0 0 0 0 ehci_hcd
PCIDEV 0020 10390191 13 d8407000 1001 0 0 0 0 0 80 80 0 0 0 0 0 sis190
PCIDEV 0028 10391183 11 10c9 10bd 10c1 10b9 10a1 0 0 8 4 8 4 10 0 0
sata_sis
PCIDEV 0030 1039000a 18 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0038 1039000a 19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0078 10397502 12 d8400000 0 0 0 0 0 0 4000 0 0 0 0 0 0 HDA Intel
PCIDEV 00f8 10390004 1a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 pcieport
PCIDEV 0100 10396351 10 c0000008 d8000000 9001 0 0 0 2 10000000 20000 80
0 0 0 0 
PCIDEV 0300 197b2382 10 d8100000 0 0 0 0 0 d8500000 100 0 0 0 0 0 10000
sdhci-pci
PCIDEV 0302 197b2381 10 d8100400 0 0 0 0 0 0 100 0 0 0 0 0 0 
PCIDEV 0303 197b2383 10 d8100800 0 0 0 0 0 0 100 0 0 0 0 0 0 jmb38x_ms

*** All the steps asked by Gábor were done.

Thanks all you guys.

Rogerio

-- 
rtl8187 link quality poor
https://bugs.launchpad.net/bugs/215802
You received this bug notification because you are a member of Kernel
Bugs, which is subscribed to linux in ubuntu.