On Mon, Aug 30, 2010 at 09:48:57AM -0500, Larry Finger wrote: > On 08/30/2010 09:12 AM, John W. Linville wrote: > > On Sat, Aug 28, 2010 at 04:32:48PM -0500, Larry Finger wrote: > >> On 08/28/2010 12:54 AM, Thadeu Lima de Souza Cascardo wrote: > >>> The code for rtl8187 does not do per packet TX AGC. Resetting the per > >>> packet TX AGC for rtl8187b appears to increase its overall TX power. > >>> This allows the device to associate and a connection be established > >>> using APs a little further away. > >>> > >>> Tested-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxxx> > >>> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxxx> > >>> Cc: linux-wireless@xxxxxxxxxxxxxxx > >>> Cc: Larry Finger <Larry.Finger@xxxxxxxxxxxx> > >>> Cc: Rogerio Luz Coelho <rogluz.news@xxxxxxxxx> > >>> Cc: Herton Ronaldo Krzesinski <herton@xxxxxxxxxxxxxxx> > >>> Cc: Hin-Tak Leung <hintak.leung@xxxxxxxxx> > >>> --- > >> > >> I'm a little confused here. The subject says not to set the per packet TX AGC, > >> while the submission text says that setting it helps. I don't have access to any > >> documents that describe this register, but I expect that clearing > >> RTL818X_TX_AGC_CTL_PERPACKET_GAIN_SHIFT would disable that feature. As a result > >> the code change seems to match the subject. > >> > >> I have not yet tested this code, but I do note that all the Realtek drivers for > >> the RTL8187B set this bit. > >> > >> Until testing, I withhold judgment on the actual code change, but NACK for the > >> inconsistency. > > > > Perhaps the word "clearing" rather than "resetting" would be less confusing? > Thanks, John, for the clarification. Clearing is much better, really. > I see the source of my confusion. I am in the habit of using lower case to > indicate the driver and upper case for the device. I would rewrite the commit > code to say "The code for the RTL8187L does not do per packet TX AGC. Clearing > the per packet TX AGC for RTL8187B ..." > I will use your rewriting. Thanks. > I have now tested the patch. For my RTL8187B device, I get the following: > > Distance from AP Indicated rate Signal Measured TX rate > 2m 18 Mb/s -17 dBm 10 Mb/s > 10m(original) 11 Mb/s -48 dBm 2.6 Mb/s > 10m(with patch) 11 Mb/s -43 dBm 4.1 Mb/s > > The measured TX rates were obtained using tcpperf. At a distance of 2 m, the > results were the same with and without the patch. At 10 m, the patch went > through 2 exterior walls with drywall, insulation, and stucco. I'm not sure that > the increase from 2.6 to 4.1 Mb/s is reproducible. About all I can say is that > the change did not hurt the performance of the device, which is already pretty bad. > > If the OP can post numbers documenting the improvement, I have no objection to > this patch, even though every Realtek driver that I have seen turns "per packet > TX AGC" on for the RTL8187B and turns it off for the RTL8187L. > Hum. Did you take a look at the version I've pointed out in the last message, rtl8187B_linux_26.1056.1112.2009.release? It does not clear PERPACKET_GAIN in the same function that it does for non-RTL8187B devices. But it does in what should be the code for RTL8225Z2, in the function r8180_rtl8225z2.c:InitializeExtraRegsOn8185. I did not measure the distances exactly here, while doing my tests. But I could move the AP further away by about 5 or 6 meters. The AP indicated a -84dB signal while receiving injected packages. It was a rt73usb device. File transmission through scp was not working that further away, but I could still get an improvement of about 3 to 4 meters of distance. I am still going to do some more testing today in a customer's facility. And I would like very much that Rogério, who has reported some problems too, did some testing. > Larry Best regards, Cascardo.
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