On 2012-04-15 7:21 PM, Gabor Juhos wrote: > Hi Felix, > > Thank you for the comments. > >> On 2012-04-14 10:01 PM, Gabor Juhos wrote: >>> The REDUCE_SCALED_POWER_BY_THREE_CHAIN symbol is >>> defined in different eeprom files, and the value >>> varies between the different files. >>> >>> In eeprom_def.c and in ar9003_eeprom.c the value >>> of the symbol is 9, however the comments in these >>> files indicates the value should be 10*log10(3)*2 >>> which is 9.54242509439325. Replace the the value >>> to 10 in these files. >>> >>> Also add comments to eeprom_9287.c. >>> >>> Signed-off-by: Gabor Juhos <juhosg@xxxxxxxxxxx> >> I think we should keep the value 9. >> If I understand the logic behind the power increase through chain >> combining properly, this value only describes the worst-case (wrt. >> regulatory compliance) upper limit of tx power, whereas in practice the >> measured combined power output will be much lower than that due to >> signal/phase differences. >> Regulatory compliance is already properly tested on all devices with the >> truncated value 9, so I don't think that we need to be even more >> conservative and round up here. > > Ok, I will rework the patch. > > Apart from the inconsistency between the REDUCE_SCALED_POWER_BY_THREE_CHAIN > values, there is another thing which confuses me. > > In the 'ath9k_hw_set_*_power_cal_table' functions the driver uses the > REDUCE_SCALED_POWER_BY_THREE_CHAIN constant to reduce the power values. > In the 'ath9k_hw_update_regulatory_maxpower' function it uses the > INCREASE_MAXPOW_BY_THREE_CHAIN constant to compensate the reduction. However the > two constants are different. I might be wrong, but in my opinion the driver > should use the same constant in both functions. I just checked with Atheros sources, and it seems I was wrong about sticking with the value 9. It appears that Atheros changed it to 10 at some point, and ath9k contains a mix of the old and the new version. Consistently using the value 10 for 3 chains for both increase and reduction seems to be the right thing to do. - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
