Jonas Jelonek <jelonek.jonas@xxxxxxxxx> writes: >> On 30. Mar 2023, at 11:31, Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: >> >> Jonas Jelonek <jelonek.jonas@xxxxxxxxx> writes: >> >>> Fix incorrect usage of plain rate_idx as index into the max (power) per >>> rate lookup table. >>> >>> For transmit power control (TPC), the ath9k driver maintains internal >>> tables (in struct ath_hw) to store the max allowed power level per rate. >>> They are used to limit a given TX-power according to regulatory and user >>> limits in the TX-path per packet. The tables are filled in a predefined >>> order, starting with values for CCK + OFDM rates and followed by the >>> values for MCS rates. Thus, the maximum power levels for MCS do not >>> start at index 0 in the table but are shifted by a fixed value. >>> >>> The TX-power limiting in ath_get_rate_txpower did not apply this shift, >>> thus retrieved the incorrect maximum power level. For example, the >>> maximum power for OFDM rate 0 was used for MCS rate 0. If STBC was used, >>> the power was mostly limited to 0 because the STBC table is zeroed for >>> legacy CCK/OFDM rates. This patch fixes this table lookup. >>> >>> Signed-off-by: Jonas Jelonek <jelonek.jonas@xxxxxxxxx> >> >> So what effect does this bug have in practice? Also, how did you test >> the patch? :) >> > > It actually may not have an effect in most of current practical applications. The > member ‘tpc_enabled' in struct ath_hw is by default set to false and thus, TPC > in ath9k is usually disabled. The code path will be skipped in that case. > But it has an effect as I am still working on TPC per packet in ath9k as part of > research. Looking at my traces I saw that the TX-power is capped at 0 for > MCS rates 0-7 in case the STBC flag is set in struct ieee80211_tx_info. Thus, > transmission was significantly worse as usual, and I also was not able to > manually set a proper TX-power via my testing API. With other rates it is working > fine. I also double-checked that it isn’t a problem of how TX-power is set and > reported with our upcoming API. > > I tested this with my OpenWrt-based AP-STA desk setup using two different > ath9k wifi chips (AR9280, AR9580), Kernel 5.15.98. I guess that should be > sufficient as ath9k hasn’t changed that significantly since that and several > changes are already backported. I compile-tested it with latest 6.3 kernel > (+allyesconfig), the patch applied flawlessly and encountered no problems. > After applying my patch, I could see that everything was working as expected. > Transmission performs equally as if TPC was disabled, and setting + reporting > TX-power was working again. Also verified this with some verbose debugging > in ath_get_rate_txpower to see which index + max power is used. Alright, cool! Could you please add all this to the commit message and resubmit? -Toke
