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Subject: Re: [PATCH v2] ath9k: fix per-packet TX-power cap for TPC
From:   Kalle Valo <kvalo@kernel.org>
In-Reply-To: <20230330132159.758088-1-jelonek.jonas@gmail.com>
References: <20230330132159.758088-1-jelonek.jonas@gmail.com>
To:     Jonas Jelonek <jelonek.jonas@gmail.com>
Cc:     linux-wireless@vger.kernel.org, thomas.huehn@hs-nordhausen.de,
        nbd@nbd.name, johannes.berg@intel.com, lorenzo@kernel.org,
        Jonas Jelonek <jelonek.jonas@gmail.com>
User-Agent: pwcli/0.1.1-git (https://github.com/kvalo/pwcli/) Python/3.7.3
Message-ID: <168172751777.21228.15075674009242455727.kvalo@kernel.org>
Date:   Mon, 17 Apr 2023 10:31:59 +0000 (UTC)
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Jonas Jelonek <jelonek.jonas@gmail.com> wrote:

> 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 currently does not apply
> this shift, thus retrieves the incorrect maximum power level for a given
> rate. In particular for MCS rates, the maximum power levels for CCK/OFDM
> rates were used, e.g. maximum power for OFDM 0 was used for MCS 0. If
> STBC is used, the power is mostly limited to 0 because the STBC table
> is zeroed for legacy CCK/OFDM rates. Encountered this during testing of
> our work-in-progress TPC per packet for ath9k.
> This only has an effect when TPC is enabled in ath9k (tpc_enabled in
> struct ath_hw) which defaults to false. In this case it has a
> significant impact on the used TX-power, throughput + RSSI. Otherwise
> the affected code is just skipped and TX-power is limited with the
> hardware registers only. This patch fixes this table lookup.
> 
> Tested on OpenWrt (kernel 5.15.98, but backported ath9k driver) with
> small desk setup using ath9k chips AR9280 and AR9580. Cap of TX-power is
> working properly for all rates now, throughput and RSSI as expected,
> equal to as if TPC was disabled.
> Compile-tested with latest 6.3 kernel + allyesconfig.
> 
> Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
> Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
> Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>

Patch applied to ath-next branch of ath.git, thanks.

e04e4b6e01e7 wifi: ath9k: fix per-packet TX-power cap for TPC

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20230330132159.758088-1-jelonek.jonas@gmail.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches