Re: [PATCH ath-next] wifi: ath12k: Fix legacy rate mapping for monitor mode capture

[Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>]

On 2/9/2026 11:19 AM, Thiraviyam Mariyappan wrote:
> From: P Praneesh <praneesh.p@oss.qualcomm.com>
> 
> The current implementation incorrectly reports legacy CCK and OFDM rates
> in monitor mode radiotap headers. The rate field displays wrong values,
> for example showing 11 Mbps when the actual rate is 1 Mbps. This occurs
> because the HAL layer uses a unified enum for both CCK and OFDM rates
> without distinguishing between long/short preamble variants and proper
> rate mapping to hardware rate indices.
> 
> The root cause is threefold:
> 
> 1. The hal_rx_legacy_rate enum conflates CCK and OFDM rates into a
>     single enumeration, making it impossible to differentiate between
>     802.11b CCK rates (with long/short preamble variants) and 802.11a/g
>     OFDM rates.
> 
> 2. The L-SIG-B parsing function maps hardware rate values to the wrong
>     enum values. For CCK rates, it incorrectly combines long and short
>     preamble cases (e.g., cases 2 and 5 both map to 2 Mbps), losing
>     preamble information critical for proper rate identification.
> 
> 3. The mac layer's rate-to-index conversion function does not properly
>     handle the precedence between long preamble, short preamble, and
>     OFDM rates when matching hardware rate values.
> 
> Split the hal_rx_legacy_rate enum into two separate enumerations:
> hal_rx_legacy_rate for CCK rates with explicit long preamble (LP) and
> short preamble (SP) variants, and hal_rx_legacy_rates_ofdm for OFDM
> rates. This separation allows proper identification of rate types and
> preamble modes.
> 
> Introduce a new mapping ath12k_wifi7_hal_mon_map_legacy_rate_to_hw_rate()
> that converts HAL CCK rate enums to hardware rate indices defined in
> ath12k_hw_rate_cck. This ensures the rate field in ppdu_info contains
> the correct hardware rate index that matches the mac layer's expectations.
> 
> Update the L-SIG-B parsing to map each hardware rate value (1-7) to its
> corresponding CCK rate enum with proper preamble designation:
> - Cases 1-4: Long preamble (1, 2, 5.5, 11 Mbps)
> - Cases 5-7: Short preamble (2, 5.5, 11 Mbps)
> 
> Update the L-SIG-A parsing to use the new OFDM-specific enum values,
> maintaining the existing rate mapping for 802.11a/g OFDM rates.
> 
> Refactor the mac layer's ath12k_mac_hw_rate_to_idx() function to
> implement proper matching precedence:
> 1. First match OFDM rates using the IEEE80211_RATE_MANDATORY_A flag
> 2. Then match CCK short preamble rates
> 3. Finally match CCK long preamble rates as fallback
> 
> Add helper macros ATH12K_MAC_RATE_A_M and ATH12K_MAC_RATE_B to improve
> readability of the rate table initialization and ensure the mandatory
> flag is set for OFDM rates.
> 
> This fix ensures monitor mode captures display accurate rate information
> in the radiotap header, correctly distinguishing between 1 Mbps and
> 11 Mbps, and properly identifying preamble types for CCK rates.
> 
> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01181-QCAHKSWPL_SILICONZ-1
> 
> Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
> Signed-off-by: P Praneesh <praneesh.p@oss.qualcomm.com>
> Signed-off-by: Thiraviyam Mariyappan <thiraviyam.mariyappan@oss.qualcomm.com>

Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>