[PATCH v3] wifi: ath12k: fix incorrect HT/VHT/HE/EHT MCS reporting in monitor mode

[kwan1996 <laicheehou9@gmail.com>]

From: Kwan Lai Chee Hou <laicheehou9@gmail.com>

In monitor mode, the driver incorrectly assigns the legacy rate
to the rate_idx field of the radiotap header for HT/VHT/HE/EHT
frames, ignoring the actual MCS value parsed from the hardware.

This causes packet analyzers (like Wireshark) to display incorrect
MCS values (e.g., legacy base rates instead of the true MCS).

Fix this by assigning ppdu_info->mcs as the default rate_mcs
in ath12k_dp_mon_fill_rx_rate(), and remove rate_idx assignments in 
ath12k_dp_mon_update_radiotap() to preserve
the previously calculated MCS values (including the HT NSS offset).

Link: https://bugzilla.kernel.org/show_bug.cgi?id=220864

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ

Signed-off-by: Kwan Lai Chee Hou <laicheehou9@gmail.com>

---
v3: 
 - Simplify rate_mcs assignment logic in ath12k_dp_mon_fill_rx_rate.
 - remove rate_idx assignments in ath12k_dp_mon_update_radiotap to avoid overwriting the HT (802.11n) MCS calculated earlier.
 
v2: Fix indentation and formatting issues in v1.
---
 drivers/net/wireless/ath/ath12k/dp_mon.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/dp_mon.c b/drivers/net/wireless/ath/ath12k/dp_mon.c
index 39d1967..79347c3 100644
--- a/drivers/net/wireless/ath/ath12k/dp_mon.c
+++ b/drivers/net/wireless/ath/ath12k/dp_mon.c
@@ -1910,13 +1910,14 @@ ath12k_dp_mon_fill_rx_rate(struct ath12k *ar,
 	bool is_cck;
 
 	pkt_type = ppdu_info->preamble_type;
-	rate_mcs = ppdu_info->rate;
+	rate_mcs = ppdu_info->mcs;
 	nss = ppdu_info->nss;
 	sgi = ppdu_info->gi;
 
 	switch (pkt_type) {
 	case RX_MSDU_START_PKT_TYPE_11A:
 	case RX_MSDU_START_PKT_TYPE_11B:
+		rate_mcs = ppdu_info->rate;
 		is_cck = (pkt_type == RX_MSDU_START_PKT_TYPE_11B);
 		if (rx_status->band < NUM_NL80211_BANDS) {
 			sband = &ar->mac.sbands[rx_status->band];
@@ -2259,13 +2260,10 @@ static void ath12k_dp_mon_update_radiotap(struct ath12k *ar,
 		rxs->encoding = RX_ENC_HE;
 		ptr = skb_push(mon_skb, sizeof(struct ieee80211_radiotap_he));
 		ath12k_dp_mon_rx_update_radiotap_he(ppduinfo, ptr);
-		rxs->rate_idx = ppduinfo->rate;
 	} else if (ppduinfo->vht_flags) {
 		rxs->encoding = RX_ENC_VHT;
-		rxs->rate_idx = ppduinfo->rate;
 	} else if (ppduinfo->ht_flags) {
 		rxs->encoding = RX_ENC_HT;
-		rxs->rate_idx = ppduinfo->rate;
 	} else {
 		rxs->encoding = RX_ENC_LEGACY;
 		sband = &ar->mac.sbands[rxs->band];
-- 
2.34.1