wifi: ath12k: allow peer_id 0 in dp peer lookup

For some chipsets, firmware can report HTT_T2H_MSG_TYPE_PEER_MAP2 with
peer_id 0 as a valid value for mapping ath12k_dp_link_peer to
ath12k_dp_peer.

ath12k_dp_peer_find_by_peerid() currently treats peer_id 0 as invalid.
When firmware assigns peer_id 0, peer lookup fails. As a result,
DHCP OFFER packets are dropped in __ieee80211_rx_handle_packet()
because pubsta is NULL.

ath12k_dp_rx_deliver_msdu() <- rx_info->peer_id 0
  ath12k_dp_peer_find_by_peerid -> peer NULL
  ieee80211_rx_napi <- pubsta NULL
    ieee80211_rx_list
      __ieee80211_rx_handle_packet <- pubsta NULL, skb undelivered

The following error in the TX completion path is caused by the same issue:

ath12k_wifi7_pci 0000:04:00.0: dp_tx: failed to find the peer with peer_id 0

The error message is triggered by:
ath12k_wifi7_dp_tx_complete_msdu
  ath12k_dp_link_peer_find_by_peerid <- ts->peer_id 0
    ath12k_dp_peer_find_by_peerid -> peer NULL

ath12k_dp_tx_htt_tx_complete_buf
  ath12k_dp_link_peer_find_by_peerid <- peer_id 0
    ath12k_dp_peer_find_by_peerid -> peer NULL

Fix this by allowing peer_id 0 in ath12k_dp_peer_find_by_peerid() and
rejecting only values >= ATH12K_DP_PEER_ID_INVALID.

Also update peer_id 0 handling in monitor path:
Always call ath12k_dp_link_peer_find_by_peerid() in
ath12k_dp_rx_h_find_link_peer() to fetch the peer, including when
peer_id is 0.
Always store peer_id in ppdu_info->peer_id in
ath12k_wifi7_dp_mon_rx_parse_status_tlv(), including peer_id 0.

Tested-on: QCC2072 hw1.0 PCI WLAN.COL.1.0.c2-00074-QCACOLSWPL_V1_TO_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c7-00108-QCAHMTSWPL_V1.0_V2.0_SILICONZ_UPSTREAM-3
Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01243-QCAHKSWPL_SILICONZ-1

Signed-off-by: Hangtian Zhu <hangtian.zhu@oss.qualcomm.com>
Reviewed-by: Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Link: https://patch.msgid.link/20260512025732.1297849-1-hangtian.zhu@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>

Author: zhuhangtian

drivers/net/wireless/ath/ath12k/dp_peer.c

@@ -419,7 +419,7 @@ struct ath12k_dp_peer *ath12k_dp_peer_find_by_peerid(struct ath12k_pdev_dp *dp_p
 	RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
 			 "ath12k dp peer find by peerid index called without rcu lock");
 
-	if (!peer_id || peer_id >= ATH12K_DP_PEER_ID_INVALID)
+	if (peer_id >= ATH12K_DP_PEER_ID_INVALID)
 		return NULL;
 
 	index = ath12k_dp_peer_get_peerid_index(dp, peer_id);

drivers/net/wireless/ath/ath12k/dp_rx.c

@@ -1202,8 +1202,7 @@ ath12k_dp_rx_h_find_link_peer(struct ath12k_pdev_dp *dp_pdev, struct sk_buff *ms
 
 	lockdep_assert_held(&dp->dp_lock);
 
-	if (rxcb->peer_id)
-		peer = ath12k_dp_link_peer_find_by_peerid(dp_pdev, rxcb->peer_id);
+	peer = ath12k_dp_link_peer_find_by_peerid(dp_pdev, rxcb->peer_id);
 
 	if (peer)
 		return peer;

drivers/net/wireless/ath/ath12k/wifi7/dp_mon.c

@@ -1779,8 +1779,7 @@ ath12k_wifi7_dp_mon_rx_parse_status_tlv(struct ath12k_pdev_dp *dp_pdev,
 
 		info[1] = __le32_to_cpu(mpdu_start->info1);
 		peer_id = u32_get_bits(info[1], HAL_RX_MPDU_START_INFO1_PEERID);
-		if (peer_id)
-			ppdu_info->peer_id = peer_id;
+		ppdu_info->peer_id = peer_id;
 
 		ppdu_info->mpdu_len += u32_get_bits(info[1],
 						    HAL_RX_MPDU_START_INFO2_MPDU_LEN);