Re: [PATCH ath-next] wifi: ath12k: Fix the assignment of logical link index

[Baochen Qiang <baochen.qiang@oss.qualcomm.com>]

On 2/26/2026 12:19 PM, Roopni Devanathan wrote:
> From: Manish Dharanenthiran <manish.dharanenthiran@oss.qualcomm.com>
> 
> Per-link logical index is assigned from the global counter,
> ahsta->num_peer. This logical index is sent to firmware during peer
> association. If there is a failure in creating a link station,
> ath12k_mac_free_unassign_link_sta() clears the link, but does not decrement
> the logical link index. This will result in a higher logical link index for
> the next link station created. Also, if there is a leak in logical link
> index as we assign the incremented num_peer, then the index can exceed the
> maximum valid value of 15.
> 
> As an example, let's say we have a 2 GHz + 5 GHz + 6 GHz MLO setup. So the
> logical link indices that they have are 0, 1 and 2, respectively. If the
> 5 GHz link is removed, logical link index 1 becomes available, and num_peer
> is not reduced to 2 and still remains at 3. If a new 5 GHz link is added
> later, it gets the index 3, instead of reusing link index 1. Also,
> num_peer is increased to 4, though only 3 links are present.
> 
> To resolve these, create a bitmap, free_logical_link_idx, that tracks the
> available logical link indices. When a link station is created, select the
> first free logical index and when a link station is removed, mark its
> logical link index as available by setting the bit.
> 
> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01181-QCAHKSWPL_SILICONZ-1
> 
> Signed-off-by: Manish Dharanenthiran <manish.dharanenthiran@oss.qualcomm.com>
> Signed-off-by: Roopni Devanathan <roopni.devanathan@oss.qualcomm.com>
> ---
>  drivers/net/wireless/ath/ath12k/core.h |  2 +-
>  drivers/net/wireless/ath/ath12k/mac.c  | 16 ++++++++++++++--
>  2 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath12k/core.h b/drivers/net/wireless/ath/ath12k/core.h
> index 990934ec92fc..5498ff285102 100644
> --- a/drivers/net/wireless/ath/ath12k/core.h
> +++ b/drivers/net/wireless/ath/ath12k/core.h
> @@ -522,7 +522,7 @@ struct ath12k_sta {
>  	u16 links_map;
>  	u8 assoc_link_id;
>  	u16 ml_peer_id;
> -	u8 num_peer;
> +	u16 free_logical_link_idx_map;
>  
>  	enum ieee80211_sta_state state;
>  };
> diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
> index 68431a0e128e..db1b098b67d0 100644
> --- a/drivers/net/wireless/ath/ath12k/mac.c
> +++ b/drivers/net/wireless/ath/ath12k/mac.c
> @@ -6784,6 +6784,8 @@ static void ath12k_mac_free_unassign_link_sta(struct ath12k_hw *ah,
>  		return;
>  
>  	ahsta->links_map &= ~BIT(link_id);
> +	ahsta->free_logical_link_idx_map |= BIT(arsta->link_idx);
> +
>  	rcu_assign_pointer(ahsta->link[link_id], NULL);
>  	synchronize_rcu();
>  
> @@ -7102,6 +7104,7 @@ static int ath12k_mac_assign_link_sta(struct ath12k_hw *ah,
>  	struct ieee80211_sta *sta = ath12k_ahsta_to_sta(ahsta);
>  	struct ieee80211_link_sta *link_sta;
>  	struct ath12k_link_vif *arvif;
> +	int link_idx;
>  
>  	lockdep_assert_wiphy(ah->hw->wiphy);
>  
> @@ -7120,8 +7123,16 @@ static int ath12k_mac_assign_link_sta(struct ath12k_hw *ah,
>  
>  	ether_addr_copy(arsta->addr, link_sta->addr);
>  
> -	/* logical index of the link sta in order of creation */
> -	arsta->link_idx = ahsta->num_peer++;
> +	if (!ahsta->free_logical_link_idx_map)
> +		return -ENOSPC;
> +
> +	/*
> +	 * Allocate a logical link index by selecting the first available bit
> +	 * from the free logical index map
> +	 */
> +	link_idx = __ffs(ahsta->free_logical_link_idx_map);
> +	ahsta->free_logical_link_idx_map &= ~BIT(link_idx);
> +	arsta->link_idx = link_idx;
>  
>  	arsta->link_id = link_id;
>  	ahsta->links_map |= BIT(arsta->link_id);
> @@ -7630,6 +7641,7 @@ int ath12k_mac_op_sta_state(struct ieee80211_hw *hw,
>  	if (old_state == IEEE80211_STA_NOTEXIST &&
>  	    new_state == IEEE80211_STA_NONE) {
>  		memset(ahsta, 0, sizeof(*ahsta));
> +		ahsta->free_logical_link_idx_map = U16_MAX;
>  
>  		arsta = &ahsta->deflink;
>  
> 
> base-commit: 62f9b9b19939138c34ce0ac1e5d4969d617ecbb6

Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>