Re: [PATCH 2/2] iwlwifi: RX signal improvements.

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2022-02-25 at 15:28 -0800, greearb@candelatech.com wrote:
> 
> -	if (mvmsta->avg_energy) {
> -		sinfo->signal_avg = -(s8)mvmsta->avg_energy;
> +	if (iwl_mvm_has_new_rx_api(mvm)) { /* rxmq logic */
> +		/* Grab chain signal avg, mac80211 cannot do it because
> +		 * this driver uses RSS.  Grab signal_avg here too because firmware
> +		 * appears go not do DB summing and/or has other bugs. --Ben
> +		 */

That "--Ben" really seems inappropriate ... please take more care when
sending patches to the list.

>  		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_SIGNAL_AVG);
> +		sinfo->signal_avg = -ewma_signal_read(&mvmsta->rx_avg_signal);
> +
> +		if (!mvmvif->bf_data.bf_enabled) {
> +			/* The firmware reliably reports different signal (2db weaker in my case)


dB, but I guess we'll want to fix that instead or so ...

> +static inline int iwl_mvm_sum_sigs_2(int a, int b)
> +{

Feels like that calls for a helper function somewhere else, and a
comment explaining it :)

> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c
> @@ -278,14 +278,26 @@ static void iwl_mvm_pass_packet_to_mac80211(struct iwl_mvm *mvm,
>  static void iwl_mvm_get_signal_strength(struct iwl_mvm *mvm,
>  					struct ieee80211_rx_status *rx_status,
>  					u32 rate_n_flags, int energy_a,
> -					int energy_b)
> +					int energy_b, struct ieee80211_sta *sta,
> +					bool is_beacon, bool my_beacon)
>  {
>  	int max_energy;
>  	u32 rate_flags = rate_n_flags;
> +	struct iwl_mvm_sta *mvmsta = NULL;
> +
> +	if (sta && !(is_beacon && !my_beacon)) {
> +		mvmsta = iwl_mvm_sta_from_mac80211(sta);
> +		if (energy_a)
> +			ewma_signal_add(&mvmsta->rx_avg_chain_signal[0], energy_a);
> +		if (energy_b)
> +			ewma_signal_add(&mvmsta->rx_avg_chain_signal[1], energy_b);
> +	}

This is obviously racy for the exact same reason that mac80211 doesn't
give you averages ... you cannot do that.

Without locking, you have to rely on the firmware, and I don't think we
want any locking here.

> @@ -295,6 +307,15 @@ static void iwl_mvm_get_signal_strength(struct iwl_mvm *mvm,
>  		(rate_flags & RATE_MCS_ANT_AB_MSK) >> RATE_MCS_ANT_POS;
>  	rx_status->chain_signal[0] = energy_a;
>  	rx_status->chain_signal[1] = energy_b;
> +
> +	if (mvmsta) {
> +		if (is_beacon) {
> +			if (my_beacon)
> +				ewma_signal_add(&mvmsta->rx_avg_beacon_signal, -max_energy);
> +		} else {
> +			ewma_signal_add(&mvmsta->rx_avg_signal, -max_energy);
> +		}
> +	}

Why would you ignore "is_beacon && !my_beacon" cases, but handle all
other management frames from everyone?

> @@ -1878,6 +1899,16 @@ void iwl_mvm_rx_mpdu_mq(struct iwl_mvm *mvm, struct napi_struct *napi,
>  		goto out;
>  	}
>  
> +	is_beacon = ieee80211_is_beacon(hdr->frame_control);
> +	if (is_beacon && sta) {
> +		/* see if it is beacon destined for us */
> +		if (memcmp(sta->addr, hdr->addr2, ETH_ALEN) == 0)
> +			my_beacon = true;

don't use memcmp() for that.


Anyway this really needs a lot of work, it cannot work as is.

johannes