mac80211: add minstrel fixes that fix mt76 issues in legacy mode

Remove deferred sampling code which does not work well with rate tables +
probing.
Fix tx status handling if the first invalid rate idx is not set to -1

Signed-off-by: Felix Fietkau <nbd@nbd.name>

package/kernel/mac80211/patches/subsys/334-mac80211-minstrel-remove-deferred-sampling-code.patch

@@ -0,0 +1,96 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 11 Nov 2020 19:17:44 +0100
+Subject: [PATCH] mac80211: minstrel: remove deferred sampling code
+
+Deferring sampling attempts to the second stage has some bad interactions
+with drivers that process the rate table in hardware and use the probe flag
+to indicate probing packets (e.g. most mt76 drivers). On affected drivers
+it can lead to probing not working at all.
+
+If the link conditions turn worse, it might not be such a good idea to
+do a lot of sampling for lower rates in this case.
+
+Fix this by simply skipping the sample attempt instead of deferring it,
+but keep the checks that would allow it to be sampled if it was skipped
+too often, but only if it has less than 95% success probability.
+
+Also ensure that IEEE80211_TX_CTL_RATE_CTRL_PROBE is set for all probing
+packets.
+
+Cc: stable@vger.kernel.org
+Fixes: cccf129f820e ("mac80211: add the 'minstrel' rate control algorithm")
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel.c
++++ b/net/mac80211/rc80211_minstrel.c
+@@ -287,12 +287,6 @@ minstrel_tx_status(void *priv, struct ie
+ 			mi->r[ndx].stats.success += success;
+ 	}
+ 
+-	if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
+-		mi->sample_packets++;
+-
+-	if (mi->sample_deferred > 0)
+-		mi->sample_deferred--;
+-
+ 	if (time_after(jiffies, mi->last_stats_update +
+ 				mp->update_interval / (mp->new_avg ? 2 : 1)))
+ 		minstrel_update_stats(mp, mi);
+@@ -367,7 +361,7 @@ minstrel_get_rate(void *priv, struct iee
+ 		return;
+ 
+ 	delta = (mi->total_packets * sampling_ratio / 100) -
+-			(mi->sample_packets + mi->sample_deferred / 2);
++			mi->sample_packets;
+ 
+ 	/* delta < 0: no sampling required */
+ 	prev_sample = mi->prev_sample;
+@@ -376,7 +370,6 @@ minstrel_get_rate(void *priv, struct iee
+ 		return;
+ 
+ 	if (mi->total_packets >= 10000) {
+-		mi->sample_deferred = 0;
+ 		mi->sample_packets = 0;
+ 		mi->total_packets = 0;
+ 	} else if (delta > mi->n_rates * 2) {
+@@ -401,19 +394,8 @@ minstrel_get_rate(void *priv, struct iee
+ 	 * rate sampling method should be used.
+ 	 * Respect such rates that are not sampled for 20 interations.
+ 	 */
+-	if (mrr_capable &&
+-	    msr->perfect_tx_time > mr->perfect_tx_time &&
+-	    msr->stats.sample_skipped < 20) {
+-		/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
+-		 * packets that have the sampling rate deferred to the
+-		 * second MRR stage. Increase the sample counter only
+-		 * if the deferred sample rate was actually used.
+-		 * Use the sample_deferred counter to make sure that
+-		 * the sampling is not done in large bursts */
+-		info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
+-		rate++;
+-		mi->sample_deferred++;
+-	} else {
++	if (msr->perfect_tx_time < mr->perfect_tx_time ||
++	    msr->stats.sample_skipped >= 20) {
+ 		if (!msr->sample_limit)
+ 			return;
+ 
+@@ -433,6 +415,7 @@ minstrel_get_rate(void *priv, struct iee
+ 
+ 	rate->idx = mi->r[ndx].rix;
+ 	rate->count = minstrel_get_retry_count(&mi->r[ndx], info);
++	info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
+ }
+ 
+ 
+--- a/net/mac80211/rc80211_minstrel.h
++++ b/net/mac80211/rc80211_minstrel.h
+@@ -126,7 +126,6 @@ struct minstrel_sta_info {
+ 	u8 max_prob_rate;
+ 	unsigned int total_packets;
+ 	unsigned int sample_packets;
+-	int sample_deferred;
+ 
+ 	unsigned int sample_row;
+ 	unsigned int sample_column;

package/kernel/mac80211/patches/subsys/335-mac80211-minstrel-fix-tx-status-processing-corner-ca.patch

@@ -0,0 +1,26 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 11 Nov 2020 19:25:39 +0100
+Subject: [PATCH] mac80211: minstrel: fix tx status processing corner case
+
+Some drivers fill the status rate list without setting the rate index after
+the final rate to -1. minstrel_ht already deals with this, but minstrel
+doesn't, which causes it to get stuck at the lowest rate on these drivers.
+
+Fix this by checking the count as well.
+
+Cc: stable@vger.kernel.org
+Fixes: cccf129f820e ("mac80211: add the 'minstrel' rate control algorithm")
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel.c
++++ b/net/mac80211/rc80211_minstrel.c
+@@ -274,7 +274,7 @@ minstrel_tx_status(void *priv, struct ie
+ 	success = !!(info->flags & IEEE80211_TX_STAT_ACK);
+ 
+ 	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
+-		if (ar[i].idx < 0)
++		if (ar[i].idx < 0 || !ar[i].count)
+ 			break;
+ 
+ 		ndx = rix_to_ndx(mi, ar[i].idx);