wifi: iwlwifi: mvm: implement link grading

For selecting what link(s) out of the usable ones
to activate, calculate a grade for a given link.

Calculation of a link grade is done as follows:
1. get the estimated throughput according to the RSSI of the link, this
   will be the base grade
2. get the channel load from the BSS Load Element, subtracting the load
   caused by us. Apply the factor on the grade.
3. puncturing factor: calculate the percentage of the punctured
   subchannels (out of the total subchannels). Apply this on the grade.

The link grading will be used by the link selection mechanism in a later
patch.

Also add KUnit tests for it.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Link: https://msgid.link/20240416134215.a6799dbd5643.If137ca6dc443606c7d8c99ec1fc38b325003a7c1@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 172 insertions, 0 deletions

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/link.c b/drivers/net/wireless/intel/iwlwifi/mvm/link.c
index 9f69e04594e4..23660238348b 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/link.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/link.c
@@ -329,3 +329,175 @@ int iwl_mvm_disable_link(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 
 	return ret;
 }
+
+struct iwl_mvm_rssi_to_grade {
+	s8 rssi[2];
+	u16 grade;
+};
+
+#define RSSI_TO_GRADE_LINE(_lb, _hb_uhb, _grade) \
+	{ \
+		.rssi = {_lb, _hb_uhb}, \
+		.grade = _grade \
+	}
+
+/*
+ * This array must be sorted by increasing RSSI for proper functionality.
+ * The grades are actually estimated throughput, represented as fixed-point
+ * with a scale factor of 1/10.
+ */
+static const struct iwl_mvm_rssi_to_grade rssi_to_grade_map[] = {
+	RSSI_TO_GRADE_LINE(-85, -89, 177),
+	RSSI_TO_GRADE_LINE(-83, -86, 344),
+	RSSI_TO_GRADE_LINE(-82, -85, 516),
+	RSSI_TO_GRADE_LINE(-80, -83, 688),
+	RSSI_TO_GRADE_LINE(-77, -79, 1032),
+	RSSI_TO_GRADE_LINE(-73, -76, 1376),
+	RSSI_TO_GRADE_LINE(-70, -74, 1548),
+	RSSI_TO_GRADE_LINE(-69, -72, 1750),
+	RSSI_TO_GRADE_LINE(-65, -68, 2064),
+	RSSI_TO_GRADE_LINE(-61, -66, 2294),
+	RSSI_TO_GRADE_LINE(-58, -61, 2580),
+	RSSI_TO_GRADE_LINE(-55, -58, 2868),
+	RSSI_TO_GRADE_LINE(-46, -55, 3098),
+	RSSI_TO_GRADE_LINE(-43, -54, 3442)
+};
+
+#define MAX_GRADE (rssi_to_grade_map[ARRAY_SIZE(rssi_to_grade_map) - 1].grade)
+
+#define DEFAULT_CHAN_LOAD_LB	30
+#define DEFAULT_CHAN_LOAD_HB	15
+#define DEFAULT_CHAN_LOAD_UHB	0
+
+/* Factors calculation is done with fixed-point with a scaling factor of 1/256 */
+#define SCALE_FACTOR 256
+
+/* Convert a percentage from [0,100] to [0,255] */
+#define NORMALIZE_PERCENT_TO_255(percentage) ((percentage) * SCALE_FACTOR / 100)
+
+static unsigned int
+iwl_mvm_get_puncturing_factor(const struct ieee80211_bss_conf *link_conf)
+{
+	enum nl80211_chan_width chan_width =
+		link_conf->chanreq.oper.width;
+	int mhz = nl80211_chan_width_to_mhz(chan_width);
+	unsigned int n_subchannels, n_punctured, puncturing_penalty;
+
+	if (WARN_ONCE(mhz < 20 || mhz > 320,
+		      "Invalid channel width : (%d)\n", mhz))
+		return SCALE_FACTOR;
+
+	/* No puncturing, no penalty */
+	if (mhz < 80)
+		return SCALE_FACTOR;
+
+	/* total number of subchannels */
+	n_subchannels = mhz / 20;
+	/* how many of these are punctured */
+	n_punctured = hweight16(link_conf->chanreq.oper.punctured);
+
+	puncturing_penalty = n_punctured * SCALE_FACTOR / n_subchannels;
+	return SCALE_FACTOR - puncturing_penalty;
+}
+
+static unsigned int
+iwl_mvm_get_chan_load_factor(struct ieee80211_bss_conf *link_conf)
+{
+	struct iwl_mvm_vif_link_info *mvm_link =
+		iwl_mvm_vif_from_mac80211(link_conf->vif)->link[link_conf->link_id];
+	const struct element *bss_load_elem =
+		ieee80211_bss_get_elem(link_conf->bss, WLAN_EID_QBSS_LOAD);
+	const struct ieee80211_bss_load_elem *bss_load;
+	enum nl80211_band band = link_conf->chanreq.oper.chan->band;
+	unsigned int chan_load;
+	u32 chan_load_by_us;
+
+	/* If there isn't BSS Load element, take the defaults */
+	if (!bss_load_elem ||
+	    bss_load_elem->datalen != sizeof(*bss_load)) {
+		switch (band) {
+		case NL80211_BAND_2GHZ:
+			chan_load = DEFAULT_CHAN_LOAD_LB;
+			break;
+		case NL80211_BAND_5GHZ:
+			chan_load = DEFAULT_CHAN_LOAD_HB;
+			break;
+		case NL80211_BAND_6GHZ:
+			chan_load = DEFAULT_CHAN_LOAD_UHB;
+			break;
+		default:
+			chan_load = 0;
+			break;
+		}
+		/* The defaults are given in percentage */
+		return SCALE_FACTOR - NORMALIZE_PERCENT_TO_255(chan_load);
+	}
+
+	bss_load = (const void *)bss_load_elem->data;
+	/* Channel util is in range 0-255 */
+	chan_load = bss_load->channel_util;
+
+	if (!mvm_link || !mvm_link->active)
+		goto done;
+
+	if (WARN_ONCE(!mvm_link->phy_ctxt,
+		      "Active link (%u) without phy ctxt assigned!\n",
+		      link_conf->link_id))
+		goto done;
+
+	/* channel load by us is given in percentage */
+	chan_load_by_us =
+		NORMALIZE_PERCENT_TO_255(mvm_link->phy_ctxt->channel_load_by_us);
+
+	/* Use only values that firmware sends that can possibly be valid */
+	if (chan_load_by_us <= chan_load)
+		chan_load -= chan_load_by_us;
+done:
+	return  SCALE_FACTOR - chan_load;
+}
+
+/* This function calculates the grade of a link. Returns 0 in error case */
+unsigned int iwl_mvm_get_link_grade(struct ieee80211_bss_conf *link_conf)
+{
+	enum nl80211_band band;
+	int i, rssi_idx;
+	s32 link_rssi;
+	unsigned int grade = MAX_GRADE;
+
+	if (WARN_ON_ONCE(!link_conf))
+		return 0;
+
+	band = link_conf->chanreq.oper.chan->band;
+	if (WARN_ONCE(band != NL80211_BAND_2GHZ &&
+		      band != NL80211_BAND_5GHZ &&
+		      band != NL80211_BAND_6GHZ,
+		      "Invalid band (%u)\n", band))
+		return 0;
+
+	link_rssi = MBM_TO_DBM(link_conf->bss->signal);
+	/*
+	 * For 6 GHz the RSSI of the beacons is lower than
+	 * the RSSI of the data.
+	 */
+	if (band == NL80211_BAND_6GHZ)
+		link_rssi += 4;
+
+	rssi_idx = band == NL80211_BAND_2GHZ ? 0 : 1;
+
+	/* Get grade based on RSSI */
+	for (i = 0; i < ARRAY_SIZE(rssi_to_grade_map); i++) {
+		const struct iwl_mvm_rssi_to_grade *line =
+			&rssi_to_grade_map[i];
+
+		if (link_rssi > line->rssi[rssi_idx])
+			continue;
+		grade = line->grade;
+		break;
+	}
+
+	/* apply the channel load and puncturing factors */
+	grade = grade * iwl_mvm_get_chan_load_factor(link_conf) / SCALE_FACTOR;
+	grade = grade * iwl_mvm_get_puncturing_factor(link_conf) / SCALE_FACTOR;
+	return grade;
+}
+EXPORT_SYMBOL_IF_IWLWIFI_KUNIT(iwl_mvm_get_link_grade);