wcn36xx: Add SNR reporting via get_survey()

Add support for get_survey() reporting. Current channel and noise-floor are
reported, other parameters such as scan, busy, TX and RX time are not
immediately available.

Noise is a useful metric to report, so bring it out now.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220115001646.3981501-5-bryan.odonoghue@linaro.org

drivers/net/wireless/ath/wcn36xx/main.c

@@ -1357,6 +1357,49 @@ static void wcn36xx_flush(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	}
 }
 
+static int wcn36xx_get_survey(struct ieee80211_hw *hw, int idx,
+			      struct survey_info *survey)
+{
+	struct wcn36xx *wcn = hw->priv;
+	struct ieee80211_supported_band *sband;
+	struct wcn36xx_chan_survey *chan_survey;
+	int band_idx;
+	unsigned long flags;
+
+	sband = wcn->hw->wiphy->bands[NL80211_BAND_2GHZ];
+	band_idx = idx;
+	if (band_idx >= sband->n_channels) {
+		band_idx -= sband->n_channels;
+		sband = wcn->hw->wiphy->bands[NL80211_BAND_5GHZ];
+	}
+
+	if (!sband || band_idx >= sband->n_channels)
+		return -ENOENT;
+
+	spin_lock_irqsave(&wcn->survey_lock, flags);
+
+	chan_survey = &wcn->chan_survey[idx];
+	survey->channel = &sband->channels[band_idx];
+	survey->noise = chan_survey->rssi - chan_survey->snr;
+	survey->filled = 0;
+
+	if (chan_survey->rssi > -100 && chan_survey->rssi < 0)
+		survey->filled |= SURVEY_INFO_NOISE_DBM;
+
+	if (survey->channel == wcn->channel)
+		survey->filled |= SURVEY_INFO_IN_USE;
+
+	spin_unlock_irqrestore(&wcn->survey_lock, flags);
+
+	 wcn36xx_dbg(WCN36XX_DBG_MAC,
+		     "ch %d rssi %d snr %d noise %d filled %x freq %d\n",
+		     HW_VALUE_CHANNEL(survey->channel->hw_value),
+		     chan_survey->rssi, chan_survey->snr, survey->noise,
+		     survey->filled, survey->channel->center_freq);
+
+	return 0;
+}
+
 static const struct ieee80211_ops wcn36xx_ops = {
 	.start			= wcn36xx_start,
 	.stop			= wcn36xx_stop,
@@ -1385,6 +1428,7 @@ static const struct ieee80211_ops wcn36xx_ops = {
 	.ipv6_addr_change	= wcn36xx_ipv6_addr_change,
 #endif
 	.flush			= wcn36xx_flush,
+	.get_survey		= wcn36xx_get_survey,
 
 	CFG80211_TESTMODE_CMD(wcn36xx_tm_cmd)
 };