ath9k: Skip FFT reports if we are out of output buffers

There is no reason to keep processing FFT reports if there is no
space left on the relayfs buffers for the results. This saves
lots of CPU cycles, especially on normal (non-short) reports.
Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath9k/common-spectral.c

@@ -473,6 +473,24 @@ ath_cmn_copy_fft_frame(u8 *in, u8 *out, int sample_len, int sample_bytes)
 	}
 }
 
+static int
+ath_cmn_is_fft_buf_full(struct ath_spec_scan_priv *spec_priv)
+{
+	int i = 0;
+	int ret = 0;
+	struct rchan *rc = spec_priv->rfs_chan_spec_scan;
+
+	for_each_online_cpu(i)
+		ret += relay_buf_full(rc->buf[i]);
+
+	i = num_online_cpus();
+
+	if (ret == i)
+		return 1;
+	else
+		return 0;
+}
+
 /* returns 1 if this was a spectral frame, even if not handled. */
 int ath_cmn_process_fft(struct ath_spec_scan_priv *spec_priv, struct ieee80211_hdr *hdr,
 		    struct ath_rx_status *rs, u64 tsf)
@@ -509,6 +527,16 @@ int ath_cmn_process_fft(struct ath_spec_scan_priv *spec_priv, struct ieee80211_h
 	if (!(radar_info->pulse_bw_info & SPECTRAL_SCAN_BITMASK))
 		return 0;
 
+	/* Output buffers are full, no need to process anything
+	 * since there is no space to put the result anyway
+	 */
+	ret = ath_cmn_is_fft_buf_full(spec_priv);
+	if (ret == 1) {
+		ath_dbg(common, SPECTRAL_SCAN, "FFT report ignored, no space "
+						"left on output buffers\n");
+		return 1;
+	}
+
 	chan_type = cfg80211_get_chandef_type(&common->hw->conf.chandef);
 	if ((chan_type == NL80211_CHAN_HT40MINUS) ||
 	    (chan_type == NL80211_CHAN_HT40PLUS)) {