ath9k_hw: Fix signal strength / channel noise reporting

While AR_PHY_CCA_NOM_VAL_* does contain the expected internal noise floor
for a chip measured in clean air, it refers to the lowest expected reading.

Depending on the frequency, this measurement can vary by about 6db, thus
causing a higher reported channel noise and signal strength.

Factor in the 6db offset when converting internal noisefloor to channel noise.

This patch makes the reported values more accurate for all chips without
affecting NF calibration behavior.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/ath9k/calib.c b/drivers/net/wireless/ath/ath9k/calib.c
index f3448a032e6f377cb52154975369af7cb21aa316..1e8508530e984487cfce4aba50df5e6af8b0873b 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/calib.c
+++ b/drivers/net/wireless/ath/ath9k/calib.c
@@ -69,6 +69,7 @@ s16 ath9k_hw_getchan_noise(struct ath_hw *ah, struct ath9k_channel *chan)
 
        if (chan && chan->noisefloor) {
                s8 delta = chan->noisefloor -
+                          ATH9K_NF_CAL_NOISE_THRESH -
                           ath9k_hw_get_default_nf(ah, chan);
                if (delta > 0)
                        noise += delta;

diff --git a/drivers/net/wireless/ath/ath9k/calib.h b/drivers/net/wireless/ath/ath9k/calib.h
index 1060c19a50129a2f8a2e94a4d4fd331e0ebc85e7..60dcb6c22db91032a859b3f110c22fb3258d7817 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/calib.h
+++ b/drivers/net/wireless/ath/ath9k/calib.h
@@ -21,6 +21,9 @@
 
 #define AR_PHY_CCA_FILTERWINDOW_LENGTH          5
 
+/* Internal noise floor can vary by about 6db depending on the frequency */
+#define ATH9K_NF_CAL_NOISE_THRESH              6
+
 #define NUM_NF_READINGS       6
 #define ATH9K_NF_CAL_HIST_MAX 5