ath9k returns a wrong RSSI value for frames received in a 30ms time window after
a channel change. The correct value is typically 10dB below the returned value.

This was found with a Atheros AR9300 Rev:3 chip (WLE350NX / JWX6083 cards),
during offchannel scans.

Mark the signal value as invalid in this case.

Signed-off-by: Jean Pierre TOSONI <jp.tos...@acksys.fr>
---
 .../a995-b-acksys-ath9k-wait-channel-change.patch  |   39 ++++++++++++++++++++
 1 files changed, 39 insertions(+), 0 deletions(-)
 create mode 100644 
package/kernel/mac80211/patches/a995-b-acksys-ath9k-wait-channel-change.patch

diff --git 
a/package/kernel/mac80211/patches/a995-b-acksys-ath9k-wait-channel-change.patch 
b/package/kernel/mac80211/patches/a995-b-acksys-ath9k-wait-channel-change.patch
new file mode 100644
index 0000000..d1e1146
--- /dev/null
+++ 
b/package/kernel/mac80211/patches/a995-b-acksys-ath9k-wait-channel-change.patch
@@ -0,0 +1,39 @@
+--- a/drivers/net/wireless/ath/ath9k/ani.c
++++ b/drivers/net/wireless/ath/ath9k/ani.c
+@@ -333,6 +333,7 @@ void ath9k_ani_reset(struct ath_hw *ah,
+               return;
+ 
+       BUG_ON(aniState == NULL);
++      ah->chan_stable_time = jiffies + (30*HZ)/1000; /* 30ms */
+       ah->stats.ast_ani_reset++;
+ 
+       ofdm_nil = max_t(int, ATH9K_ANI_OFDM_DEF_LEVEL,
+--- a/drivers/net/wireless/ath/ath9k/common.c
++++ b/drivers/net/wireless/ath/ath9k/common.c
+@@ -220,6 +220,16 @@ void ath9k_cmn_process_rssi(struct ath_c
+       int i, j;
+ 
+       /*
++       * RSSI is not available before 30ms after reset on ath9k.
++       */
++      if (time_before(jiffies, ah->chan_stable_time)) {
++              ath_dbg(common, ANY, "early frame rssi=%d\n",rx_stats->rs_rssi);
++              rxs->flag |= RX_FLAG_NO_SIGNAL_VAL;
++              return;
++      }
++      ah->chan_stable_time = jiffies; /* advance stable time to cop with 
jiffies wraparound */
++
++      /*
+        * RSSI is not available for subframes in an A-MPDU.
+        */
+       if (rx_stats->rs_moreaggr) {
+--- a/drivers/net/wireless/ath/ath9k/hw.h
++++ b/drivers/net/wireless/ath/ath9k/hw.h
+@@ -816,6 +816,7 @@ struct ath_hw {
+ 
+       bool reset_power_on;
+       bool htc_reset_init;
++      unsigned long chan_stable_time;
+ 
+       enum nl80211_iftype opmode;
+       enum ath9k_power_mode power_mode;
-- 
1.7.2.5

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