ath9k_hw: fix A-MPDU key search issues on AR9003

Under load, a large number of frames can produce decryption errors, even when
no key cache update is being done. Performing a key search for every single
frame in an A-MPDU improves reliability.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hw.c

@@ -1817,6 +1817,10 @@ int ath9k_hw_fill_cap_info(struct ath_hw *ah)
 
 	ah->misc_mode |= AR_PCU_MIC_NEW_LOC_ENA;
 
+	/* enable key search for every frame in an aggregate */
+	if (AR_SREV_9300_20_OR_LATER(ah))
+		ah->misc_mode |= AR_PCU_ALWAYS_PERFORM_KEYSEARCH;
+
 	pCap->low_2ghz_chan = 2312;
 	pCap->high_2ghz_chan = 2732;
 

drivers/net/wireless/ath/ath9k/reg.h

@@ -1568,6 +1568,7 @@ enum {
 #define AR_PCU_TBTT_PROTECT        0x00200000
 #define AR_PCU_CLEAR_VMF           0x01000000
 #define AR_PCU_CLEAR_BA_VALID      0x04000000
+#define AR_PCU_ALWAYS_PERFORM_KEYSEARCH 0x10000000
 
 #define AR_PCU_BT_ANT_PREVENT_RX   0x00100000
 #define AR_PCU_BT_ANT_PREVENT_RX_S 20