I had a problem after awake from suspend with ath9k, wpa_supplicant and NetworkManager. After resume NetworkManager tried to connect to wifi, disconnect and again. I found this post in syslog:
wpa_supplicant[1944]: wlan0: Reject scan trigger since one is already pending
wpa_supplicant[1944]: wlan0: Failed to initiate AP scan
wpa_supplicant[1944]: wlan0: Reject scan trigger since one is already pending
wpa_supplicant[1944]: wlan0: Failed to initiate AP scan
wpa_supplicant[1944]: wlan0: Reject scan trigger since one is already pending
wpa_supplicant[1944]: wlan0: Failed to initiate AP scan
wpa_supplicant[1944]: wlan0: Reject scan trigger since one is already pending
wpa_supplicant[1944]: wlan0: Failed to initiate AP scan
wpa_supplicant[1944]: wlan0: Reject scan trigger since one is already pending
wpa_supplicant[1944]: wlan0: Failed to initiate AP scan.

I tried unload module, restart NetworkManager service, etc, but nothing of this help, except kill wpa_supplicant. I hope, this post help somebody else.