Currently, ACS computation triggers when ACS scan complete event is
received after firmware has scanned all channels. This leads to
delay in selection on SAP channel.
As an optimization, this change selects the first clean channel
while scan is still in progress. The criteria for first clean channel
is that no beacon/probe response should be received on that channel.
If such channel is obtained while scan is in progress, then select this
channel as SAP channel and abort ongoing scan. Firmware sends
wma_chan_info_event per channel this change uses this event as an
indication that scan is completed on that channel.
To further increase the optimize the time to get clean channel, sort the
ACS frequency list in descending order in ACS SCAN request to
firmware. Firmware scans the channel in the order given by host
in scan request, as higher band channels are less occupied, the
probability of getting clean channel initially will increase, which
will lead to selecting the channel in less time and thereby reduce
the SAP turn on time.
Change-Id: I1a38556862b66943edea08783436f5e1e3a255f6
CRs-Fixed: 3245166
ef08e7a4c4