tree afcc245bb6b9b7b01c4f336426f41f876cdee287
parent 8e2de74e781e696636e8b4cd08084d2b310d44d9
author Juuso Oikarinen <juuso.oikarinen@nokia.com> 1295848914 +0100
committer Luciano Coelho <coelho@ti.com> 1295904873 +0200

wl12xx: Increase scan channel dwell time for passive scans

The passive scan channel dwell time currently used is 30-60TU. A typical
beacon interval for AP's is 100TU. This leads to a ~30% worst-case probability
of finding an AP via passive scanning.

For 5GHz bands for DFS frequencies passive scanning is the only scanning
option. Hence for these, the probability of finding an AP is very low.

To fix this, increase the passive channel scan dwell times (also the early
leave value, as 5GHz channels are still typically very silent.) Use a value
of 100TU, because that covers most typical AP configurations.

Based on testing the probability of finding an AP (100TU beacon interval) on
a single scan round are as follows (based on 100 iterations):

dwell min/max (TU)   | probability
---------------------+------------
30/60                | 35%
60/60                | 56%
80/80                | 77%
100/100              | 100%

Total scan times now and after the change:

Region | Before (s) | After (s)
-------+------------+----------
00     | 0.77       | 1.48
FI     | 0.95       | 2.01
US     | 0.91       | 1.76

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>