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mac80211: Take into account TSF adjustment latency in Toffset setpoint

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When testing mesh synchronization we observed a global TSF slowdown that
was dependent on the number of synchronized mesh stations.  This seems
to be caused by the TSF adjustment (read/write) latency.

Adding a small margin to the Toffset setpoint solved the problem.

Signed-off-by: Shinichi Hotori <hotorinn@gmail.com>
Signed-off-by: Yu Niiro <yu.niiro@gmail.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Javier Cardona 2012-04-12 14:32:23 -07:00 committed by John W. Linville
parent a802a6eba1
commit ec14bcd20f
1 changed files with 7 additions and 1 deletions
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8
net/mac80211/mesh_sync.c
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@ -24,11 +24,17 @@
*/ */
#define TOFFSET_MINIMUM_ADJUSTMENT 10 #define TOFFSET_MINIMUM_ADJUSTMENT 10
/* This is not in the standard. It is a margin added to the
* Toffset setpoint to mitigate TSF overcorrection
* introduced by TSF adjustment latency.
*/
#define TOFFSET_SET_MARGIN 20
/* This is not in the standard. It represents the maximum Toffset jump above /* This is not in the standard. It represents the maximum Toffset jump above
* which we'll invalidate the Toffset setpoint and choose a new setpoint. This * which we'll invalidate the Toffset setpoint and choose a new setpoint. This
* could be, for instance, in case a neighbor is restarted and its TSF counter * could be, for instance, in case a neighbor is restarted and its TSF counter
* reset. * reset.
* */ */
#define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */ #define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */
struct sync_method { struct sync_method {