Commit ec14bcd2 authored Apr 12, 2012 by Javier Cardona Committed by John W. Linville Apr 16, 2012

mac80211: Take into account TSF adjustment latency in Toffset setpoint



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>

parent a802a6eb

net/mac80211/mesh_sync.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -24,11 +24,17 @@
		*/
		#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
		* 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
		* reset.
		* */
		*/
		#define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */

		struct sync_method {

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