ath5k: add notes about rx timestamp
add comments about the fact that we don't know when exactly the atheros
hardware takes the RX timestamp.
drivers/net/wireless/ath5k/base.c: Changes-licensed-under: 3-Clause-BSD
Signed-off-by: Bruno Randolf <bruno@thinktube.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
index 73e7e61..5eacc7c 100644
--- a/drivers/net/wireless/ath5k/base.c
+++ b/drivers/net/wireless/ath5k/base.c
@@ -1844,6 +1844,17 @@
* 15bit only. that means TSF extension has to be done within
* 32768usec (about 32ms). it might be necessary to move this to
* the interrupt handler, like it is done in madwifi.
+ *
+ * Unfortunately we don't know when the hardware takes the rx
+ * timestamp (beginning of phy frame, data frame, end of rx?).
+ * The only thing we know is that it is hardware specific...
+ * On AR5213 it seems the rx timestamp is at the end of the
+ * frame, but i'm not sure.
+ *
+ * NOTE: mac80211 defines mactime at the beginning of the first
+ * data symbol. Since we don't have any time references it's
+ * impossible to comply to that. This affects IBSS merge only
+ * right now, so it's not too bad...
*/
rxs.mactime = ath5k_extend_tsf(sc->ah, rs.rs_tstamp);
rxs.flag |= RX_FLAG_TSFT;
