mac80211: support RX_FLAG_MACTIME_END

Allow drivers to indicate their mactime is at RX completion and adjust
for this in mac80211. Also rename the existing RX_FLAG_MACTIME_MPDU to
RX_FLAG_MACTIME_START to clarify its intent. Based on similar code by
Johannes Berg.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
[fix docs, atheros drivers]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 4e4f58513673..5bad758abfb3 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -2013,3 +2013,54 @@ u8 ieee80211_mcs_to_chains(const struct ieee80211_mcs_info *mcs)
 		return 2;
 	return 1;
 }
+
+/**
+ * ieee80211_calculate_rx_timestamp - calculate timestamp in frame
+ * @local: mac80211 hw info struct
+ * @status: RX status
+ * @mpdu_len: total MPDU length (including FCS)
+ * @mpdu_offset: offset into MPDU to calculate timestamp at
+ *
+ * This function calculates the RX timestamp at the given MPDU offset, taking
+ * into account what the RX timestamp was. An offset of 0 will just normalize
+ * the timestamp to TSF at beginning of MPDU reception.
+ */
+u64 ieee80211_calculate_rx_timestamp(struct ieee80211_local *local,
+				     struct ieee80211_rx_status *status,
+				     unsigned int mpdu_len,
+				     unsigned int mpdu_offset)
+{
+	u64 ts = status->mactime;
+	struct rate_info ri;
+	u16 rate;
+
+	if (WARN_ON(!ieee80211_have_rx_timestamp(status)))
+		return 0;
+
+	memset(&ri, 0, sizeof(ri));
+
+	/* Fill cfg80211 rate info */
+	if (status->flag & RX_FLAG_HT) {
+		ri.mcs = status->rate_idx;
+		ri.flags |= RATE_INFO_FLAGS_MCS;
+		if (status->flag & RX_FLAG_40MHZ)
+			ri.flags |= RATE_INFO_FLAGS_40_MHZ_WIDTH;
+		if (status->flag & RX_FLAG_SHORT_GI)
+			ri.flags |= RATE_INFO_FLAGS_SHORT_GI;
+	} else {
+		struct ieee80211_supported_band *sband;
+
+		sband = local->hw.wiphy->bands[status->band];
+		ri.legacy = sband->bitrates[status->rate_idx].bitrate;
+	}
+
+	rate = cfg80211_calculate_bitrate(&ri);
+
+	/* rewind from end of MPDU */
+	if (status->flag & RX_FLAG_MACTIME_END)
+		ts -= mpdu_len * 8 * 10 / rate;
+
+	ts += mpdu_offset * 8 * 10 / rate;
+
+	return ts;
+}