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>

5 files changed, 85 insertions, 64 deletions

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index c7386b2b767e..cc11558d8c1a 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -543,30 +543,11 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
         if (ether_addr_equal(cbss->bssid, sdata->u.ibss.bssid))
                 goto put_bss;
 
-        if (rx_status->flag & RX_FLAG_MACTIME_MPDU) {
-                /*
-                 * For correct IBSS merging we need mactime; since mactime is
-                 * defined as the time the first data symbol of the frame hits
-                 * the PHY, and the timestamp of the beacon is defined as "the
-                 * time that the data symbol containing the first bit of the
-                 * timestamp is transmitted to the PHY plus the transmitting
-                 * STA's delays through its local PHY from the MAC-PHY
-                 * interface to its interface with the WM" (802.11 11.1.2)
-                 * - equals the time this bit arrives at the receiver - we have
-                 * to take into account the offset between the two.
-                 *
-                 * E.g. at 1 MBit that means mactime is 192 usec earlier
-                 * (=24 bytes * 8 usecs/byte) than the beacon timestamp.
-                 */
-                int rate;
-
-                if (rx_status->flag & RX_FLAG_HT)
-                        rate = 65; /* TODO: HT rates */
-                else
-                        rate = local->hw.wiphy->bands[band]->
-                                bitrates[rx_status->rate_idx].bitrate;
-
-                rx_timestamp = rx_status->mactime + (24 * 8 * 10 / rate);
+        if (ieee80211_have_rx_timestamp(rx_status)) {
+                /* time when timestamp field was received */
+                rx_timestamp =
+                        ieee80211_calculate_rx_timestamp(local, rx_status,
+                                                         len + FCS_LEN, 24);
         } else {
                 /*
                  * second best option: get current TSF
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index e1fb97cc9a41..bff82a8e62f3 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1259,7 +1259,18 @@ static inline int ieee80211_bssid_match(const u8 *raddr, const u8 *addr)
                is_broadcast_ether_addr(raddr);
 }
 
+static inline bool
+ieee80211_have_rx_timestamp(struct ieee80211_rx_status *status)
+{
+        WARN_ON_ONCE(status->flag & RX_FLAG_MACTIME_START &&
+                     status->flag & RX_FLAG_MACTIME_END);
+        return status->flag & (RX_FLAG_MACTIME_START | RX_FLAG_MACTIME_END);
+}
 
+u64 ieee80211_calculate_rx_timestamp(struct ieee80211_local *local,
+                                     struct ieee80211_rx_status *status,
+                                     unsigned int mpdu_len,
+                                     unsigned int mpdu_offset);
 int ieee80211_hw_config(struct ieee80211_local *local, u32 changed);
 void ieee80211_tx_set_protected(struct ieee80211_tx_data *tx);
 void ieee80211_bss_info_change_notify(struct ieee80211_sub_if_data *sdata,
diff --git a/net/mac80211/mesh_sync.c b/net/mac80211/mesh_sync.c
index 407c8705e10d..9c6ea9cfe1b3 100644
--- a/net/mac80211/mesh_sync.c
+++ b/net/mac80211/mesh_sync.c
@@ -116,43 +116,13 @@ static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
                 goto no_sync;
         }
 
-        if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
-                /*
-                 * The mactime is defined as the time the first data symbol
-                 * of the frame hits the PHY, and the timestamp of the beacon
-                 * is defined as "the time that the data symbol containing the
-                 * first bit of the timestamp is transmitted to the PHY plus
-                 * the transmitting STA's delays through its local PHY from the
-                 * MAC-PHY interface to its interface with the WM" (802.11
-                 * 11.1.2)
-                 *
-                 * T_r, in 13.13.2.2.2, is just defined as "the frame reception
-                 * time" but we unless we interpret that time to be the same
-                 * time of the beacon timestamp, the offset calculation will be
-                 * off.  Below we adjust t_r to be "the time at which the first
-                 * symbol of the timestamp element in the beacon is received".
-                 * This correction depends on the rate.
-                 *
-                 * Based on similar code in ibss.c
-                 */
-                int rate;
-
-                if (rx_status->flag & RX_FLAG_HT) {
-                        /* TODO:
-                         * In principle there could be HT-beacons (Dual Beacon
-                         * HT Operation options), but for now ignore them and
-                         * just use the primary (i.e. non-HT) beacons for
-                         * synchronization.
-                         * */
-                        goto no_sync;
-                } else
-                        rate = local->hw.wiphy->bands[rx_status->band]->
-                                bitrates[rx_status->rate_idx].bitrate;
-
-                /* 24 bytes of header * 8 bits/byte *
-                 * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
-                t_r = rx_status->mactime + (24 * 8 * 10 / rate);
-        }
+        if (ieee80211_have_rx_timestamp(rx_status))
+                /* time when timestamp field was received */
+                t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
+                                                       24 + 12 +
+                                                       elems->total_len +
+                                                       FCS_LEN,
+                                                       24);
 
         /* Timing offset calculation (see 13.13.2.2.2) */
         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 6ad330341b71..e3daee8fdf7a 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -81,7 +81,7 @@ ieee80211_rx_radiotap_len(struct ieee80211_local *local,
         /* always present fields */
         len = sizeof(struct ieee80211_radiotap_header) + 9;
 
-        if (status->flag & RX_FLAG_MACTIME_MPDU)
+        if (ieee80211_have_rx_timestamp(status))
                 len += 8;
         if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
                 len += 1;
@@ -117,6 +117,11 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
         struct ieee80211_radiotap_header *rthdr;
         unsigned char *pos;
         u16 rx_flags = 0;
+        int mpdulen;
+
+        mpdulen = skb->len;
+        if (!(has_fcs && (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS)))
+                mpdulen += FCS_LEN;
 
         rthdr = (struct ieee80211_radiotap_header *)skb_push(skb, rtap_len);
         memset(rthdr, 0, rtap_len);
@@ -134,8 +139,11 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
         /* the order of the following fields is important */
 
         /* IEEE80211_RADIOTAP_TSFT */
-        if (status->flag & RX_FLAG_MACTIME_MPDU) {
-                put_unaligned_le64(status->mactime, pos);
+        if (ieee80211_have_rx_timestamp(status)) {
+                put_unaligned_le64(
+                        ieee80211_calculate_rx_timestamp(local, status,
+                                                         mpdulen, 0),
+                        pos);
                 rthdr->it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_TSFT);
                 pos += 8;
         }
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;
+}