• dev
• ath_hal(4)
• LocationReport

Location reporting

| Driver | HAL | Supported Hardware | 802.11n support | Debugging |

The AR9380 and later devices support a "time of flight" feature which can be used to estimate the distance between devices.

Overview

This is in note form for now!

• there's a separate location timer register and control register
• the counter is fed from the mac clock, so 44MHz in 20MHz wide operation, and 88MHz in 40MHz operation
• a specific bit is set for a TX frame, which causes the full packet exchange to be returned
• right now the only way to get the location timestamp is to enable the location timer, which causes /all/ frames to be timestamped with the location timestamp - ie, the TX/RX descriptor timestamps are no longer TSF.

The normal way this happens is:

• fire off a TX frame with location_mode=1, not_sounding=0
• get an RX frame (ACK) with the more bit set
• .. and the second frame in the set is the sounding data with the rate, timestamp, etc and the payload is the CSI.

Implementation

Descriptor example

[1467602208.961128] [100500] TXD DescId=0x061b
  DescLen=23, TxQcuNum=1, CtrlStat=1, DescId=0x168c
    Link 0x00000000
    Data0 0x9f1055e0 Len 28
    Data1 0x00000000 Len 0
    Data2 0x00000000 Len 0
    Data3 0x00000000 Len 0
    Desc ID=0x061b, Chksum=0xccb0 (ctl10=0x061bccb0)
    Frame Len=30, VMF=0, LowRxChain=0, TxClrRetry=0
    TX power 0 = 60, RtsEna=0, Veol=0, ClrDstMask=0
    TxIntrReq=0, DestIdxValid=1, CtsEnable=0
    Paprd Chain Mask=0x0, TxMore=0, DestIdx=4, FrType=0x0
    NoAck=0, InsertTs=0, CorruptFcs=0, ExtOnly=0, ExtAndCtl=0
    IsAggr=0, MoreRifs=0, LocMode=1
    DurUpEna=1, Burstdur=0x0000
    Try0=4, Try1=3, Try2=4, Try3=2
    rate0=0x8c, rate1=0x8b, rate2=0x8a, rate3=0x88
    try 0: PktDur=44, RTS/CTS ena=0
    try 1: PktDur=48, RTS/CTS ena=0
    try 2: PktDur=48, RTS/CTS ena=0
    try 3: PktDur=62, RTS/CTS ena=0
    AggrLen=0, PadDelim=0, EncrType=0, TxDcApStaSel=0
    Calib=0 LDPC=1
    try 0: chainMask=0x7, GI=1, 2040=0, STBC=0
    try 1: chainMask=0x7, GI=1, 2040=0, STBC=0
    try 2: chainMask=0x7, GI=1, 2040=0, STBC=0
    try 3: chainMask=0x7, GI=1, 2040=0, STBC=0
    NotSounding=1
    try 0: ant=0x00000000, antsel=0, ness=0
    try 1: TxPower=0, ant=0x00000000, antsel=0, ness=0
    try 2: TxPower=0, ant=0x00000000, antsel=0, ness=0
    try 3: TxPower=0, ant=0x00000000, antsel=0, ness=0

 ------
[1467602208.961131] [100500] TXPUSH txq=1, nframes=1, fifodepth=1, frmcount=1
[1467602208.961164] [100142] INTR: status=0x00000040
[1467602208.961320] [100142] INTR: status=0x00000042
[1467602208.961330] [100142] RXSTATUS
    RSSI 0/0/0 / 0/0/0; combined: 0; rate=0x00
    Len: 14; more=1, delim=0, upload=0
    RX timestamp: 0
    GI: 0, 2040: 0, parallel40: 0, stbc=0
    Not sounding: 0, ness: 0, upload_valid: 0
    RX antenna: 0x00000000
    EVM: 0x00000000; 0x00000000; 0x00000000; 0x00000000
    RX done: 1, RX frame ok: 0, CRC error: 0
    Decrypt CRC err: 0, PHY err: 0, MIC err: 0
    Pre delim CRC err: 0, uAPSD Trig: 0
    RXKeyIdxValid: 0, KeyIdx: 0, PHY error: 0
    RX more Aggr: 0, RX aggr 0, post delim CRC err: 0
    hw upload data type: 0; position bit: 0
    Hi RX chain: 0, RxFirstAggr: 0, DecryptBusy: 0, KeyMiss: 0
[1467602208.961332] [100142] RXSTATUS
    RSSI 15/19/20 / 128/128/128; combined: 23; rate=0x09
    Len: 390; more=0, delim=0, upload=1
    RX timestamp: 1427944558
    GI: 0, 2040: 0, parallel40: 0, stbc=0
    Not sounding: 1, ness: 0, upload_valid: 1
    RX antenna: 0x00000000
    EVM: 0x00000000; 0x00000000; 0x00000000; 0x80808080
    RX done: 1, RX frame ok: 1, CRC error: 0
    Decrypt CRC err: 0, PHY err: 0, MIC err: 0
    Pre delim CRC err: 0, uAPSD Trig: 0
    RXKeyIdxValid: 0, KeyIdx: 0, PHY error: 0
    RX more Aggr: 0, RX aggr 0, post delim CRC err: 0
    hw upload data type: 1; position bit: 1
    Hi RX chain: 0, RxFirstAggr: 0, DecryptBusy: 0, KeyMiss: 0
[1467602208.961471] [100500] TXSTATUS TxTimestamp=1427940337, DescId=0x05a5, QCU=1
    DescId=0x05a50000
    DescLen=9, TxQcuNum=1, CtrlStat=0, DescId=0x168c
    TxTimestamp: 1427940337
    TxDone=1, SeqNo=768, TxOpExceed=0, TXBFStatus=0
    TXBfMismatch=0, BFStreamMiss=0, FinalTxIdx=0
    TxBfDestMiss=0, TxBfExpired=0, PwrMgmt=0, Tid=0, FastTsBit=1
    Frmok=1, xretries=0, fifounderrun=0, filt=0
    DelimUnderrun=0, DataUnderun=0, DescCfgErr=0, TxTimerExceeded=0
    RTScnt=0, FailCnt=0, VRetryCnt=0
    RX RSSI 0 [15 19 20]
    RX RSSI 1 [128 128 128] Comb=23
    BA Valid=0
    BALow=0xffffffff
    BAHigh=0xffffffff

TODO