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add debug section

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Jiao Xianjun 2019-12-13 09:51:51 +01:00 committed by GitHub
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@ -7,6 +7,7 @@ Above figure shows software and hardware/FPGA modules that compose the openwifi
- [sdrctl command](#sdrctl-command)
- [rx packet flow and filtering config](#rx-packet-flow-and-filtering-config)
- [tx packet flow and config](#tx-packet-flow-and-config)
- [debug methods](#debug-methods)
## driver and software overall principle
@ -180,3 +181,52 @@ Each time when FPGA send a packet, an interrupt will be raised to Linux reportin
- packet length and sequence number
- packet sending result: packet is sent successfully (FPGA receive ACK for this packet) or not. How many retransmissions are used for the packet sending (in case FPGA doesn't receive ACK for several times)
- send above information to upper layer (Linux mac80211 subsystem) via ieee80211_tx_status_irqsafe()
## debug methods
### dmesg
To debug/see the basic driver behaviour, you could use dmesg command in Linux. openwifi driver prints normal tx/rx packet information when a packet is sent or received. The driver also prints WARNING information if it feels something abnormal happens. You can search "printk" in sdr.c to see all the printing points.
- tx printing example
sdr,sdr openwifi_tx: 116bytes 48M FC0208 DI002c addr1/2/3:b827ebe65f1e/66554433224c/66554433224c SC1df0 flag40000012 retry2 ack1 q0 sn1075 R/CTS 00 1M 0us wr/rd 19/19
- printing from sdr driver, openwifi_tx function.
- 116bytes: packet size (length field in SIGNAL) is 116 bytes.
- 48M: MCS (rate field in SIGNAL) is 48Mbps.
- FC0208: Frame Control field 0x0208, which means type data, subtype data, to DS 0, from DS 1 (a packet from AP to client).
- DI002c: Duration/ID field 0x002c. How many us this packet will occupy the channel (including waiting for ACK).
- addr1/2/3: address fields. Target MAC address b827ebe65f1e, source MAC address 66554433224c (openwifi).
- SC1df0: Sequence Control field 0x1df0, which means that the driver inserts sequence number 0x1df0 to the packet under request of upper layer.
- flag40000012: flags field from upper layer struct ieee80211_tx_info (first fragment? need ACK? need sequence number insertion? etc.). Here is 0x40000012.
- retry2: upper layer tells us the maximum number of retransmissions for this packet is 2.
- ack1: upper layer tells us this packet needs ACK.
- q0: the packet goes to FPGA queue 0.
- sn1075: PHY/FPGA sequence number 1075. This is different from Sequence Control asked by upper layer. This is for cross check between FPGA/interrupt and driver.
- R/CTS 00: upper layer believes this packet doesn't need RTS/CTS mechanism (Because the packet size is below the RTS threshold).
- 1M 0us: if RTS/CTS is asked to be used by upper layer, it should use xM rate and Xus duration.
- wr/rd 19/19: the write/read index of buffer (shared buffer between the active openwifi_tx and background openwifi_tx_interrupt).
- rx printing example
sdr,sdr openwifi_rx_interrupt: 120bytes ht0 54M FC0108 DI002c addr1/2/3:66554433224c/b827ebe65f1e/66554433224c SCcf20 fcs1 sn117 i117 -36dBm
- printing from sdr driver, openwifi_rx_interrupt function.
- 120bytes: packet size (length field in SIGNAL) is 120 bytes.
- ht0: this is non-ht packet.
- 54M: MCS (rate field in SIGNAL) is 54Mbps.
- FC0108: Frame Control field 0x0208, which means type data, subtype data, to DS 1, from DS 0 (a packet client to openwifi AP).
- DI002c: Duration/ID field 0x002c. How many us this packet will occupy the channel (including waiting for ACK).
- addr1/2/3: address fields. Target MAC address 66554433224c (openwifi), source MAC address b827ebe65f1e.
- SCcf20: Sequence Control field 0x1df0, which means that the packet includes sequence number 0xcf20 (under request of upper layer of the peer).
- fcs1: FCS/CRC is OK.
- sn117: HY/FPGA sequence number 117. This is different from Sequence Control asked by upper layer. This is for cross check between FPGA/interrupt and driver.
- i117: current rx packet DMA buffer index 117.
- -36dBm: signal strength of this received packet.
### native Linux tools
For protocol, many native Linux tools you still could rely on. Such as tcpdump.
### FPGA
For FPGA itself, FPGA developer could use Xilinx ILA tools to spy on FPGA signals.