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This version (05 Mar 2021 12:36) was approved by Laszlo Nagy.The Previously approved version (14 Jan 2021 05:38) is available.Diff

Running one of the below commands on a Linux based system will return the status of the JESD link. This is one of the firsts steps to diagnose the link.

#jesd_status
or
#grep "" /sys/bus/platform/devices/*.axi-jesd*/status*
   Link is enabled
   Measured Link Clock: 184.320 MHz
   Reported Link Clock: 184.320 MHz
   Lane rate: 7372.800 MHz
   Lane rate / 40: 184.320 MHz
   LMFC rate: 11.520 MHz
   SYNC~: deasserted
   Link status: DATA
   SYSREF captured: Yes
   SYSREF alignment error: No

Common symptoms

Below table describes the most commonly occurred problems during link bring-up and solutions to overcome these in a Linux environment.

Cause: Base address mismatch between HDL and device tree, adi,axi-jesd204-tx-1.0 or adi,axi-adxcvr-1.0 driver does not probes.

Identify: Check address allocation in the block design or system_bd.tcl against the corresponding device tree physical and link layer nodes.

Fix: Adjust addresses. For ZCU102 add 0x20000000 offset to the address used in HDL.


Cause: QPLL or CLL does not lock due missing reference clock.

Identify: Check reference clock location constraints. Check if ref clock reaches the in use quads.

Fix: Adjust location constraints.

Cause: QPLL or CLL does not lock due incorrect synthesis parameters.

Identify: Check channel and common util_adxcvr parameters against ones created with the transceiver wizard.

Fix: Adjust synthesis parameters of the util_adxcvr component.

Cause: QPLL or CLL does not lock due frequency mismatch of reference clock. Reference clock frequency is not the one the CPLL or QPLL was set to handle forcing the VCO go out of range.

Identify: Check reference clock generation settings.

Fix: Adjust setting of the clock chip to generate the correct frequency.


Cause: QPLL can't find a configuration for desired lane rate with the given reference clock.

Identify: Check boot log. Check the required lane rate ref clock combination against the constraints defined in the transceiver manual.

Fix: Configure the clock chip for different reference clock or switch to CPLL.


Cause: SYNC~ signal does not reach link layer hdl component

Identify: Check location constraints against schematic

Fix: Adjust location constraints to match the schematic

Cause: SYNC~ signal polarity reversed

Identify: Check constraints and schematic, look for any polarity inversion

Fix: Adjust location constraints to match the schematic

Cause: JESD Rx can’t detect the CGS characters due different lane rate settings

Identify:

  • Check if “Measured Link Clock” matches “Reported Link Clock” and “Lane Rate / 40”
  • Check is lane rate is as expected
  • If OUTDIV_CLK is used for link clock adjust out-clk-select to match Lane Rate/ 40
  • If dedicated link clock is used adjust the external clock chip from device tree to output a clock of Lane Rate / 40

Fix: Some general rules that always should hold:

  • LaneRate = SampleRate * (10/8) * (M/L) * NP
  • SampleRate = DACrate / TotalInterpolation
  • LinkClock = LaneRate/40
  • If OUTDIV_CLK is used: LinkClock = RefClock/(OutClkSel==4 ? 2 : OutClkSel==3 ? 1 : 1)

Where:

  • M - adi,converters-per-device, device tree property from axi-jesd204-tx node
  • L - number of lanes per link, parameter of JESD IP
  • NP - adi,bits-per-sample device tree property from axi-jesd204-tx node
  • RefClock – reference clock for the transceivers
  • SampleRate - rate of sample that feeds the JESD link
  • DACrate – DAC raw sample rate after interpolation,
  • TotalInterpolation – product of selected interpolations on the datapath e.g dacInterpolation *channelInterpolation
  • OutClkSel - adi,out-clk-select device tree property from xcvr node

Cause: Missing SYSREF at peripheral

Identify: #jesd_status or #grep “” /sys/bus/platform/devices/*.axi-jesd*/status*

Link status: CGS
SYSREF captured         No 

Fix: Make sure SYSREF is connected to the Link Transmit peripheral and is property driven.


Cause: Lane polarity inversion

Identify: Read received ILAS registers from DAC, in such case they do not make any sense compared to the LANEn_ILAS0..3 registers of the axi_jesd204_tx. ILAS checksum mismatch.

Fix: For each in use lane adjust the corresponding bit in the TX_LANE_INVERT parameter of the util_adxcvr component to match any polarity inversion from the schematic


E.g.: For a Link Clock: 184.320 MHz; Nothing is transmitted from the transport layer but spectrum looks like below:

Cause: Mismatch in scrambling configuration.

Identify: Check scrambling configuration registers from DAC against LINK_CONF1 config register SCRAMBLER_DISABLE bit of the link transmit peripheral.

Fix: Adjust the above bits to match configuration.


Cause: Swapped lanes, source ‘Lane n’ connects to other than sink ‘Lane n’;

Identify: Read received LID in the ILAS registers of the DAC, in such case they are out of order, permuted

Fix: Adjust link layer to physical layer connections in the FPGA block design through ad_xcvrcon procedure lane_map parameter; or \\Adjust crossbar from the DAC through the device tree nodes


Cause: Incorrect or missing constraint of the device clock (lane rate / 40)

Identify: Report clocks of the transport layer, link layer component

Fix: In the constraints file define/create clocks with period that match desired lane rate / 40


SYSREF alignment error: Yes

Cause: frequency of SYSREF signal is not as expected

Identify: Check SYSREF generator parameters.

Fix: Set the frequency of SYSREF to be integer multiple of the reported local multiframe clock (LMFC)

Cause: SYSREF signal sampling does not meet setup/hold requirements.

Identify: Check if SYSREF path is constrained.

Fix: Define timing constraints for SYSREF in edge aligned source synchronous interface mode and adjust device clock and SYSREF phase from the clock chip accordingly.


Template

Cause: template

Identify: template

Fix: template


More Information

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resources/fpga/peripherals/jesd204/jesd204_troubleshooting.txt · Last modified: 05 Mar 2021 12:35 by Laszlo Nagy