How to debug Core A53 of iMX8MP using JLink debugger

[AbdulELPRO]

Hi, I'm trying to debug imx8mp (Custom board, SOM Solidrun) using J-Link but once I tried to connect Linux rebooted every time even I tried from UBoot as well. see the logs below from J-LINK

SEGGER J-Link Commander V8.54 (Compiled Jul 23 2025 12:21:02)
DLL version V8.54, compiled Jul 23 2025 12:20:05

Connecting to J-Link via USB...O.K.
Firmware: J-Link V10 compiled Jan 30 2023 11:28:07
Hardware version: V10.10
J-Link uptime (since boot): N/A (Not supported by this model)
S/N: 600113317
License(s): RDI, FlashBP, FlashDL, JFlash, GDB
VTref=3.425V

Type "connect" to establish a target connection, '?' for help
J-Link>connect
Please specify device / core. <Default>: MIMX8ML8_A53_0
Type '?' for selection dialog
Device>
Please specify target interface:
J) JTAG (Default)
S) SWD
T) cJTAG
TIF>J
Device position in JTAG chain (IRPre,DRPre) <Default>: -1,-1 => Auto-detect
JTAGConf>
Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>
Device "MIMX8ML8_A53_0" selected.

Connecting to target via JTAG
ConfigTargetSettings() start
ConfigTargetSettings() end - Took 30us
InitTarget() start
InitTarget() end - Took 52.3ms
TotalIRLen = 5, IRPrint = 0x01
JTAG chain detection found 1 devices:
#0 Id: 0x00000000, IRLen: 05, Unknown device
Connect failed. Resetting via Reset pin and trying again.
ConfigTargetSettings() start
ConfigTargetSettings() end - Took 40us
InitTarget() start
DAP: Could not power-up system power domain.
InitTarget() end - Took 4.70ms
Could not measure total IR len. TDO is constant high.
Failed to identify target. Resetting via Reset pin and trying again.
ConfigTargetSettings() start
ConfigTargetSettings() end - Took 14us
InitTarget() start
DAP: Could not power-up system power domain.
InitTarget() end - Took 3.80ms

****** Error: CPU-TAP not found in JTAG chain
Supply voltage too low (1 Volt is required, Measured: 0.0 Volt).
Please check target power.
Target voltage too low. Please check https://kb.segger.com/J-Link_cannot_connect_to_the_CPU#Target_connection.
Error occurred: Could not connect to the target device.
For troubleshooting steps visit: https://kb.segger.com/J-Link_Troubleshooting
J-Link>

[AbdulELPRO · Accepted solution]

Got working, its need to be in eMMC mode 

openocd -f interface/jlink.cfg -f board/imx8mp-evk.cfg
Open On-Chip Debugger 0.12.0 (2025-07-10) [https://github.com/sysprogs/openocd]
Licensed under GNU GPL v2
libusb1 d52e355daa09f17ce64819122cb067b8a2ee0d4b
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
Info : [imx8mp.a53.0] Hardware thread awareness created
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : J-Link V10 compiled Jan 30 2023 11:28:07
Info : Hardware version: 10.10
Info : VTarget = 3.425 V
Info : clock speed 4000 kHz
Info : JTAG tap: imx8mp.cpu tap/device found: 0x5ba00477 (mfg: 0x23b (ARM Ltd), part: 0xba00, ver: 0x5)
Info : imx8mp.a53.0: hardware has 6 breakpoints, 4 watchpoints
Info : [imx8mp.a53.0] external reset detected
Info : [imx8mp.a53.0] Examination succeed
Info : [imx8mp.ahb] Examination succeed
Info : [imx8mp.a53.0] starting gdb server on 3333
Info : Listening on port 3333 for gdb connections
Info : [imx8mp.m4] starting gdb server on 3334
Info : Listening on port 3334 for gdb connections
Info : [imx8mp.ahb] gdb port disabled

[Rita_Wang]

Good news it can works and thanks for sharing.

[AbdulELPRO]

When I tried openocd then I got the following: 

openocd -f interface/jlink.cfg -f board/imx8mp-evk.cfg
Open On-Chip Debugger 0.12.0 (2025-07-10) [https://github.com/sysprogs/openocd]
Licensed under GNU GPL v2
libusb1 d52e355daa09f17ce64819122cb067b8a2ee0d4b
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
Info : [imx8mp.a53.0] Hardware thread awareness created
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : J-Link V10 compiled Jan 30 2023 11:28:07
Info : Hardware version: 10.10
Info : VTarget = 3.425 V
Info : clock speed 400 kHz
Info : JTAG tap: imx8mp.cpu tap/device found: 0x088e601d (mfg: 0x00e (Freescale (Motorola)), part: 0x88e6, ver: 0x0)
Warn : JTAG tap: imx8mp.cpu UNEXPECTED: 0x088e601d (mfg: 0x00e (Freescale (Motorola)), part: 0x88e6, ver: 0x0)
Error: JTAG tap: imx8mp.cpu expected 1 of 1: 0x5ba00477 (mfg: 0x23b (ARM Ltd), part: 0xba00, ver: 0x5)
Error: Trying to use configured scan chain anyway...
Error: IR capture error at bit 4, saw 0x21 not 0x...3
Warn : Bypassing JTAG setup events due to errors
Error: Invalid ACK (0) in DAP response