i.MX93 M33 Core: LPTMR Example stops functioning after Linux Kernel Boot

[anandhu-s]

Hi NXP Experts,

I am working with a custom i.MX93 evb using SDK v25.06.00. I am running the lptmr_timer example on the Cortex-M33 core. (debugging and coding using j link)

The Issue: The M33 application functions perfectly when I stop at the U-Boot prompt. I can see the LPTMR interrupts firing as expected:

Low Power Timer Example
LPTMR interrupt No.1
LPTMR interrupt No.2
...

However, as soon as I boot the Linux Kernel (A55), the LPTMR interrupts stop firing on the M33 side. It appears the kernel is interfering with the timer’s resources or clock gate. (Kernel dts attached)

Environment:

• Kernel: 6.6

• Bootloader: U-Boot 2024.04

Relevant Device Tree Observations: My current DTS does not explicitly enable &lptimer1 or &lptimer2, but it does include the standard imx93.dtsi. I suspect the Linux Clock Framework is gating the LPTMR clock because it sees no active consumer in the A55 domain.

Questions:

1. Is there a specific Resource Domain Controller (RDC) configuration required to "shield" the LPTMR from the A55?

2. How should I modify the Linux DTS to ensure the kernel doesn't gate the clocks used by the M33?

3. Is clk_ignore_unused the recommended approach, or is there a cleaner way to reserve this peripheral for the M33?

Thanks in advance!

[pengyong_zhang · Accepted solution]

Hi @anandhu-s 

Please use the attachment patch file. I have tested on my imx93 evk board, The issue was resolved after applying the patch file.

B.R

[anandhu-s]

This fixed the issue,
Thanks for the support.
Regards

[pengyong_zhang]

Hi @anandhu-s 

You should use the rpmsg dts file in uboot environment. then type "run prepare_mcore".

Please share all your test commands and result files.

B.R

[anandhu-s]

Hi @pengyong_zhang ,

Changing the dts didn't help.

U-boot env variables:

printenv
arch=arm
auth_os=auth_cntr ${cntr_addr}
baudrate=115200
board=imx93_BOARD_NAME
board_name=VENDOR_NAME BOARD_NAME
board_rev=iMX93
boot_a_script=load ${devtype} ${devnum}:${distro_bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr}
boot_extlinux=sysboot ${devtype} ${devnum}:${distro_bootpart} any ${scriptaddr} ${prefix}${boot_syslinux_conf}
boot_fit=no
boot_net_usb_start=usb start
boot_os=booti ${loadaddr} - ${fdt_addr_r};
boot_prefixes=/ /boot/
boot_script_dhcp=boot.scr.uimg
boot_scripts=boot.scr.uimg boot.scr
boot_syslinux_conf=extlinux/extlinux.conf
boot_targets=mmc0 mmc1 usb0
bootcmd=run distro_bootcmd;run bsp_bootcmd
bootcmd_mfg=run mfgtool_args;if iminfo ${initrd_addr}; then if test ${tee} = yes; then bootm ${tee_addr} ${initrd_addr} ${fdt_addr}; else boo;
bootcmd_mmc0=devnum=0; run mmc_boot
bootcmd_mmc1=devnum=1; run mmc_boot
bootcmd_usb0=devnum=0; run usb_boot
bootdelay=2
bootm_size=0x10000000
bootscript=echo Running bootscript from mmc ...; source
bsp_bootcmd=echo Running BSP bootcmd ...; mmc dev ${mmcdev}; if mmc rescan; then if run loadbootscript; then run bootscript; else if test ${s;
cntr_addr=0x98000000
cntr_file=os_cntr_signed.bin
console=ttyLP0,115200 earlycon
cpu=armv8
distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done
emmc_dev=0
ethaddr=de:92:87:67:06:fd
ethprime=eth1
fastboot_dev=mmc1
fdt_addr=0x83000000
fdt_addr_r=0x83000000
fdt_high=0xffffffffffffffff
fdtcontroladdr=fdefc7d0
fdtfile=imx93-11x11-evk-rpmsg.dtb
image=Image
initrd_addr=0x83800000
initrd_high=0xffffffffffffffff
kboot=booti
kernel_addr_r=0x80400000
loadaddr=0x80400000
loadbootscript=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${script};
loadcntr=fatload mmc ${mmcdev}:${mmcpart} ${cntr_addr} ${cntr_file}
loadfdt=fatload mmc ${mmcdev}:${mmcpart} ${fdt_addr_r} ${fdtfile}
loadimage=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${image}
mfgtool_args=setenv bootargs console=${console},${baudrate} rdinit=/linuxrc clk_ignore_unused
mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
mmcargs=setenv bootargs ${jh_clk} ${mcore_clk} console=${console} root=${mmcroot}
mmcautodetect=yes
mmcboot=echo Booting from mmc ...; run mmcargs; if test ${sec_boot} = yes; then if run auth_os; then run boot_os; else echo ERR: failed to au;
mmcdev=1
mmcpart=1
mmcroot=/dev/mmcblk1p2 rootwait rw
netargs=setenv bootargs ${jh_clk} ${mcore_clk} console=${console} root=/dev/nfs ip=dhcp nfsroot=${serverip}:${nfsroot},v3,tcp
netboot=echo Booting from net ...; run netargs; if test ${ip_dyn} = yes; then setenv get_cmd dhcp; else setenv get_cmd tftp; fi; if test ${s;
prepare_mcore=setenv mcore_clk clk-imx93.mcore_booted;
scan_dev_for_boot=echo Scanning ${devtype} ${devnum}:${distro_bootpart}...; for prefix in ${boot_prefixes}; do run scan_dev_for_extlinux; run;
scan_dev_for_boot_part=part list ${devtype} ${devnum} -bootable devplist; env exists devplist || setenv devplist 1; for distro_bootpart in ${t
scan_dev_for_extlinux=if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${boot_syslinux_conf}; then echo Found ${prefix}${boot_sysli
scan_dev_for_scripts=for script in ${boot_scripts}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${script}; then echo Founde
scriptaddr=0x83500000
sd_dev=1
sec_boot=no
serial#=baad668f81cc4a6d
soc=imx9
soc_type=imx93
splashimage=0x90000000
usb_boot=usb start; if usb dev ${devnum}; then devtype=usb; run scan_dev_for_boot_part; fi
vendor=VENDOR_NAME

Environment size: 4639/16380 bytes
u-boot=>

meanwhile, any other timer/methods for timer interrupts.
Regards.

[pengyong_zhang]

Hi @anandhu-s 

Sorry to reply late, I'm currently debugging your issue and will get back to you as soon as possible.

B.R

[pengyong_zhang]

Hi @anandhu-s 

Did you type the run prepare_mcore command to enable the m core? Then type boot enter the Linux environment

B.R

[anandhu-s]

Hi @pengyong_zhang 

'run prepare_mcore' didn't help. The issue still persists.

if i run the m core then try to boot the linux;

It's showing:

[ 1.965522] Call trace:
[ 1.967958] rproc_handle_resources.constprop.0+0x64/0x18c
[ 1.973435] rproc_boot+0x37c/0x57c
[ 1.976909] rproc_add+0x144/0x17c
[ 1.980298] imx_rproc_probe+0x4d0/0x5f0
[ 1.984215] platform_probe+0x68/0xc8
[ 1.987873] really_probe+0x148/0x2b0
[ 1.991522] __driver_probe_device+0x78/0x12c
[ 1.995863] driver_probe_device+0x3c/0x15c
[ 2.000032] __device_attach_driver+0xb8/0x134
[ 2.004461] bus_for_each_drv+0x88/0xe8
[ 2.008292] __device_attach+0xa0/0x190
[ 2.012114] device_initial_probe+0x14/0x20
[ 2.016282] bus_probe_device+0xac/0xb0
[ 2.020113] deferred_probe_work_func+0x80/0xb8
[ 2.024628] process_one_work+0x138/0x248
[ 2.028632] worker_thread+0x320/0x438
[ 2.032368] kthread+0x110/0x114
[ 2.035583] ret_from_fork+0x10/0x20
[ 2.039157] Code: 6b020063 8b22c098 91001301 540007c4 (b862c880)
[ 2.045231] ---[ end trace 0000000000000000 ]---

same case if it's run prepare_mcore -> boot ->  and then try to run the m core,  the m code doesn't work.

Regards,
Anandhu

[anandhu-s]

Hi,
can i get an update on this one ?
thanks.