Hikey960 Serial output keeps repeating. It never stops

I built OPTEE-AOSP on Hikey960.

I followed build steps from the below document.

It builds fine and passes all xtests, but screen didn’t show up.
So, I updated cloned kernel repository to the latest commit.
This solved the screen issues and passed all xtests.

Now I’m trying to look at serial port output.
When I worked with previous build (that did not pass 1 xtest), serial port output was stable and worked fine.
However with current build, after booting all images and normal world, it repeatedly gives some output lines. It never stops. The output that keeps repeating is below.

Of course, my hikey960 board is not connected with camera, and will it be the reason for these repeating output?
Does any one get same output? or Does any one know what the problems are here?

Thanks.

++ Update:

I found some differences with previous build.
The latest build outputs errors on wlcore, wl18xx_driver as below logs.
And then it starts repeating the message I mentioned.

[    9.205922] wl18xx_driver wl18xx.0.auto: loading /vendor/firmware/ti-connectivity/wl18xx-conf.bin failed with error -13
[    9.225155] wl18xx_driver wl18xx.0.auto: Direct firmware load for ti-connectivity/wl18xx-conf.bin failed with error -2
D/TC:? 1 __wq_rpc:39 sleep thread 1 0x3f056148 -1
[    9.247482] hisi_ddr_devfreq ddr_devfreq: ddr bandwdith request: 0 / 28472
[    9.248209] healthd: No battery devices found
[    9.262393] healthd: battery none chg=
[    9.292830] read descriptors
[    9.297252] hisi_ddr_devfreq ddr_devfreq: set down threshold:400000000
D/TC:? 0 load_elf:827 Lookup user TA ELF dba51a17-0563-11e7-93b1-6fa7b0071a51 (REE)
[    9.311656] read strings
[    9.318769] wl18xx_driver wl18xx.0.auto: Falling back to user helper

[    9.614201] wlcore: wl18xx HW: 183x or 180x, PG 2.2 (ROM 0x11)
[    9.625012] wlcore: loaded
[    9.694411] logd: logdr: UID=1000 GID=1003 PID=2800 n tail=50 logMask=8 pid=2660 start=0ns timeout=0ns
[    9.704801] logd: logdr: UID=1000 GID=1003 PID=2800 n tail=50 logMask=1 pid=2660 start=0ns timeout=0ns
[    9.741894] logd: logdr: UID=1000 GID=1003 PID=2800 n tail=0 logMask=8 pid=2660 start=0ns timeout=0ns