For the display issue, I think you can compare the bootloader log on nano A when the NG happened and after reboot.
According to the dmesg, the “slow” you saw from previous case seems due to below log.
This is from the reboot one. You can see that kernel directly inherit the EDID from BL (bootloader). However, this does not happen in your slow case. In slow case, kernel seems does not receive any display info from BL. I guess this is more reasonable because no BMP logo there so display should not initiate in cboot.
1.138490] tegradc tegradc.0: DC initialized, skipping tegra_dc_program_mode.
[ 1.138538] tegradc tegradc.0: hdmi: tmds rate:148351K prod-setting:prod_c_hdmi_75m_150m
[ 1.139117] tegradc tegradc.0: hdmi: get RGB quant from REG programmed by BL.
[ 1.139130] tegradc tegradc.0: hdmi: get YCC quant from REG programmed by BL.
I am not sure if you can still see the “slow” behavior after once reboot. If you still can, please check if the cboot log has anything different.
Also, I feel the log your shared in first comment is different from the case you are sharing now. For example, your previous log has “edid invalid” in both kernel log (though not complete), but the dmesg you just shared didn’t have them.
Please make sure you really use the same environment to dump log. Or just remove “quiet” in extlinux.conf so that uart log will include full dmesg.
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