25.02.2021 09:27, Nicolin Chen пишет:
...
>> The partially revert should be okay, but it's not clear to me what makes
>> difference for T124 since I don't see that problem on T30, which also
>> has active display at a boot time.
> 
> Hmm..do you see ->attach_dev() is called from host1x_client_iommu_attach
> or from of_dma_configure_id/arch_setup_dma_ops?
> 

I applied yours debug-patch, please see dmesg.txt attached to the email.
Seems probe-defer of the tegra-dc driver prevents the implicit
tegra_smmu_attach_dev, so it happens to work by accident.