The logging system inside TFM is not unified due to:

Using toolchain 'printf' a long time ago.
'printf' maybe expensive.
Please design a new logging system, to cover:

Split core logging and Secure Partition logging.
Both logs can be enabled/disabled by MACROs.
Core logging needs to simple, do not support formatting.
Core logging using TLV format.
Secure Partition logging supports formatting.
Two logging systems have different HAL underlayers.
The actions:

Create design docs and call for review.
After reviewed, provide patches.
Implement patches on various platforms.

DoD:

Both design doc and patches need to be public.