SPI Boot in RZ/T1

loader_init2() →　bus_init() after cpg_init() → spibsc_init() after bsc_init() → 

https://www.renesas.com/en-us/doc/products/mpumcu/apn/rz/r01an3010ej0120-rzt1-spibsc.pdf

SPI Flash is already mapped at reset boot up by the boot function and the default setting for SPI Flash is extended address mapped.

3.5.1 Boot Function
After reset is released on this LSI, the boot function executes the boot processing described below. The boot processing can extract a loader program that was stored in an external memory in advance by a user, to the internal tightly coupled
memory (TCM) area, and hand over the processing to the loader program at the start address of that program.
(1) Setting the bus controller (SPIBSC or BSC) specified by the mode setting pins (MD2, MD1, and MD0)
(2) Loading parameters for the loader from an external memory, and executing checksum
(3) Setting for speeding up the peripheral module (SPIBSC or BSC) by using parameters for the loader
(4) Loading the loader program from an external memory
(5) Branching off to the start address of the loader program extracted to the tightly coupled memory (TCM)
Parameters for the loader can have configuration information that suite for the user system, such as, loader program information, cache setting for speeding up the boot processing, and bus controller (SPIBSC or BSC) settings. Parameters
for the loader must be stored in an external memory in advance by a user.

https://www.iar.com/support/tech-notes/general/execute-in-ram-after-copying-from-flashrom-v5.20-and-later/