There are two types of failure with respect to PHY tuning. When Enable PHY Mode is checked, then these two failures can be encountered. Before starting this, learn about OSPI PHY Tuning and PHY Tuning Attack Vector.

The first being "PHY enabling failed!!! Continuing without PHY..." and second will be failure to compute the OTP (Optimal Tuning Point). The first one occurs, when the attack vector is flashed but not read correctly. So, this in turn points back to sections 5.3.1 and 5.3.2. The second one occurs when the PHY Tuning algorithm returns failure. To debug this, the following steps can be considered:

1. By default, in flash_nor_ospi,c file, OSPI_phyTuneDDR is called. If the protocol used is configured in STR, then the function OSPI_phyTuneSDR must be called.
2. To debug PHY tuning failure, TI recommends generating the PHY tuning graph. Please refer the FAQ here. Upon PHY failure, the graph can be used as a reference to see where the OTP point is marked.