When I was using Keil.TM4C_DFP.1.1.0.pack, I found that the TM4C123GH6PM.h header file of cmsis of tiva has a problem. The first 256 positions of the GPIODATA register should not be defined as '__I' in the structure GPIOA Structure. The P660 in the Tiva data sheet is RW, please confirm this issue.
Here is my proof！
P660 and P662、P54
So this is clearly problematic in the CMSIS file definition.
Thanks for your patience.
Unfortunately, the corresponding Pack is no more maintained, as confirmed by TI.