ISR functions do not get inlined as they are designed to get generated as a separate function. This is done to separate the driver related code and algorithm code.
To control inlining of function in generated code, please refer to the following documentation: https://www.mathworks.com/help/coder/ug/control-inlining-using-configuration-object.html.
To control inlining of subsystem code in Simulink, please refer to the following documentation: https://www.mathworks.com/help/ecoder/ug/inline-subsystem-code-ecoder.html
