GPU Interrupt Service Routines

Typically there is an interrupt service routine (ISR) for the GPU and another for the display hardware’s VSync event. On completion of the port it is necessary to check that the ISR for the GPU is scheduled on completion of every GPU operation scheduled by the firmware. It is also necessary to check the VSync event on the display hardware additionally schedules an independent Vsync specific ISR for every VSync event.

These checks are very important since the platform can seem functional without one or both of these ISRs functioning correctly. This can result in a lengthy debug investigation weeks or months later and cause seemingly unrelated issues.