The GPI input on derserializers is sent in the reverse direction on a GMSL1 link and output on GPO at the serializer. This can be used for getting an interrupt from a touchscreen controller back to an SoC at the seializer. There are a couple of things to be aware of when doing this.
1. Sending GPI transitions involves sending a 320us data sequence. This means GPO transitions 320us after GPI, and that transitions on GPI should not be closer than 320us. Note that an interrupt pulse less than 320us wide, will be streched to 320us.
2. When this data sequence is sent, the reverse control channel cannot be used for data (such as setting registers). The SoC should disable control data when an interrupt is possible and the interrupt should be disabled when data is being sent.