Shouldn't your while statement have its own { } brackets?
It looks like the code is waiting for serial input in that while so the trailing semicolon is the only code required to be executed until serial input becomes available.
It might make the program easier to understand if it was written using an if instead of a while and would be non blocking if/when that matters in a larger program.
void loop(void)
{
if (Serial.available())
{
dataRx = Serial.read();
tft.setTextColor(YELLOW);
tft.setTextSize(2);
tft.print(dataRx);
}