What is the efficient way to measure the time taken by ADC DMA conversion?

[BSale.1]

I toggle a GPIO pin in the ADC call back function, I get time values on the oscilloscope close what is the supposed to be according to the datasheet, is that correct and efficient? Is there a method better maybe?

[TDK]

Set up continuous conversions, monitor the pin on an oscilloscope directly at the pin or as close as practical and you should be able to see the effect when the sampling capacitor is connected or disconnected. Measure the distance between events on the scope.

[BSale.1]

That is what I did, I got values close to 3 to 3.2uS which is close to the calculate value from the datasheet which is 2.9uS.