Find the range of values of p for which the expression $\displaystyle x^2-2x+px+p-2$ is never negative for all real values of $\displaystyle x$

I know how to solve this question except that I am having doubts in the part that "the expression $\displaystyle x^2-2x+px+p-2$"is never negative for all real values of x

What does that tell about the discriminant? is X always positive or equals zero? what would $\displaystyle b^2-4ac$ be?