James Hartle, Gravity: An Introduction to Einstein's General Relativity, p. 113: "If we accept the equivalence principle, we must also accept that light falls in a gravitational field with the same acceleration as material bodies." https://www.amazon.com/Gravity-Introduction-Einsteins-General-Relativity/dp/0805386629

Paul A. Tipler, Ralph A. Llewellyn, Modern Physics: "But according to the equivalence principle, there is no way to distinguish between an accelerating compartment and one with uniform velocity in a uniform gravitational field. We conclude, therefore, that A BEAM OF LIGHT WILL ACCELERATE IN A GRAVITATIONAL FIELD AS DO OBJECTS WITH REST MASS. For example, near the surface of Earth light will fall with acceleration 9.8 m/s^2." http://web.pdx.edu/~pmoeck/books/Tipler_Llewellyn.pdf

The problem with this obvious fact is that it leaves no place for Einstein's gravitational time dilation. The speed of falling light increases as per Newton, the frequency increases proportionally (proved by the Pound-Rebka experiment), and...no gravitational time dilation, goodbye Einstein.

Einstein found it extremely profitable to introduce gravitational time dilation but realized that it is only consistent with DECREASING speed of falling light. So general relativity predicts that, as light falls towards a source of gravity, its speed DECREASES (and increases as the light moves in the opposite direction).

But such a flagrant violation of the equivalence principle is dangerous for the Einstein Cult so Einsteinians never discuss the preposterous prediction of general relativity. Rather, as the above quotations show, they teach the Newtonian prediction, as an obvious consequence of the equivalence principle. Still I have found a few explicit references to the general relativity's preposterous prediction:

"Contrary to intuition, the speed of light (properly defined) decreases as the black hole is approached...If the photon, the 'particle' of light, is thought of as behaving like a massive object, it would indeed be accelerated to higher speeds as it falls toward a black hole. However, the photon has no mass and so behaves in a manner that is not intuitively obvious." http://www.physlink.com/Education/AskExperts/ae13.cfm

"Simply put: Light appears to travel slower near bigger mass (in stronger gravitational fields)." https://speed-of-light.com/speed_of_light_gravity.html

"Thus, as φ becomes increasingly negative (i.e., as the magnitude of the potential increases), the radial "speed of light" c_r defined in terms of the Schwarzschild parameters t and r is reduced to less than the nominal value of c." https://www.mathpages.com/rr/s6-01/6-01.htm

The first two quoted phrases from the video below imply that the speed of falling light INCREASES; the last two quoted phrases imply that the speed of falling light DECREASES:

"All objects, regardless of composition or mass, fall with the same gravitational acceleration g...The light is perceived to be falling in a gravitational field just like a mechanical object would...The change in speed of light with change in height is dc/dh=g/c...The speed of light INCREASES for every meter you go above the earth by..."

*View: https://www.youtube.com/watch?v=FJ2SVPahBzg*