[SOLVED] Radeon RX Vega 56 freezes when connected through A/V receiver before login

Mar 27, 2017
ASRock Fatal1ty Z270 Gaming K6
Intel Core i7-7700K Kaby Lake Quad-Core 4.2 GHz
NVidia GeForce GTX 1070
iMac, MacBook Pro
Let me first state that my system works flawlessly when connected directly to a TV through either HDMI or DVI input.
My problem is when I try to connect the GPU through HDMI input of a Sony A/V DA2800ES. The receiver passes through the video to the TV over HDMI.

When I boot everything shows, I get the BIOS, then Clover boot menu, starting of Mac OS and up to the login screen, when all of a sudden the monitor (TV) blinks like it refreshes and freezes the whole system. The system freezes after that secondary refresh which comes anywhere between 2/3 seconds after the login screen appears. I feel like if I'm quick enough, I can even login.

My system's dual-boot, and Windows loads and works fine without issues, so I definitely suspect the AMD driver and/or framebuffer settings.

Has anybody come up with a problem and possible solution for this.For now, I switch the source form the TV when I use Mac or other sources like PS, Blu-ray, etc, but my sound from the Mac goes out from the TV speakers, and not the A/V receiver.

Here's my system

Motherboard: Asrock Z390 Phantom Gaming 7, iGPU is disabled in the BIOS
CPU: Intel Core i7-9700K 3.6 GHz 8-Core Processor
GPU: Asrock Phantom Gaming X Radeon RX VEGA 56 8G
SSD: M2 Samsung SSD 970 EVO 1TB
Clover bootloader
MacOS: Catalina 10.15.4 (19E287)

I had a clean installation, no upgrade, and it was relatively straight forward. Everything worked from the install- GPU, audio, NIC. I am yet to install M.2 NGFF bluetooth and WiFi

The crash report backtrace suggested that the problem is in AMD driver's handling HDCP authentication under MacOS.

Eliminate HDCP. I don't know how to do this in the driver or if that's even possible, but there is a good hardware solution- enter HDMI splitter. Not just any splitter, but one that doesn't conform, or doesn't implement HDCP. You need to read through specifications and find out. They don't say "We are not implementing HDCP"

This cheep HDMI splitter does the job very well -

I'd appreciate if somebody finds and posts a driver's solution. I like to have options, though my solution works very well, I don't see drop in the video or audio quality.
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