Alex Deucher told me to open a new bug report, so here I go. Summary so far: Kernel 4.0.2: HDMI image and audio working. Kernel 4.0.3 and upward: No HDMI. Kernel 4.0.4 with commit d5c3b64b9618214a5443c57c64511ab5fa599cec reverted: HDMI image works, audio does not. Kernel 4.0.4 with attachment 178001 [details] from bug 98751: HDMI image works, audio does not. Kernel 4.0.4 with attachment 178001 [details] from bug 98751 and 0f55db36d49d45b80eff0c0a2a498766016f458b reverted: HDMI image and audio working. Monitor in use: Samsung UE40H5090
The issue is still present on kernel 4.0.7. Little precision, that may be useful to diagnose the problem: - If I boot with that HDMI-connected screen turned off and then I turn it on with my X session already fully started, it is not automatically detected (the screen says “no signal”), but this used to work on older versions of linux (can’t remember which one introduced this “regression”). Next, if I manually configure it with that command: xrandr --output DVI-0 --mode 1920x1080 --output DVI-1 --right-of DVI-0 --mode 1920x1080 --output HDMI-0 --right-of DVI-1 --mode 1920x1080 the image on the screen works, but not the sound. - However, if I boot while that screen is already turned on (or if I turn it on while still on the gdm login screen), it is automatically detected and both the image AND the sound BOTH work immediately.
Alex Deucher: Any news on this? Currently I'm experiencing GPU stalls under heavy load (gaming, so far tested with Left 4 Dead 2 and Distance, both games need around 15 minutes of gameplay before screen freezes) and while I would love to debug this I can't as I'm pinned on the patched kernel (4.0.4) so I can't even test if a newer kernel would fix the issue (which came with a mesa update).
@Alex: Sadly, its not working, not at all. It's horribly broken since at least Linux 4.0, 3.18 still works. I have a Radeon HD 7770. Just tested with Linux 4.3 RC7 and it's still broken. Finally, I've found this report! It has driven me crazy over the last months. Dozens of hours flowed into my HDMI experiments with different monitors, AV Receivers, cables and boot parameters. Please fix this mess as soon as possible! There was this regression/patch that aimed to fix it but failed with it: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2d1c18bba15daf89d75ce475ecd2068f483aa12f