3840x2160 fails with 30Hz with HDMI

[stag019]

The radeon graphics card driver assumes any pixel clock speed over 165000 should be using Dual-Link DVI, although the speeds are possible over HDMI as of HDMI 1.3.

The fix, as well as a link to a more detailed bug report, can be found here:
https://github.com/torvalds/linux/commit/d03874c881a049a50e12f285077ab1f9fc2686e1

[Andy Whitcroft (apw)]

I have built some test kernels with that patch applied, can you test these kernels and confirm they resolve the issue. Kernels are at the URL below:

    http://people.canonical.com/~apw/lp1295032-trusty/

Please report any testing here.

[stag019 (stag019)]

Unfortunately, this didn't fix it for me.
`cat /proc/version_signature` return "Ubuntu 3.13.0-18.38lp1295032v201403200948-generic 3.13.6" so the kernel should have installed correctly.
The mode doesn't show up in the System Settings - Displays. I then tried running `cvt 3840 2160 30` and adding that with xrandr, but that caused my monitor to show "Not Supported" (just as it had before).
I can confirm my monitor/graphics card can support the mode using AMD's proprietary drivers.
Any suggestions?

[madbiologist (me-again)]

This patch is included in the upstream 3.13.7 kernel. Ubuntu 14.04 "Trusty Tahr" is now based on the 3.13.7 kernel. Can you update and retest?

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]