Ok, turns out it only works on some Intel based laptops. But for them this is still an improvement so I vote for this patch to be keept, as it has no downsides for other devices.
e.g. The Clevo NS50MU Barebone with an i7-1165G7 only outputs 4k@30Hz without this patch, but 4k@60Hz with YCbCr420 with this patch. Accoring to the spec sheet of the CPU it should be possible to output 4k@60Hz without relying on YCbCr420, but for some reasons this fails. (Didn't check on Windows). The Clevo L140CU with an i5-10210U cannot output 4k@60Hz with Chroma subsampling. The spec sheet does not give clear indication whether the CPU supports HDMI 1.4 or 2.0, but it does support 4k@30Hz which should be roughly the same bandwith requirement as 4k@60Hz with chroma subsampling. So i don't know where exactly this fails yet. TL;DR: Works on Clevo NS50MU, does not work on Clevo L140CU, but also has no negative effect on it -> Patch is still an improvent. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1934489 Title: Make Intel GPUs choose YCbCr420 encoding automatically when required for 4k 60Hz output Status in linux package in Ubuntu: Incomplete Status in linux source package in Groovy: In Progress Status in linux source package in Hirsute: Fix Committed Bug description: SRU Justification: Impact: On some setups, while the monitor and the GPU support display modes with pixel clocks of up to 600MHz, the connector might not. This prevents RGB encoding for 4k60Hz, but YCbCr420 encoding might still be possible. However, which color mode is used is decided before the pixel clock capabilities are checked, causing the check to fail and discarding 4k60Hz from the list of possible display modes. Fix: This patch fixes the problem by retrying to find a display mode with YCbCr420 enforced and using it, if it is valid. It's very similar to a patch submitted to amdgpu which fixed the same problem. Testcase: I personally tested on a Clevo NV40MB, but generally: Find a PC with a current Intel iGPU, but only a HDMI 1.4 output. Connect a 4k@60Hz display supporting YCbCr420 encoding to the HDMI port. Without the patch the maximum that can be set via xrandr is 3840 × 2160 30Hz. With the Patch 3840 × 2160 60Hz can be selected which will use YCbCr420 automatically. Prerequisite (included in this email patchset as 1/4): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3c4442aa22878091f16c8d9592f5f5b6a94d1556 Patchset already got accepted upstream and reached the torvalds tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eacba74d4d561ea6487d944417526e1b025cbebd https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=84d95f77f4aea3f22a486cd04777afd4ab0f0ea5 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=388b863509f76f6a5ecedd7ffdaf184aa813241e and needs only a minor modifications to apply to ubuntu-focal/hwe-5.8 Commit-hashes: 3c4442aa22878091f16c8d9592f5f5b6a94d1556 eacba74d4d561ea6487d944417526e1b025cbebd 84d95f77f4aea3f22a486cd04777afd4ab0f0ea5 388b863509f76f6a5ecedd7ffdaf184aa813241e To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1934489/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
