[Bug 1922754] Re: Make AMD gpus choose YCbCr420 encoding automatically when required for 4k 60Hz output

** Description changed:

On some setups, while the monitor and the gpu support display modes with
pixel clocks of up to 600MHz, the link encoder might not. This prevents
YCbCr444 and RGB encoding for 4k60Hz, but YCbCr420 encoding might still be
possible. However, which color mode is used is decided before the link
encoder capabilities are checked. This patch fixes the problem by retrying
to find a display mode with YCbCr420 enforced and using it, if it is
valid.

Patch already got accepted upstream for linux-next:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-
next.git/commit/?id=14e4a095b29fd290a9b80f6e553adcfcf01672d1 and applies
without modifications to ubuntu-focal/hwe-5.8
+
+ Commit-hash: 14e4a095b29fd290a9b80f6e553adcfcf01672d1

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https://bugs.launchpad.net/bugs/1922754

Title:
Make AMD gpus choose YCbCr420 encoding automatically when required for
4k 60Hz output

Status in linux package in Ubuntu:
New

Bug description:
On some setups, while the monitor and the gpu support display modes with
pixel clocks of up to 600MHz, the link encoder might not. This prevents
YCbCr444 and RGB encoding for 4k60Hz, but YCbCr420 encoding might still be
possible. However, which color mode is used is decided before the link
encoder capabilities are checked. This patch fixes the problem by retrying
to find a display mode with YCbCr420 enforced and using it, if it is
valid.

Patch already got accepted upstream for linux-next:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-
next.git/commit/?id=14e4a095b29fd290a9b80f6e553adcfcf01672d1 and
applies without modifications to ubuntu-focal/hwe-5.8

Commit-hash: 14e4a095b29fd290a9b80f6e553adcfcf01672d1

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