Linux Will Finally Stop Flickering With AMD Stoney Ridge On 4K Displays

[phoronix]

Phoronix: Linux Will Finally Stop Flickering With AMD Stoney Ridge On 4K Displays

For those still running the AMD "Stoney Ridge" mobile APUs from 2016 that were launched aside Bristol Ridge with Excavator-based CPU cores and GCN 1.2 graphics, the Linux kernel has a fix finally for flickering issues when driving a 4K display off the APU...

http://www.phoronix.com/scan.php?page=news_item&px=Linux-4K-Fix-AMD-Stoney-Ridge

[rene]

oh well, don't quite know what is wrong, so let's disable a major features, ... amazing fix, not

[Saverios]

+1 for the horrible pun!

[intelfx]

oh well, don't quite know what is wrong, so let's disable a major features, ... amazing fix, not

You are assuming that hardware is infallible. It's not.
Sometimes the hardware just doesn't get the feature right (more often than not with early generations and early adopters). The driver then has no other options other than to avoid that feature and act like it's not there.

[Mario Junior]

AMD has no drivers. 😬

[cjcox]

I was just talking to someone yesterday about how you geared up for the new "instruction" in the new Intel CPU and it seems to always release and then get disabled and not fixed sometimes for one or two generations. Sigh... CPUs and QC.... not best friends yet.

[horizonbrave]

wow, only 4 years....

[agd5f]

For a little background, this only affects Stoney boards with limited vram (carve out) where the display buffer ends up in system memory because there is not enough room in vram. The IOMMU adds extra latency on top of the additional latency required for the GPU page tables required for creating the linear map of the system memory pages in the GPU's address space. IOMMU + GFX was never plan of record for displays in system memory and windows never used the IOMMU at all. All Linux SKUs had a larger carve out by default to accommodate this limitation. Most stoney boards had a larger carve out so they never hit this case in the first place. Even if you did hit this case, things like the display timing and speed of memory could have affected it so you may not have actually had any flickering.

[pegasus]

My rx550 does that too on 4k screen but not on 1080p screen. I'll try disabling iommu to see if there's any difference.

[dwagner]

My rx550 does that too on 4k screen but not on 1080p screen. I'll try disabling iommu to see if there's any difference.

"disable iommu" is among the frequently rumored miracle cures for all kinds of amdgpu driver ailments, but don't bet your money on it.