The AMD Graphics Driver for Linux 6.4 Has Been Updated with Many Boosted Functionality for the Virtual Machine

On Friday, a pull request including early updates to the AMDGPU kernel graphics driver was submitted for DRM-Next. This constitutes part of the early feature work that has accumulated in preparation for the Linux 6.4 kernel cycle. The latest update to the AMDGPU kernel driver includes a number of bug patches that affect a variety of features and components, including the UMC RAS, DCN 3.2, FreeSync, SR-IOV, assorted IP blocks, USB4, and others. On the functionality side, there are a few power-related additions, which are just mentioned in passing in the change log… These upgrades focus mostly on Van Gogh APUs, which is significant for the Valve Steam Deck and will benefit its graphics in the future.

To begin, this kernel pull request presents a brand-new sysfs interface for the purpose of changing and setting thermal throttling. The thermal limit temperature can be read and updated in millidegrees Celsius using this, which has been set up specifically for Van Gogh. This “APU thermal cap” interface was just wired up for Van Gogh, and it appears to be Steam Deck driven feature work. This work is being done in order to improve SteamOS’s ability to manage the thermal handling of the APU graphics.

The latest update to the AMDGPU kernel driver includes a number of bug patches that affect a variety of features and components, including the UMC RAS, DCN 3.2, FreeSync, SR-IOV, assorted IP blocks, USB4, and others. The pull request just makes a passing reference to “supported APUs” in relation to these power improvements; but, upon more investigation, the code reveals that it presently only applies to being handled on Van Gogh. These power features will be made available via sysfs, and Steam OS will automatically wrap around them. Moreover, there may be some new UI settings knobs added for users who want greater control over the thermal and performance aspects of their Steam Deck.

There is both a repair and a workaround for the AMD VCN handling on earlier Steam Decks with out-of-date BIOS versions included in this pull. The remedy involves disabling indirect SRAM on Van Gogh APUs with “broken” BIOSes. The solution is included in this pull. This pull request now provides support for exporting buffers via DMA-BUF, as well as multi-VMA page migration fixes and other fixes. This is located on the AMDKFD compute driver side of things.