Arm Mali "Valhall" Reverse-Engineering Started

The Panfrost open-source Linux graphics driver stack has matured nicely for Arm Mali Midgard and Bifrost generations but for the past two years now there has been Valhall as the latest-generation Arm Mali microarchitecture. There is now work underway on reverse-engineering Valhall for ultimately wiring up with open-source graphics driver support.

Panfrost lead developer Alyssa Rosenzweig commented today that reverse-engineering work has begun for Valhall with a focus on the Mali G78 in particular. This reverse engineering has been going on for just about one month but there is already some instruction set documentation made as well as an XML-based representation.

An assembler and disassembler for the Valhall instruction set has also been made to help in the reverse-engineering effort to get the latest Mali GPUs working with an open-source driver.

This reverse engineering has been hampered by the lack of Linux-friendly devices with Valhall graphics and thus having to use an Android smartphone (Samsung Galaxy S21) for the reverse engineering to date.

More reverse engineering is still ahead but at least enough information learned so far to begin work on Valhall compiler support. Ultimately the existing Bifrost support within the Mesa OpenGL/Vulkan drivers will ultimately be adapted to work with Mali Valhall but will still take some time as well as for Linux-friendly (non-Android) devices to come to market with these newer graphics.

More details on the reverse-engineering effort via this blog post.