Collabobo presented , DRM-drive (Direct Rendering Manager) Pancsf , working at the level of the Linux nucleus. Changes for the use of a new driver in MESA are planned to be published in the near future. The driver is aimed at using GPU MALI (G710+), which uses the technology CSF (sommand Stream FrontenD), which takes to the side of the firmware some functions of the driver to reduce the load on the CPU and offers a new model for organizing work on GPU.
In the new generation of the GPU Mali, the Job Manager planner is replaced by the CSF interface (Command Stream FrontenD), in which instead of the model based on the work chain, a model based on the flux of commands with the planning of the line flow on the firmware stream is used. A separate Cortex-M7 microcontroller is built into the planner’s work in the GPU, and a special command unit unit is provided to execute the CSF instructions. Such features require a fundamentally different organization of transmission of work in GPU from the user space.
Initially, an attempt was made to implement the support of the GPU MALI based on the CSF in the Panfrost driver, but the developers came to the conclusion that this will lead to a great complication of the existing driver and for CSF the creation of a new driver built using other architecture. The Pancsf New Driver, proposed for testing, has a completely new UAPI, new work planning logic and a new MMU/GPU-VA management logic. As the basis for the new driver, the existing Panfrost code was used. The Pancsf driver borrowed typical driver initialization templates, frequency management and power management, which will probably be processed, since some energy consumption controls in the new GPU Mali are put into firmware.