Fun with CSF firmware (RK3588 GPU firmware)

a day ago

The Mali v10 GPUs require firmware (mali_csffw.bin) to be present in firmware directories like /lib/firmware for the GPU to function.
The firmware runs on a Cortex-M7 microcontroller within the GPU, handling tasks previously managed by the kernel.
The MCU operates at up to 990 MHz on RK3588 and controls its own page tables to access memory.
Memory access involves three layers: MCU's MPU, MCU memory mappings, and GPU MMU, each with distinct permissions and controls.
Interrupts facilitate communication between the kernel, MCU, userspace, and GPU components for tasks like initialization and power management.
MMIO regions at 0x04000000 and 0x40000000 are critical for shared buffers and hardware control, respectively.
The firmware image (mali_csffw.bin) includes memory mappings and tracebuffer configurations, with some sections marked as GPL-2.
Attempts to use Rust for firmware development faced tooling challenges, leading to a hybrid approach with C.
GDB integration was achieved for debugging the MCU, requiring a patched kernel for access via debugfs.
MicroPython was ported to the MCU, offering a scripting environment for firmware development and user interaction.

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