Linux's Lima DRM Driver For Arm Mali Finally Seeing Run-Time Power Management

The Lima kernel driver providing reverse-engineered, open-source driver support for aging Arm Mali 4xx graphics processors is finally seeing run-time power management capabilities come Linux 5.8.

The run-time power management for the Mali 400 series hardware with this open-source DRM driver allows for letting the GPU suspend when idle for longer than 200ms. That 200ms threshold is also tunable via a new autosuspend_delay_ms value exposed on sysfs for the driver.

Current Lima driver developer Qiang Yu notes in his enablement work that the time to resume the GPU device is around 40us on an Allwinner H3 SoC and around 20us to suspend.

This work will provide some power-saving benefit for using the Lima driver stack on these older Mali GPUs.

The run-time power management support for Lima was sent in via the latest drm-misc-next patches that also include supporting more panels and other small changes to the different smaller DRM drivers. Those patches are queuing up for the forthcoming Linux 5.8 kernel.