AMDGPU In Linux 4.17 Exposes WattMan Features, GPU Voltage/Power Via Hwmon

Written by Michael Larabel in Radeon on 23 February 2018 at 04:00 PM EST. 16 Comments
AMD's Alex Deucher today sent in the first pull request to DRM-Next of AMDGPU (and Radeon) DRM driver feature material that will in turn be merged with the Linux 4.17 kernel down the road. There's some fun features for AMDGPU users coming with this next kernel!

First up, Linux is finally getting some WattMan-like functionality after it's been available via the Windows Radeon Software driver since 2016. WattMan allows for more fine-tuning of GPU clocks, voltages, and more for trying to maximize the power efficiency. See the aforelinked article for details but currently without any GUI panel for tweaking all of the driver tunables, this WattMan-like support needs to be toggled from the command-line.

Related to the WattMan work, thermal thresholds are now exposed through the hwmon interfaces. Also, the GPU voltage and power use is also exposed via the hwmon interfaces too. There is also initial support for power profiles for use-case optimized performance.

AMDGPU DC (display code) has seen more updates for this cycle and so far includes some code clean-ups, improved dual-link DVI handling, CRC support, and gamma / color management support.

On the APU side, AMDGPU now supports scanning out from system memory on Carrizo, Bristol Ridge, and Stoney hardware. Other changes include reworking HDP flushing for rings and CPU, reworking GPUVM TLB flushing, and reworking IP offset handling for SOC15 hardware. There are also a number of TTM memory management clean-ups and improvements as well as better handling in out-of-memory cases.

It's great to see all this feature activity for AMDGPU DRM-Next, especially the power/performance features. Though no explicit word on any Raven Ridge support improvements, but I will be trying this code in the days ahead. The complete list of AMDGPU changes for this initial DRM-Next pull request can be found on dri-devel.
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