AMDGPU With Linux 5.12 Sees Last Minute Duty Cycle Scaling, Other Bits

Sent in last week were some AMDGPU "fixes" for Linux 5.12. While there are some fixes as part of the series, there are some new (minor) features enabled.

In addition to the previously covered DRM graphics driver features for Linux 5.12 like the Radeon RX 6000 series OverDrive, there are some more patches that were sent in last Thursday as fixes for Linux 5.12.

From that pull are some more AMDGPU changes worth mentioning for this next version of the Linux kernel:

- Enabling graphics wave limiting for high priority compute jobs. This should help ensure high priority compute jobs are allocated more resources to finish early.

- Enabling of Graphics Duty Cycle Scaling (DCS) for small power limit SKUs. This is about turning off the GPU ever so briefly when under heavy load. Duty Cycle Scaling is enable for these small GPUs when the current/power/temperature limits are exceeded. The graphics core gets powered off and then back on, based on the firmware determination. The initial AMDGPU kernel driver is supporting just Async DCS and not the frame-aligned DCS where this behavior could happen under 3D full-screen and VR workloads.

- Working to support Active State Power Management (ASPM) and Latency Tolerance Reporting (LTR) for Sienna Cichlid (Radeon RX 6800) and future GPUs. While ASPM can be useful for conserving power when idle, the ASPM support for Sienna Cichlid and future hardware is currently not enabled by default unless booting with amdgpu.aspm=1.

- LCLK Deep Sleep is now enabled when ASPM is enabled for greater power savings.

- Software SMU "swSMU" fixes for Sienna Cichlid, Renoir, and the forthcoming Van Gogh.

- Enabling of the "ACDC" feature on mobile Radeon GPUs where the power limit and clock range are different depending upon whether the laptop is operating in AC or DC power mode. With the feature bit enabled, the firmware takes control of handling the feature.

- GPU recovery support for the yet to be released "Dimgrey Cavefish" GPU.

- With forthcoming Van Gogh APUs is support for the user to control the slow/fast Package Power Tracking (PPT) via the HWMON sysfs. Manipulating the PPT can be done to maximize the APU within a given system power budget.

- Various fixes.