SLPC-Based Power Management Still Being Worked On For Intel's DRM Driver
Written by Michael Larabel in Intel on 9 September 2016 at 10:00 AM EDT. 3 Comments
INTEL --
The Single Loop Power Controller (SLPC) was an interesting addition to Skylake hardware but even with Skylake processors being out more than one year and the SLPC patches for the Intel DRM Linux driver having been out for a number of months, this GuC-based SLPC support has yet to be merged. The latest version of the patches was just published.

For those that don't recall what SLPC is about, read Intel's Linux GPU Driver Is Working To Move More Power Management Handling To Firmware. It basically comes down to the SLPC running on the GuC firmware to replace some host-based power management features of the Intel graphics hardware.

In terms of the benefits of SLPC, Sagar Arun Kamble of Intel commented on the latest patches, "Performance and power testing(SKL) with these patches and 9.18 firmware is at parity and in some cases better than host RPS today on various Linux benchmarks."

GuC/SLPC is present on just Skylake and newer hardware, with these current DRM patches being about supporting the Single Loop Power Controller for Skylake and Broxton graphics hardware. This SLPC support obviously requires the use of the GuC firmware binary blobs that have upset some users with Intel graphics hardware beginning to make use of these binary-only firmware bits not being free software. This version of the patches in fact is just compatible with a newer version of the firmware blobs that has yet to be publicly released.

Those wishing to learn more can see the message at the beginning of the latest patch series. The 26 patches for this GuC-based SLPC power management support add over 1300 lines of new code to the i915 DRM kernel driver. We'll see if this support gets wrapped up for Linux 4.9 or is staved off for yet another kernel cycle.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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