Improved Linux Power Savings For Intel Haswell/Broadwell Laptops In 2023

It's been just shy of ten years since Intel launched their Haswell processors that were very successful at the time and was followed by Broadwell. While Intel's open-source Linux driver engineers are primarily concentrated on recent and future Intel hardware platforms, occasionally there is an improvement worth mentioning for mature platforms like Haswell and Broadwell. A new patch series this week will help with some minor graphics power-savings for those still running a nearly decade old Intel Linux laptop.

Longtime Intel Linux graphics driver engineer Ville Syrjala sent out a patch series on Friday to get Panel Self Refresh (PSR) back into shape for Haswell and Broadwell. Panel Self Refresh is designed to help extend laptop battery life by allowing the refresh rate to be adjusted independently, such as to avoid refreshing the display if just a static image is being displayed / no changes to the frame-buffer. In turn some elements of the GPU can be powered down during PSR periods to reduce power use and possible thermal benefits as well. Panel Self Refresh PSR1 support debuted with Haswell while later generations have more advanced capabilities with PSR2.

Panel Self Refresh handling with the Intel Linux driver has long been a difficult affair due to hardware/driver issues and uncovering stability issues and other problems with some hardware configurations. For different generations and at different times with their i915 kernel driver they've had to disable/re-enable the PSR handling due to bugs. In 2023, the Haswell/Broadwell PSR1 support is taking a fresh attempt to be enabled with all known issues being taken care of.

Syrjala simply wrote in Friday's i915 driver patch series:

"Fix all the obvious issues affecting HSW/BDW PSR1 and restore it back to life."

We'll see how this round of review goes on the 13 patches, which culminate with PSR being restored by default for Haswell and Broadwell graphics. This is good news in any event for those still relying on a Haswell/Broadwell Linux laptop.