With Linux 6.6, Intel Restoring Panel Self Refresh For Aging Haswell/Broadwell Laptops

It's been ten years since Intel launched the Haswell processors that were great for the time followed by Broadwell. On the laptop side for Haswell and Broadwell the Panel Self Refresh (PSR) power-savings support has been rather notorious at least on the Linux side. Finally for the Linux 6.6 kernel due out in late 2023, the developers are re-enabling PSR support for these aging laptops.

Panel Self Refresh is a power-savings feature that can lower device power by letting the laptop display panel refresh independently when the screen contents are static. Due to various hardware issues and quirks coming about, Panel Self Refresh for Haswell and Broadwell ended up getting disabled by the kernel due to these problems during the early times of PSR appearing on laptops.

Ten years after Haswell laptops first appeared, the outstanding PSR problems are believed to be addressed and thus the Intel Linux developers going ahead and re-enabling PSR1 for Haswell and Broadwell.

The re-enabling of PSR1 for HSW/BDW was sent in today as part of the drm-intel-next patches queuing in DRM-Next until the Linux 6.6 cycle kicks off in a few weeks. This week's Intel i915 DRM driver pull also has other PSR fixes, HDCP improvements, continued fixes around Meteor lake display handling, and other general driver fixes and enhancements.

Flipping Panel Self Refresh on for Haswell/Broadwell is just a few lines of codes to set the "has_psr" and "has_psr_hw_tracking" bits so in the event of problems down the road it will be easy for kernel developers to disable this power-savings feature should all bugs not be ironed out.