Power Management Bugs Hold Up Some Linux Laptops Due To Regulatory Requirements
A new Linux kernel patch series sent out today seeks to improve system power consumption at S5. Mario Limonciello of the AMD Linux engineering team explained in that patch series:
"OEM systems that ship with Linux preloaded need to go through energy certifications that match regulatory bodies in the regions that they will ship.
If any of those certifications don't pass then OEMs might not be able to ship systems preloaded in applicable regions.
Multiple models of systems are reported to fail in Linux but pass for Windows on the exact same hardware.
By looking at a breakdown of power consumption across devices the issue is that some devices aren't turned off when user puts the system into S5.
This series modifies the PCI driver and PCIe port shutdown codepaths to ensure that devices aren't needlessly woken up and that the hierarchy for all ports is put into D3cold.
With this series power consumption at S5 drops on some affected systems to ranges that should be acceptable to ship preloaded."
Simply put, Linux on some newer laptops are not currently meeting necessary regulatory certifications but behave fine on Windows. This can come down to platform firmware differences and other behavior differences between the Windows and Linux kernels.
While no particular hardware is explicitly noted in the patch series, it would appear to be at least some Lenovo laptops. And with AMD working on these S5 system power consumption improvements, presumably is affecting at least AMD Ryzen laptop models. The S5 enhancements are being made to the common PCI driver common code when hitting S5. Linux power management subsystem maintainer Rafael Wysocki has questioned some elements of the patch series so we'll see ultimately how this work evolves into a solution that can be accepted upstream in the Linux kernel to rectify some Linux laptops not meeting regulatory certifications.
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