AMD Has An Important Suspend/Resume Fix With Linux 5.15

Since last year AMD has been working to get its s2idle / suspend-to-idle S0ix sleep state code in order for supporting this lowest power platform idle state on newer AMD laptops and there has also been other AMD suspend/resume improvements in recent times. Now with the Linux 5.15 kernel cycle is an important fix for the AMD s2idle code.

Stemming from a user reporting incorrect resume from suspend with an HP ENVY X360, Linux 5.15 has a fix for it and other laptops facing a similar problem. The original issue was resuming from suspend would yield the power LED not working, some keys like brightness controls not working, and the cooling fan not spinning up even under load. Yeah, that's quite a poor Linux laptop experience.

Sent in to Linux 5.15 today as part of more ACPI updates is changing around the suspend-to-idle support code to meet the platform firmware expectations on some AMD systems.

While debugging the problem of the HP ENVY X360 laptop going awry after resume, AMD checked with their internal team and discovered that under Windows both the AMD and Microsoft methods need to be called. Previously just the Microsoft method was called when present on Linux systems. Many OEM systems though don't implement anything for the AMD methods but some do as in the case of this HP laptop and so the s2idle code now will be calling both the Microsoft and AMD methods when present. This at least gets the HP ENVY X360 to behave now on resume and we'll see soon enough what other hardware similarly benefits from this change.

This AMD s2idle patch for Linux 5.15 was written by Mario Limonciello, a recent and prominent hire to AMD's Linux client team.