Linux 5.17 Is Bringing Big Improvements For AMD Hardware
Yesterday I wrote up the Linux 5.17 feature overview now that Linux 5.17-rc1 has been tagged, which marks the end of new features being accepted for this kernel. Linux 5.17 will now see weekly release candidates until the stable kernel is ready around the end of March. While it won't be the default kernel of Ubuntu 22.04 LTS, it should be for the likes of Fedora 36 and other spring Linux distribution releases and obviously the rolling kernels. Below is a look at the many AMD improvements to find with Linux 5.17.
First and most impactful, the new AMD P-State driver is merged. This is the driver developed by AMD in cooperation with Valve for improving the power efficiency on Linux compared to the generic ACPI CPUFreq driver. The AMD P-State driver relies upon ACPI Collaborative Processor Performance Controls (CPPC) exposed by the platform for making more fine-grained CPU frequency / performance state information available. Using AMD P-State with the Schedutil governor should lead to better performance than CPUFreq with Schedutil as commonly used today. I'll have fresh benchmarks of AMD P-State vs. ACPI CPUFreq with different governors and different hardware in the coming days on Phoronix. Due to ACPI CPPC dependence, AMD P-State only will work with Zen 2 and newer processors and CPPC must be enabled on the system.
There is also a lot of next-gen (Zen 4) processor work including SMCA updates and EDAC updates, including identifying Registered DDR5 (RDDR5) and Load Reduced DDR5 (LDDR5) memory types for reporting. Also useful is seeing k10 temperature reporting support merged ahead of time rather than after the fact as sadly has been common during Zen 1/2/3 for not seeing timely CPU temperature monitoring support... Hopefully the recent trend continues holding up for timely temperature sensor support.
AMD Smart Trace Buffer support is ready with Linux 5.17 both on the CPU side and with the Radeon dGPU side with newer hardware. AMD Smart Trace Buffer is basically a cyclic data buffer having log information about system execution for helping to analyze failures. The STB is always running and can be dumped when an error occurs without having to reproduce it or run any extra instrumentation.
AMD Renoir hardware now has Sound Open Firmware Support for its audio co-processor and is the first AMD platform supporting Sound Open Firmware for what originally started as an Intel project. Also on the AMD Linux laptop front there is an AMD s2idle failure fix, the latest in an array of S2idle / S0ix related AMD Linux work. Meanwhile many newer ASUS motherboards with X570/B550/B450/X470 chipsets now have working sensor support finally under Linux. Linux 5.17 also introduces Rembrandt SoC network support>
Over on the Radeon side of the house, there is GPU recovery support for Rembrandt APUs, Seamless Boot for Van Gogh, and bug fixes. The AMDGPU DRM kernel driver side wasn't as exciting this time around as some of the other recent kernel releases.
While not impactful for modern hardware, Linux 5.17 does retire AMD 3DNow! instruction usage from within the kernel code. Also on the older AMD hardware front, AMD Fusion APU systems with Hudson D4 chipsets may see a boot time improvement.
Stay tuned for Linux 5.17 kernel benchmarks ramping up on Phoronix over the days/weeks ahead.