Bug#945618: regression: 5.3 and above kernels in Debian are not allowing Intel processor to enter package c states
package: src:linux
1. run powertop --auto-tune to ensure settings are optimal for power saving. This may require a laptop.
2. Run powertop, press tab, and notice that the values in pc2 through pc10 are not incrementing.
Reproduced on Broadwell and Whiskey Lake. The first version of 5.3 posted to experimental was fine but this regressed after that and it is still a problem in 5.4 in experimental. Also, things work fine in Arch kernel so its probably something with the Debian config. On a side note, if you want to test in Skylake or newer, you need the non-free firmware package for the Intel DMC firmware which allows the graphics controller to enter a low power state. I used to see pc8 on one of my machines and pc7 on the other as the lowest power states incrementing in Debian. These still increment in Arch with the latest Kernels. This bug results in a 5 degree c higher idle temperature on the Whiskey Lake machine.
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