Hi!
I have Dell XPS 15 9550 with Skylake i7-6700HQ CPU, 4K screen resolution (3840x2160) and Arch Linux installed. Adding i915.enable_psr=1 boot parameter on kernels <= 4.10 I get the following:
-> cat /sys/kernel/debug/dri/0/i915_edp_psr_status
Sink_Support: yes
Source_OK: yes
Enabled: yes
Active: yes
Busy frontbuffer bits: 0x000
Re-enable work scheduled: no
Main link in standby mode: no
HW Enabled & Active bit: yes
However on kernel 4.11 (which I believe has this commit merged) PSR is not enabled with native screen resolution.
-> cat /sys/kernel/debug/dri/0/i915_edp_psr_status
Sink_Support: yes
Source_OK: no
Enabled: no
Active: no
Busy frontbuffer bits: 0x000
Re-enable work scheduled: no
Main link in standby mode: no
HW Enabled & Active bit: no
If I change resolution to lower value (i.e. 3200x1800) PSR gets enabled as on <= 4.10 kernel.
That is very sad because without PSR CPU never goes deeper than PC7 adding ~1W to idle power consumption. I would really appreciate if someone investigate this issue. Is this resolution restriction really needed and should block PSR fully? Seems that on older kernels it wasn't a problem. Please let me know if you need any additional diagnostic information.
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