[Intel-gfx] [PATCH] drm/i915/psr: disable psr2 for resolution greater than 32X20

[Yaroslav Shabalin]

Hi!

I'm not sure if this is suitable way to report bugs but seems that this
change (
https://github.com/torvalds/linux/commit/acf45d11050abd751dcec986ab121cb2367dcbba)
breaks PSR support on my laptop.
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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx/attachments/20170523/ffec30be/attachment.html>