Issue or bug concerning DRRS on old i7-4980HQ

[René Herman]

Hello all.

Addresses as per MANTAINERS, and Ville as per Git history...

I've been trying to assist a new Linux user with an old 2015 Alienware 
17 R2, i7-4980HQ (Iris Pro 5200) together with NVIDIA GTX980M.

The user experienced flickering (in a brightness sense) and had traced 
this back to Intel DRRS. I supplied a simple test patch as

--- linux-6.8.0/drivers/gpu/drm/i915/display/intel_dp.c.orig	
+++ linux-6.8.0/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2727,6 +2727,8 @@
  {
  	struct drm_i915_private *i915 = to_i915(connector->base.dev);

+	return false;
+
  	if (pipe_config->vrr.enable)
  		return false;

which does indeed work. Set out to then solve it right(er) and ran into 
the debugfs drrs ctl file, for him

/sys/kernel/debug/dri/1/crtc-0/i915_drrs_ctl

We haven't however been able to do anything useful with that. If we echo 
0 into it it seems that DRRS does temporarily go to "DRRS active: no" in 
the corresponding i915_drrs_status file, but only seconds later it again 
shows as "DRRS active: yes", and his problem returns/remains.

It's making the system largely unusable with Linux -- or are we/am I 
missing something as to configuration?

The user is as said a new Linux user and will need to stick with generic 
distribution kernels, Ubuntu here, but the debugfs thing seems to then 
not work and a kernel parameter appears to not exist. When searching I 
found this issue also at for example

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1928138

and on the list at

https://lists.freedesktop.org/archives/intel-gfx/2017-October/145050.html

Is there something we/he could do to get DRRS disabled with a generic 
distribution kernel? Should the i915_drrs_ctl thing have worked?

And if not, is there a possibility for a kernel parameter that does 
something akin to that above working test patch (but then right)?

Kind regards,
Rene Herman