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

[Nagaraju, Vathsala]

Hi Shablin,

I will look In to it and provide the fix.

Regards,
Vathsala

From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org] On Behalf Of Yaroslav Shabalin
Sent: Tuesday, May 23, 2017 2:45 PM
To: intel-gfx at lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/psr: disable psr2 for resolution greater than 32X20

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.
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