Re: [PATCH 2/5] drm/i915: PSR: Remove Low Power HW tracking mask.

From: "Runyan, Arthur J" <arthur.j.runyan@intel.com>
To: Rodrigo Vivi <rodrigo.vivi@gmail.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
	Matthew Garrett <mjg59@srcf.ucam.orgviacodon.org.uk>,
	"Vivi, Rodrigo" <rodrigo.vivi@intel.com>
Subject: Re: [PATCH 2/5] drm/i915: PSR: Remove Low Power HW tracking mask.
Date: Mon, 22 Jun 2015 22:31:32 +0000	[thread overview]
Message-ID: <C7E999358BBE9E45938BA940F5F51108757B7DDD@fmsmsx116.amr.corp.intel.com> (raw)
In-Reply-To: <CABVU7+sgz=aex1NXio4J1pr97EYUuQ1PQw0Zm37A7wrw3mBz=Q@mail.gmail.com>

-- Daniel
>> I guess I don't really understand your description, but it does sound
>> strange ... runtime pm enabling from my patch is only about D3, power
>> well changes are still done. And as long as we have anything enabled
>> (even with PSR) we'll prevent D3.
>>
>> So the only thing I can think of is that somehow D3 wreaks something
>> in the PSR setup and that's causing issues. Unfortunately I have no
>> idea about our hw details around PSR and D3, so no idea. Maybe Art has
>> some?
>
-- Rodrigo
>I don't know this relation as well. When I found this LPSP maks that
>made PSR working it was totally by forcing all masks and start
>removing one by one up to the point that this Low Power something did
>the trick. At that time Artur had told about power well handling
>enabled, but now after Mathew reported that issue I noticed this Low
>power flag was also related to runtime PM...
>

Let me see if I understand what is happening.  Runtime PM seemed to cause PSR to miss some screen updates when you had LPSP masked, then you stopped masking  LPSP and it fixed the missing updates?
My first guess is that you are not in LPSP at this point, so removing the mask is effectively disabling PSR, which prevents PSR from missing screen updates.   Are you still getting good PSR residency with LPSP masked in this situation?  

The LPSP mask is only there fro debug.  We don't normally want PSR to enter without LPSP because there can be undesirable things like clocks stopping which could break the display audio controller and codec.
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