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: Tue, 23 Jun 2015 18:40:02 +0000	[thread overview]
Message-ID: <C7E999358BBE9E45938BA940F5F51108757B88D2@fmsmsx116.amr.corp.intel.com> (raw)
In-Reply-To: <CABVU7+uXV-E1ML-e1jkynCrGeb38ZfC6B0fw3eOY1NEUPK8oPw@mail.gmail.com>

>From: Rodrigo Vivi [mailto:rodrigo.vivi@gmail.com] 
>>On Mon, Jun 22, 2015 at 3:31 PM Runyan, Arthur J <arthur.j.runyan@intel.com> wrote:
>>-- 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?
>Yes.
 
>>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?
>Without LPSP masked residency is 0 until I enable runtime_pm from i915 and audio. But once they get enabled residency counter increases fast.
It sounds like you aren't really getting LPSP without runtime_pm.  Probably because the audio codec has to be in D3 to allow LPSP.  So I think this is a general problem with missing screen updates when PSR is entered, and the runtime_pm is modulating when PSR can be entered.  
Do you have a case where PSR residency is increassing and the screen updates are not missed?
Are these flips or are they front buffer modifications?

>Also if I have wireless searching for network or trying to connect residency stay 0, but once connection gets stablished or stop trying to connect than PSR residency start increasing again.
The wireless searching is causing frequent flips or other screen udpates?  
Also the residency counter measurement of time is not accurate since it doesn't account for time when clocks get stopped, but you should see it making some progress if PSR is really entered.

>>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.
>Yeah, I know. I just masked because I could never get PSR count bigger than 0 without this mask previously...
 
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