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

[Rodrigo Vivi]

On Tue, Jun 23, 2015 at 11:40 AM Runyan, Arthur J <arthur.j.runyan at intel.com>
wrote:

> >From: Rodrigo Vivi [mailto:rodrigo.vivi at gmail.com]
> >>On Mon, Jun 22, 2015 at 3:31 PM Runyan, Arthur J <
> arthur.j.runyan at 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.
>

I believe this address Daniel's doubt. So we are fine and we need this
patch if runtime_pms are enabled otherwise PSR wont work.


> Do you have a case where PSR residency is increassing and the screen
> updates are not missed?
>

yes, with runtime_pm enabled (auto) on i915 and on audio and no wireless
activity PSR residency increases and we don't miss any screen update.


> Are these flips or are they front buffer modifications?
>

The reported issue when LPSP is masked and runtime_pm is working is with
frontbuffer 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?
>

(Witout LPSP mask and rutime_pm enabled) The wireless search blocks PSR
residency on 0. But screen updates happen normally as expected. When it
stop trying connecting residency start increasing and screen updates still
work as expected.


> 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.
>

Yeah, it works as expected.


>
> >>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...
>
>

Thanks,
Rodrigo.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20150623/e6b89ba1/attachment.html>