[Intel-gfx] proposal for DVFS (Dynamic Voltage Frequency Scaling)

[Thulasimani, Sivakumar]

Thanks for the suggestion Daniel, this seems simpler solution to the problem. I'll check for corner cases and get back if any more changes are needed.


regards,
Sivakumar

-----Original Message-----
From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
Sent: Wednesday, February 11, 2015 2:24 PM
To: Thulasimani, Sivakumar
Cc: Daniel Vetter; intel-gfx at lists.freedesktop.org; Purushothaman, Vijay A
Subject: Re: [Intel-gfx] proposal for DVFS (Dynamic Voltage Frequency Scaling)

On Wed, Feb 11, 2015 at 09:51:53AM +0100, Daniel Vetter wrote:
> On Wed, Feb 11, 2015 at 08:32:59AM +0000, Thulasimani, Sivakumar wrote:
> > Hi All,
> > 	I went through Ville's changes and it seems to be lacking support 
> > for our one  main user experience requirement in Android. Which is as follows "Ux Restrictions:  Flash/flicker should be avoided as much as possible( i.e during unplug of HDMI avoid immediately lowering the CD clock after hotunplug since it will result in flicker on LFP )."
> > The display will be turned off eventually (especially considering Android) and would be good to change the CD clock at this point in time rather than immediately on hot unplug. So we have to add to current implementation to modify the behavior or go with the HWC+driver logic described below. 
> 
> Hm yeah. But for upstreaming can we just start with Ville's patch 
> series to get things going?

Thinking about this a bit more it's easy to implement your desired behaviour just in hwc:

- On unplug of hdmi only do a dpms off for that hdmi output/crtc. That way
  the kernel will keep all allocations/requirements and hence also cdclock
  high.

- When you power off the panel with dpms off, then you can do the
  setCrtc(off) to release resources and clock down cdclock.

So no real changes required on the kernel side imo.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch