[PATCH 3/3] DRI2: defer swap if relevant CRTC is in DMPS off state

[Michel Dänzer]

On Fre, 2012-12-14 at 12:03 -0500, Ilija Hadzic wrote: 
> On Fri, Dec 14, 2012 at 4:55 AM, Michel Dänzer <michel at daenzer.net> wrote:
> >> +    /*
> >> +     * CRTC is in DPMS off state, fallback to blit, but pace the
> >> +     * application at the rate that roughly approximates the
> >> +     * nominal frame rate of the relevant CRTC
> >> +     */
> >> +    if (!radeon_crtc_is_enabled(crtc)) {
> >> +     TimerSet(NULL, 0, nominal_vblank_period, radeon_dri2_deferred_swap,
> >> +              swap_info);
> >> +     *target_msc = 0;
> >> +     return TRUE;
> >> +    }
> >
> > This will always wait for (at least) nominal_vblank_period milliseconds
> > before performing the swap, but a significant part of that (or even more
> > time) might have passed already since the last swap of the drawable. You
> > could keep track of the previous swap time (from the event tv_(u)sec
> > values or GetTimeInMillis()) in a drawable private and only wait for the
> > amount of time actually necessary.
> 
> I guess you mean CRTC private.

I mean what I wrote.

> There is no drawable private

So add one.

> and such information would not be per-drawable anyway (it would be per-CRTC).

Eh? The MSC and related values are properties of the drawable, not the
CRTC (there is no concept of a CRTC in GLX/DRI2 at all). Only tracking
this per CRTC will break with several clients synchronizing to the same
CRTC.


> Regarding taking target_msc into account, I agree, but I have a
> question: is setting
> target_msc to zero (to return it to the caller) acceptable action ? As
> far as I can tell,
> it should be fine: if schedule_swap resets target_msc, in the next
> call the caller
> "resynchronizes"  (i.e. if I return zero in current call, it will
> typically be 1 in the next call).

I don't know all the ramifications, but can't you just leave it (or
maybe update it to reflect the current fake MSC, at least if we missed
the target)?


-- 
Earthling Michel Dänzer           |                   http://www.amd.com
Libre software enthusiast         |          Debian, X and DRI developer