[Intel-gfx] [PATCH 4/4] drm/i915: Make sure PSR is ready for been re-enabled.

[Rodrigo Vivi]

Yeah, this is true. I'm going to send a v2 with 50ms timeout. I forgot that.

I sign up Paulo for this review! :)

On Wed, Sep 17, 2014 at 8:50 AM, Daniel Vetter <daniel at ffwll.ch> wrote:

> On Tue, Sep 16, 2014 at 07:19:08PM -0400, Rodrigo Vivi wrote:
> > Let's make sure PSR is propperly disabled before to re-enabled it.
> >
> > According to Spec, after disabled PSR CTL, the Idle state might occur
> > up to 24ms, that is one full frame time (1/refresh rate),
> > plus SRD exit training time (max of 6ms),
> > plus SRD aux channel handshake (max of 1.5ms).
> >
> > So if something went wrong PSR will be disabled until next full
> > enable/disable setup.
> >
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> > index 2f0eee5..658a911 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1885,6 +1885,17 @@ static void intel_edp_psr_do_enable(struct
> intel_dp *intel_dp)
> >       WARN_ON(dev_priv->psr.active);
> >       lockdep_assert_held(&dev_priv->psr.lock);
> >
> > +     /* We have to make sure PSR is ready for re-enable
> > +      * otherwise it keeps disabled until next full enable/disable
> cycle.
> > +      * PSR might take up to 24 ms to get fully disabled
> > +      * and be ready for re-enable.
> > +      */
> > +     if (wait_for((I915_READ(EDP_PSR_STATUS_CTL(dev)) &
>
> 24ms = frametime for roughly 40Hz. Looks awfully like something Bspec
> authors just pulled out of thin air.
>
> Generally our timeout for waiting for one vblank is 50ms (20Hz, which is a
> lot less than any sane panel does even with DRRS).
>
> Overall series looks sane, please sign someone up for detailed review.
>
> Thanks, Daniel
>
> > +                   EDP_PSR_STATUS_STATE_MASK) == 0, 24)) {
> > +             DRM_ERROR("Timed out waiting for PSR Idle for
> re-enable\n");
> > +             return;
> > +     }
> > +
> >       /* Enable/Re-enable PSR on the host */
> >       intel_edp_psr_enable_source(intel_dp);
> >
> > --
> > 1.9.3
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>



-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br
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