On Fri, 2018-02-16 at 08:58 +0000, Chris Wilson wrote:
> Quoting Dhinakaran Pandiyan (2018-02-16 04:33:22)
> > With fbdev, screen freezes after a few continuous PSR exit->enter cycles.
> > Printing out the PSR status register clearly showed this freeze coincided
> > with exiting when the hardware is in a transitory state. So wait for a max
> > of 100 ms (~6 frames) for PSR to become active and then exit.
> >
> > Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_psr.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> > index 2a31c7cbdb41..d6669f5f890f 100644
> > --- a/drivers/gpu/drm/i915/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > @@ -738,6 +738,17 @@ static void intel_psr_exit(struct drm_i915_private *dev_priv)
> > WARN_ON(!(val & EDP_PSR2_ENABLE));
> > I915_WRITE(EDP_PSR2_CTL, val & ~EDP_PSR2_ENABLE);
> > } else {
> > + /* Wait for about 6 frames in case we just enabled PSR,
> > + * this prevents the screen from freezing as the HW does
> > + * not seem to be able to back off cleanly it is already
> > + * trying to enter PSR.
> > + */
> > + intel_wait_for_register(dev_priv,
> > + EDP_PSR_STATUS,
> > + EDP_PSR_STATUS_STATE_MASK,
> > + EDP_PSR_STATUS_STATE_SRDENT,
> > + 100);
>
> I'm going to suggest that you want a DRM_DEBUG_KMS() (_DRIVER? Not sure
> what works best for PSR/frontbuffer-tracking) at least for spotting
> trouble when it times out. I would start with a DRM_ERROR for a few CI
> passes just to see what's happening on our machines before toning it
> down for production.
Thanks for the suggestion, makes sense. I don't think we have a test to
emulate a blinking fbcon cursor, which happens to trigger continuous PSR
flushes. I'll look into it.
-DK
> -Chris
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