Re: [PATCH 2/4] drm/i915: Disable PSR when a PSR aux error happen

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Mon, 2018-10-08 at 17:30 -0700, Souza, Jose wrote:
> On Mon, 2018-10-08 at 17:14 -0700, Dhinakaran Pandiyan wrote:
> > On Fri, 2018-10-05 at 16:35 -0700, José Roberto de Souza wrote:
> > > While PSR is active hardware will do aux transactions by it self
> > > to
> > > wakeup sink to receive a new frame when necessary. If that
> > > transaction is not acked by sink, hardware will trigger this
> > > interruption.
> > > 
> > > So let's disable PSR as it is a hint that there is problem with
> > > this
> > > sink.
> > > 
> > > The removed FIXME was asking to manually train the link but we
> > > don't
> > > need to do that as by spec sink should do a short pulse when it
> > > is
> > > out of sync with source, we just need to make sure it is awaken
> > > and
> > > the SDP header with PSR disable will trigger this condition.
> > 
> > That's a good point, the short pulse handler does handle
> > retraining.
> > 
> > > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.h  |  1 +
> > >  drivers/gpu/drm/i915/intel_psr.c | 39
> > > ++++++++++++++++++++++++++++
> > > ----
> > >  2 files changed, 36 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > > b/drivers/gpu/drm/i915/i915_drv.h
> > > index 794a8a03c7e6..efbebe1c2ba3 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -638,6 +638,7 @@ struct i915_psr {
> > >  	u8 sink_sync_latency;
> > >  	ktime_t last_entry_attempt;
> > >  	ktime_t last_exit;
> > > +	u32 irq_aux_error;
> > >  };
> > >  
> > >  enum intel_pch {
> > > diff --git a/drivers/gpu/drm/i915/intel_psr.c
> > > b/drivers/gpu/drm/i915/intel_psr.c
> > > index cd9a60d1efa1..74090fffea23 100644
> > > --- a/drivers/gpu/drm/i915/intel_psr.c
> > > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > > @@ -159,10 +159,16 @@ void intel_psr_irq_handler(struct
> > > drm_i915_private *dev_priv, u32 psr_iir)
> > >  			       BIT(TRANSCODER_C);
> > >  
> > >  	for_each_cpu_transcoder_masked(dev_priv, cpu_transcoder,
> > > transcoders) {
> > > -		/* FIXME: Exit PSR and link train manually when this
> > > happens. */
> > > -		if (psr_iir & EDP_PSR_ERROR(cpu_transcoder))
> > > -			DRM_DEBUG_KMS("[transcoder %s] PSR aux
> > > error\n",
> > > -				      transcoder_name(cpu_transcoder));
> > > +		if (psr_iir & EDP_PSR_ERROR(cpu_transcoder)) {
> > > +			DRM_WARN("[transcoder %s] PSR aux error\n",
> > > +				 transcoder_name(cpu_transcoder));
> > > +
> > > +			spin_lock(&dev_priv->irq_lock);
> > > +			dev_priv->psr.irq_aux_error |=
> > > BIT(cpu_transcoder);
> > > +			spin_unlock(&dev_priv->irq_lock);
> > > +
> > > +			schedule_work(&dev_priv->psr.work);
> > > +		}
> > >  
> > >  		if (psr_iir & EDP_PSR_PRE_ENTRY(cpu_transcoder)) {
> > >  			dev_priv->psr.last_entry_attempt = time_ns;
> > > @@ -891,11 +897,36 @@ int intel_psr_set_debugfs_mode(struct
> > > drm_i915_private *dev_priv,
> > >  	return ret;
> > >  }
> > >  
> > > +static void intel_psr_handle_irq(struct drm_i915_private
> > > *dev_priv)
> > > +{
> > > +	struct i915_psr *psr = &dev_priv->psr;
> > > +	u32 irq_aux_error;
> > > +
> > > +	spin_lock_irq(&dev_priv->irq_lock);
> > > +	irq_aux_error = psr->irq_aux_error;
> > > +	psr->irq_aux_error = 0;
> > > +	spin_unlock_irq(&dev_priv->irq_lock);
> > > +
> > > +	/* right now PSR is only enabled in eDP */
> > > +	WARN_ON(irq_aux_error & ~BIT(TRANSCODER_EDP));
> > > +
> > > +	mutex_lock(&psr->lock);
> > > +
> > > +	intel_psr_disable_locked(psr->dp);
> > > +	/* let's make sure that sink is awaken */
> > > +	drm_dp_dpcd_writeb(&psr->dp->aux, DP_SET_POWER,
> > > DP_SET_POWER_D0);
> > 
> > We should be making sure the sink exits PSR after psr_invalidate()
> > ->
> > psr_exit() too? Which means, we have to figure out a cleaner way to
> > handle all of this. I am not sure, at this point, what a cleaner
> > solution will like. However, I'd like PSR disable from invalidate,
> > PSR
> > disable from a modeset and PSR disable due to an error share code
> > and
> > behavior. All of them should basically be
> > 1) Disable PSR in PSR_CTL
> > 2) Wait for idle in PSR_STATUS
> > 3) Write to sink DP_SET_POWER
> 
> We don't need to wait PSR to be disabled for invalidate(), hardware
> will do the exit sequence including write to DP_SET_POWER, also in
> this
Yeah, but doesn't work consistently on the panel that I have, writing
to the sink DP_SET_POWER dpcd is needed. I guess, we could add a panel
specific quirk to work around it.

-DK

> case we want activate PSR as soon as all frontbuffer changes was
> commited and PSR is inactive.
> 

> > 
> > 
> > 
> > > +
> > > +	mutex_unlock(&dev_priv->psr.lock);
> > > +}
> > > +
> > >  static void intel_psr_work(struct work_struct *work)
> > >  {
> > >  	struct drm_i915_private *dev_priv =
> > >  		container_of(work, typeof(*dev_priv), psr.work);
> > >  
> > > +	if (READ_ONCE(dev_priv->psr.irq_aux_error))
> > > +		intel_psr_handle_irq(dev_priv);
> > > +
> > >  	mutex_lock(&dev_priv->psr.lock);
> > >  
> > >  	if (!dev_priv->psr.enabled)

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