Re: [PATCH v2 1/2] drm/i915/debugfs: Print sink PSR status

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Apr 02, 2018 at 03:38:26PM -0700, Pandiyan, Dhinakaran wrote:
> On Mon, 2018-04-02 at 13:51 -0700, José Roberto de Souza wrote:
> > IGT tests could be improved with sink status, knowing for sure that
> > hardware have activate or exit PSR.
> > 
> > Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> 
> 
> Please don't merge this patch yet. While the patch itself is correct,
> testing it brings up an interesting problem.
> 
> Printing the sink_status() leads to power_get(aux_domain) which wakes up
> the display engine from DC5/6. This results in a HW triggered PSR exit,
> effectively altering the state that we are trying to read. I would like
> to understand the problem fully before merging the patch.

ack

> 
> 
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 29 +++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 1dba2c451255..c9ac946b62c9 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -2603,6 +2603,26 @@ static const char *psr2_live_status(u32 val)
> >  	return "unknown";
> >  }
> >  
> > +static const char *psr_sink_status(u8 val)
> > +{
> > +	static const char * const sink_status[] = {
> > +		"inactive",
> > +		"transition to active, capture and display",
> > +		"active, display from RFB",
> > +		"active, capture and display on sink device timings",
> > +		"transition to inactive, capture and display, timing re-sync",
> > +		"reserved",
> > +		"reserved",
> > +		"sink internal error"
> > +	};
> > +
> > +	val &= DP_PSR_SINK_STATE_MASK;
> > +	if (val < ARRAY_SIZE(sink_status))
> > +		return sink_status[val];
> > +
> > +	return "unknown";
> > +}
> > +
> >  static int i915_edp_psr_status(struct seq_file *m, void *data)
> >  {
> >  	struct drm_i915_private *dev_priv = node_to_i915(m->private);
> > @@ -2684,6 +2704,15 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
> >  		seq_printf(m, "EDP_PSR2_STATUS: %x [%s]\n",
> >  			   psr2, psr2_live_status(psr2));
> >  	}
> > +
> > +	if (dev_priv->psr.enabled) {
> > +		struct drm_dp_aux *aux = &dev_priv->psr.enabled->aux;
> > +		u8 val;
> > +
> > +		if (drm_dp_dpcd_readb(aux, DP_PSR_STATUS, &val) == 1)
> > +			seq_printf(m, "Sink PSR status: 0x%x [%s]\n", val,
> > +				   psr_sink_status(val));
> > +	}
> >  	mutex_unlock(&dev_priv->psr.lock);
> >  
> >  	intel_runtime_pm_put(dev_priv);
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