[Intel-gfx] [PATCH v2 1/2] drm/i915/debugfs: Print sink PSR status

[Souza, Jose]

On Mon, 2018-04-02 at 15:38 -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 at 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.

In my tests(PSR1 only) with DMC loaded, I can see HW trigerring PSR
exit when reading i915_edp_psr_status with or without this patch, the
event that caused is 'SRD Mask Reg Write'.
After masking EDP_PSR_DEBUG_MASK_DISP_REG_WRITE in EDP_PSR_DEBUG it do
not happens with or without this patch.

Masking this event did not bring more IGT errors than we have now, what
do you think Dhinakaran? Should we mask it?

> 
> 
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at 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);