[PATCH 2/5] drm/i915: keep AUX powered while PSR is enabled

[Rodrigo Vivi]

On Tue, Feb 13, 2018 at 08:45:54PM +0000, Souza, Jose wrote:
> On Mon, 2018-02-12 at 23:26 -0800, Rodrigo Vivi wrote:
> > On Tue, Feb 13, 2018 at 12:16:10AM +0000, José Roberto de Souza
> > wrote:
> > > Hardware can send AUX transactions by it self when PSR is enabled
> > > and it
> > > expects that AUX is kept powered up.
> > > 
> > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_psr.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_psr.c
> > > b/drivers/gpu/drm/i915/intel_psr.c
> > > index 8b456e4e1b47..225fde979e57 100644
> > > --- a/drivers/gpu/drm/i915/intel_psr.c
> > > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > > @@ -516,6 +516,12 @@ void intel_psr_enable(struct intel_dp
> > > *intel_dp,
> > >  		goto unlock;
> > >  	}
> > >  
> > > +	/*
> > > +	 * hardware can send AUX transactions by it self when PSR
> > > is enabled,
> > > +	 * and it expects that AUX is kept powered up.
> > > +	 */
> > > +	intel_display_power_get(dev_priv, intel_dp-
> > > >aux_power_domain);
> > > +
> > 
> > we actually kind of need the other way around... we need a way to
> > block psr on aux transactions
> > instead of making sure we have more power wells enabled when psr is
> > enabled.
> > 
> > this approach here would kill some power savings
> 
> I agree that it will kill some of the power savings but when enabling
> or disabling PSR hardware will do some aux transactions by it self, so
> we need to guarantee that the power wells that have the aux ch is kept
> powered otherwise hardware will not be able to do the aux ch
> transactions.

Display engine should takes care of this by itself. We are not required
to leave power wells on for PSR to work.

> 
> > 
> > >  	dev_priv->psr.psr2_support = crtc_state->has_psr2;
> > >  	dev_priv->psr.busy_frontbuffer_bits = 0;
> > >  
> > > @@ -656,6 +662,8 @@ void intel_psr_disable(struct intel_dp
> > > *intel_dp,
> > >  	/* Disable PSR on Sink */
> > >  	drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG, 0);
> > >  
> > > +	intel_display_power_put(dev_priv, intel_dp-
> > > >aux_power_domain);
> > > +
> > >  	dev_priv->psr.enabled = NULL;
> > >  	mutex_unlock(&dev_priv->psr.lock);
> > >  
> > > -- 
> > > 2.16.1
> > > 
> > 
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