[Intel-gfx] [PATCH v2 3/8] drm/i915/psr: Avoid initializing PSR if there is no sink support.

[Pandiyan, Dhinakaran]

On Wed, 2018-01-03 at 13:59 -0800, Rodrigo Vivi wrote:
> first of all sorry for not getting back sooner on this...
> 
> On Tue, Dec 19, 2017 at 09:40:01PM +0000, Pandiyan, Dhinakaran wrote:
> > 
> > 
> > 
> > On Tue, 2017-12-19 at 13:29 -0800, Rodrigo Vivi wrote:
> > > On Tue, Dec 19, 2017 at 05:26:54AM +0000, Dhinakaran Pandiyan wrote:
> > > > DPCD read for the eDP is complete by the time intel_psr_init() is
> > > > called, which means we can avoid initializing PSR structures and state
> > > > if there is no sink support.
> > > > 
> > > > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/i915_debugfs.c | 7 ++++++-
> > > >  drivers/gpu/drm/i915/intel_psr.c    | 9 +++++++++
> > > >  2 files changed, 15 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > > > index 64e5a263458c..1a7b28f62570 100644
> > > > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > > > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > > > @@ -2532,14 +2532,19 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
> > > >  	u32 stat[3];
> > > >  	enum pipe pipe;
> > > >  	bool enabled = false;
> > > > +	bool sink_support;
> > > >  
> > > >  	if (!HAS_PSR(dev_priv))
> > > >  		return -ENODEV;
> > > >  
> > > > +	sink_support = dev_priv->psr.sink_support;
> > > > +	seq_printf(m, "Sink_Support: %s\n", yesno(sink_support));
> > > > +	if (!sink_support)
> > > > +		return 0;
> > > > +
> > > >  	intel_runtime_pm_get(dev_priv);
> > > >  
> > > >  	mutex_lock(&dev_priv->psr.lock);
> > > > -	seq_printf(m, "Sink_Support: %s\n", yesno(dev_priv->psr.sink_support));
> > > >  	seq_printf(m, "Enabled: %s\n", yesno((bool)dev_priv->psr.enabled));
> > > >  	seq_printf(m, "Active: %s\n", yesno(dev_priv->psr.active));
> > > >  	seq_printf(m, "Busy frontbuffer bits: 0x%03x\n",
> > > > diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> > > > index 76339cf387cb..095e0a5a8574 100644
> > > > --- a/drivers/gpu/drm/i915/intel_psr.c
> > > > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > > > @@ -503,6 +503,9 @@ void intel_psr_enable(struct intel_dp *intel_dp,
> > > >  	if (!crtc_state->has_psr)
> > > >  		return;
> > > >  
> > > > +	if (WARN_ON(!CAN_PSR(dev_priv)))
> > > > +		return;
> > > 
> > > hmm... I believe we will see this warning sooner than later...
> > > 
> > > has_psr is not the same as CAN_PSR.
> > 
> > has_psr should not be set in psr_compute_config() unless both source and
> > sink have PSR. So, the warn_on is if we mess up the state preparation.
> > > 
> > > also, btw I didn't like all this crtc_state has_psr x has_psr2. :/
> > > 
> > > probably this series could also unify that and clean it up.
> > > to many has_psr like cases.
> > > 
> > > > +
> > > >  	WARN_ON(dev_priv->drrs.dp);
> > > >  	mutex_lock(&dev_priv->psr.lock);
> > > >  	if (dev_priv->psr.enabled) {
> > > > @@ -633,6 +636,9 @@ void intel_psr_disable(struct intel_dp *intel_dp,
> > > >  	if (!old_crtc_state->has_psr)
> > > >  		return;
> > > >  
> > > > +	if (WARN_ON(!CAN_PSR(dev_priv)))
> > > > +		return;
> > > > +
> > > >  	mutex_lock(&dev_priv->psr.lock);
> > > >  	if (!dev_priv->psr.enabled) {
> > > >  		mutex_unlock(&dev_priv->psr.lock);
> > > > @@ -913,6 +919,9 @@ void intel_psr_init(struct drm_i915_private *dev_priv)
> > > >  	dev_priv->psr_mmio_base = IS_HASWELL(dev_priv) ?
> > > >  		HSW_EDP_PSR_BASE : BDW_EDP_PSR_BASE;
> > > >  
> > > > +	if (!dev_priv->psr.sink_support)
> > > > +		return;
> > > > +
> > > 
> > > Why not use CAN_PSR here?
> > 
> > 
> > So that we have the right MMIO's in case we want to probe the HW with no
> > sink support. I wasn't what would happen if we reg_read() on PSR
> > registers without the correct MMIO base.
> 
> But isn't the goal of CAN_PSR to avoid any extra calls on platforms
> that either doesn't have support nor the panel? In this case we should
> never being touching any register.

We should not be writing to any PSR related registers if PSR cannot be
enabled. But I also think reading any hardware register should be
decoupled from a feature's enablement status. 


> > 
> > > 
> > > >  	/* Per platform default: all disabled. */
> > > >  	if (i915_modparams.enable_psr == -1)
> > > >  		i915_modparams.enable_psr = 0;
> > > > -- 
> > > > 2.11.0
> > > >