Re: [PATCH] drm/i915: Handle changing enable_psr parameter at runtime better

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

On Thu, 2018-03-08 at 08:07 +0100, Maarten Lankhorst wrote:
> Op 07-03-18 om 23:22 schreef Pandiyan, Dhinakaran:
> > On Wed, 2018-03-07 at 17:39 +0100, Maarten Lankhorst wrote:
> >> Similar to enable_fbc, enable_psr was ignored at runtime if it was
> >> changed. The easiest fix is to pretend enable_psr is ignored at
> >> configure time, and never activate it for !enable_psr, so both cases
> >> are handled without modesets.
> > What about cases where psr_flush() is not called and consequently the
> > module parameter is not checked? With HW tracking, PSR is
> > enabled/disabled during modeset and the hardware is expected to exit and
> > activate PSR without driver intervention.
> It looks like intel_frontbuffer_flush always calls intel_psr_flush,
> so we at least get a PSR toggle after every atomic commit?

I have a patch to remove flush() from legacy_cursor_update(). We end up
with an inconsistent behavior when that patch gets merged,
cursor moves -> trigger psr exit but don't read module parameter
commits -> trigger psr exit but read module parameter

Eventually, when we get to removing flush() from commits, then this
patch won't really be useful. And tests disabling/enabling PSR at
runtime will probably fail.


> 
> ~Maarten
> 
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >> Tested-by: Benjamin Berg <bberg@redhat.com>
> >> Cc: Benjamin Berg <bberg@redhat.com>
> >> ---
> >>  drivers/gpu/drm/i915/intel_psr.c | 19 ++++++++++---------
> >>  1 file changed, 10 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> >> index 23175c5c4a50..ac3ce7a1c2a7 100644
> >> --- a/drivers/gpu/drm/i915/intel_psr.c
> >> +++ b/drivers/gpu/drm/i915/intel_psr.c
> >> @@ -502,11 +502,6 @@ void intel_psr_compute_config(struct intel_dp *intel_dp,
> >>  	if (!CAN_PSR(dev_priv))
> >>  		return;
> >>  
> >> -	if (!i915_modparams.enable_psr) {
> >> -		DRM_DEBUG_KMS("PSR disable by flag\n");
> >> -		return;
> >> -	}
> >> -
> >>  	/*
> >>  	 * HSW spec explicitly says PSR is tied to port A.
> >>  	 * BDW+ platforms with DDI implementation of PSR have different
> >> @@ -559,7 +554,10 @@ void intel_psr_compute_config(struct intel_dp *intel_dp,
> >>  
> >>  	crtc_state->has_psr = true;
> >>  	crtc_state->has_psr2 = intel_psr2_config_valid(intel_dp, crtc_state);
> >> -	DRM_DEBUG_KMS("Enabling PSR%s\n", crtc_state->has_psr2 ? "2" : "");
> >> +	if (i915_modparams.enable_psr)
> >> +		DRM_DEBUG_KMS("Enabling PSR%s\n", crtc_state->has_psr2 ? "2" : "");
> >> +	else
> >> +		DRM_DEBUG_KMS("PSR disable by flag\n");
> >>  }
> >>  
> >>  static void intel_psr_activate(struct intel_dp *intel_dp)
> >> @@ -652,7 +650,9 @@ void intel_psr_enable(struct intel_dp *intel_dp,
> >>  	dev_priv->psr.enable_source(intel_dp, crtc_state);
> >>  	dev_priv->psr.enabled = intel_dp;
> >>  
> >> -	if (INTEL_GEN(dev_priv) >= 9) {
> >> +	if (!i915_modparams.enable_psr) {
> >> +		DRM_DEBUG_KMS("PSR disable by flag\n");
> >> +	} else if (INTEL_GEN(dev_priv) >= 9) {
> >>  		intel_psr_activate(intel_dp);
> >>  	} else {
> >>  		/*
> >> @@ -843,7 +843,7 @@ static void intel_psr_work(struct work_struct *work)
> >>  	 * recheck. Since psr_flush first clears this and then reschedules we
> >>  	 * won't ever miss a flush when bailing out here.
> >>  	 */
> >> -	if (dev_priv->psr.busy_frontbuffer_bits)
> >> +	if (dev_priv->psr.busy_frontbuffer_bits || !i915_modparams.enable_psr)
> >>  		goto unlock;
> >>  
> >>  	intel_psr_activate(intel_dp);
> >> @@ -1015,7 +1015,8 @@ void intel_psr_flush(struct drm_i915_private *dev_priv,
> >>  		return;
> >>  
> >>  	mutex_lock(&dev_priv->psr.lock);
> >> -	if (!dev_priv->psr.enabled) {
> >> +	if (!dev_priv->psr.enabled || !i915_modparams.enable_psr) {
> >> +		intel_psr_exit(dev_priv);
> >>  		mutex_unlock(&dev_priv->psr.lock);
> >>  		return;
> >>  	}
> 
> 
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