Re: [PATCH] drm/i915/psr: Kill delays when activating psr back.

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

On Wed, 2018-06-13 at 16:49 -0700, Dhinakaran Pandiyan wrote:
> On Wed, 2018-06-13 at 12:26 -0700, Rodrigo Vivi wrote:
> > 
> > The immediate enabling was actually not an issue for the
> > HW perspective for core platforms that have HW tracking.
> > HW will wait few identical idle frames before transitioning
> > to actual psr active anyways.
> > 
> > Now that we removed VLV/CHV out of the picture completely
> > we can safely remove any delays.
> > 
> > Note that this patch also remove the delayed activation
> > on HSW and BDW introduced by commit 'd0ac896a477d
> > ("drm/i915: Delay first PSR activation.")'. This was
> > introduced to fix a blank screen on VLV/CHV and also
> > masked some frozen screens on other core platforms.
> > Probably the same that we are now properly hunting and fixing.
> > 
> > v2:(DK): Remove unnecessary WARN_ONs and make some other
> >          VLV | CHV more readable.
> > v3: Do it regardless the timer rework.
> > v4: (DK/CI): Add VLV || CHV check on cancel work at psr_disable.
> > v5: Kill remaining items and fully rework activation functions.
> > v6: Rebase on top of VLV/CHV clean-up and keep the reactivation
> >     on a regular non-delayed work to avoid extra delays on exit
> >     calls and allow us to add few more safety checks before
> >     real activation.
> We have to implement this bspec step in the disable sequence now that
> you are removing the delay - 
> "Wait for SRD_STATUS to show SRD is Idle. This will take up to one
> full
> frame time (1/refresh rate), plus SRD exit training time (max of
> 6ms),
> plus SRD aux channel handshake (max of 1.5ms)."
> 
> Otherwise, we can end up re-enabling right after a disable in
> psr_exit()
> 
> 
> > 
> > 
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c |  2 --
> >  drivers/gpu/drm/i915/i915_drv.h     |  2 +-
> >  drivers/gpu/drm/i915/intel_psr.c    | 29 +++++++------------------
> > ----
> >  3 files changed, 8 insertions(+), 25 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
> > b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 769ab9745834..948b973af067 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -2660,8 +2660,6 @@ static int i915_edp_psr_status(struct
> > seq_file
> > *m, void *data)
> >  	seq_printf(m, "Enabled: %s\n", yesno((bool)dev_priv-
> > > 
> > > psr.enabled));
> >  	seq_printf(m, "Busy frontbuffer bits: 0x%03x\n",
> >  		   dev_priv->psr.busy_frontbuffer_bits);
> > -	seq_printf(m, "Re-enable work scheduled: %s\n",
> > -		   yesno(work_busy(&dev_priv->psr.work.work)));
> >  
> >  	if (dev_priv->psr.psr2_enabled)
> >  		enabled = I915_READ(EDP_PSR2_CTL) &
> > EDP_PSR2_ENABLE;
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index be8c2f0823c4..19defe73b156 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -613,7 +613,7 @@ struct i915_psr {
> >  	bool sink_support;
> >  	struct intel_dp *enabled;
> >  	bool active;
> > -	struct delayed_work work;
> > +	struct work_struct work;
> >  	unsigned busy_frontbuffer_bits;
> >  	bool sink_psr2_support;
> >  	bool link_standby;
> > diff --git a/drivers/gpu/drm/i915/intel_psr.c
> > b/drivers/gpu/drm/i915/intel_psr.c
> > index 71dfe541740f..ef0f4741a95d 100644
> > --- a/drivers/gpu/drm/i915/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > @@ -671,21 +671,7 @@ 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) {
> > -		intel_psr_activate(intel_dp);
> > -	} else {
> > -		/*
> > -		 * FIXME: Activation should happen immediately
> > since
> > this
> > -		 * function is just called after pipe is fully
> > trained and
> > -		 * enabled.
> > -		 * However on some platforms we face issues when
> > first
> > -		 * activation follows a modeset so quickly.
> > -		 *     - On HSW/BDW we get a recoverable frozen
> > screen until
> > -		 *       next exit-activate sequence.
> > -		 */
> > -		schedule_delayed_work(&dev_priv->psr.work,
> > -				      msecs_to_jiffies(intel_dp-
> > > 
> > > panel_power_cycle_delay * 5));
> > -	}
> > +	intel_psr_activate(intel_dp);
> >  
> >  unlock:
> >  	mutex_unlock(&dev_priv->psr.lock);
> > @@ -768,8 +754,6 @@ void intel_psr_disable(struct intel_dp
> > *intel_dp,
> >  
> >  	dev_priv->psr.enabled = NULL;
> >  	mutex_unlock(&dev_priv->psr.lock);
> > -
> > -	cancel_delayed_work_sync(&dev_priv->psr.work);
> >  }
> >  
> >  static bool psr_wait_for_idle(struct drm_i915_private *dev_priv)
> > @@ -805,10 +789,13 @@ static bool psr_wait_for_idle(struct
> > drm_i915_private *dev_priv)
> >  static void intel_psr_work(struct work_struct *work)
> >  {
> >  	struct drm_i915_private *dev_priv =
> > -		container_of(work, typeof(*dev_priv),
> > psr.work.work);
> > +		container_of(work, typeof(*dev_priv), psr.work);
> >  
> >  	mutex_lock(&dev_priv->psr.lock);
> >  
> > +	if (!dev_priv->psr.enabled)
> > +		goto unlock;
> > +
> I thought flush_work() was missing in psr_disable(), but this check
> should take care of not enabling PSR after psr_disable()
> 
Looks like a cancel_work_sync() is still needed,
https://bugs.freedesktop.org/show_bug.cgi?id=106948

If the work item was already scheduled and is followed by psr_disable
-> psr_enable, we'll end up hitting the psr.active warning.



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