Re: [Intel-gfx] [PATCH v3] drm/i915/psr: Force PSR probe only after full initialization

["Mun, Gwan-gyeong" <gwan-gyeong.mun@intel.com>]

On Thu, 2020-02-20 at 12:55 -0800, Souza, Jose wrote:
> On Thu, 2020-02-20 at 12:39 +0000, Mun, Gwan-gyeong wrote:
> > On Tue, 2020-02-18 at 12:39 -0800, José Roberto de Souza wrote:
> > > Commit 60c6a14b489b ("drm/i915/display: Force the state compute
> > > phase
> > > once to enable PSR") was forcing the state compute too earlier
> > > causing errors because not everything was initialized, so here
> > > moving to i915_driver_register() when everything is ready and
> > > driver
> > > is registering into the rest of the system.
> > > 
> > > Also fixing the place where it disarm the force probe as during
> > > the
> > > atomic check phase errors could happen like the ones due locking
> > > and
> > > it would cause PSR to never be enabled if that happens.
> > > Leaving the disarm to the atomic commit phase, intel_psr_enable()
> > > or
> > > intel_psr_update() will be called even if the current state do
> > > not
> > > allow PSR to be enabled.
> > > 
> > > v2: Check if intel_dp is null in
> > > intel_psr_force_mode_changed_set()
> > > v3: Check intel_dp before get dev_priv
> > > 
> > > Fixes: 60c6a14b489b ("drm/i915/display: Force the state compute
> > > phase
> > > once to enable PSR")
> > > Closes: https://gitlab.freedesktop.org/drm/intel/issues/1151
> > > Tested-by: Ross Zwisler <zwisler@google.com>
> > > Reported-by: Ross Zwisler <zwisler@google.com>
> > > Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_psr.c | 22
> > > ++++++++++++++++++++--
> > >  drivers/gpu/drm/i915/display/intel_psr.h |  1 +
> > >  drivers/gpu/drm/i915/i915_drv.c          |  3 +++
> > >  drivers/gpu/drm/i915/i915_drv.h          |  2 +-
> > >  4 files changed, 25 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > > b/drivers/gpu/drm/i915/display/intel_psr.c
> > > index b4942b6445ae..2a0f7354fba5 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > > @@ -936,6 +936,8 @@ void intel_psr_enable(struct intel_dp
> > > *intel_dp,
> > >  {
> > >  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> > >  
> > > +	intel_psr_force_mode_changed_set(intel_dp, false);
> > > +
> > Hi,
> > intel_psr_enable() and intel_psr_update already have checking
> > routine
> > for CAN_PSR and has_psr.
> > therefore we don't need to check twice here.
> 
> Minor overhead but if you really want I can remove the function call
> and just do a dev_priv->psr.force_mode_changed = false; for 
> intel_psr_enable/update
> 
> > And if there are no issues that moving "disarming
> > force_mode_changed"
> > to intel_psr_compute_config(), 
> > can we move them to intel_psr_compute_config()?
> 
> atomic check can fail at any point so we could disarm the
> mode_changed,
> fail, retry(because the return was EAGAIN) and then PSR will not be
> enabled.
> 
If disarming the "force_mode_changed" would be handled on
intel_psr_compute_config(),
(after failing atomic check and)the retry step will set "crtc_state-
>mode_changed = true" on 
intel_digital_connector_atomic_check(). ( because the
force_mode_changed is not disabled yet.)

The mode_changed will lead "encoder->compute_config" which will call
intel_psr_compute_config().
And we can disable "force_mode_changed" on intel_psr_compute_config()
which sets "crtc_state->has_psr = true".
the "crtc_state->has_psr" enables PSR.

> > >  	if (!crtc_state->has_psr)
> > >  		return;
> > >  
> > > @@ -1096,6 +1098,8 @@ void intel_psr_update(struct intel_dp
> > > *intel_dp,
> > >  	struct i915_psr *psr = &dev_priv->psr;
> > >  	bool enable, psr2_enable;
> > >  
> > > +	intel_psr_force_mode_changed_set(intel_dp, false);
> > > +
> > >  	if (!CAN_PSR(dev_priv) || READ_ONCE(psr->dp) != intel_dp)
> > >  		return;
> > >  
> > > @@ -1629,7 +1633,7 @@ void intel_psr_atomic_check(struct
> > > drm_connector *connector,
> > >  	struct drm_crtc_state *crtc_state;
> > >  
> > >  	if (!CAN_PSR(dev_priv) || !new_state->crtc ||
> > > -	    dev_priv->psr.initially_probed)
> > > +	    !dev_priv->psr.force_mode_changed)
> > >  		return;
> > >  
> > >  	intel_connector = to_intel_connector(connector);
> > > @@ -1640,5 +1644,19 @@ void intel_psr_atomic_check(struct
> > > drm_connector *connector,
> > >  	crtc_state = drm_atomic_get_new_crtc_state(new_state->state,
> > >  						   new_state->crtc);
> > >  	crtc_state->mode_changed = true;
> > > -	dev_priv->psr.initially_probed = true;
> > > +}
> > > +
> > > +void intel_psr_force_mode_changed_set(struct intel_dp *intel_dp,
> > > bool set)
> > IMHO, it would be better intel_psr_set_force_mode_changed() as a
> > function name.
> 
> Okay
> 
> > > +{
> > > +	struct drm_i915_private *dev_priv;
> > > +
> > > +	if (!intel_dp)
> > > +		return;
> > > +
> > > +	dev_priv = dp_to_i915(intel_dp);
> > > +	if (!CAN_PSR(dev_priv) || !intel_dp_is_edp(intel_dp) ||
> > > +	    intel_dp != dev_priv->psr.dp)
> > > +		return;
> > > +
> > > +	dev_priv->psr.force_mode_changed = set;
> > >  }
> > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.h
> > > b/drivers/gpu/drm/i915/display/intel_psr.h
> > > index c58a1d438808..27a70468e2b9 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_psr.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_psr.h
> > > @@ -40,5 +40,6 @@ bool intel_psr_enabled(struct intel_dp
> > > *intel_dp);
> > >  void intel_psr_atomic_check(struct drm_connector *connector,
> > >  			    struct drm_connector_state *old_state,
> > >  			    struct drm_connector_state *new_state);
> > > +void intel_psr_force_mode_changed_set(struct intel_dp *intel_dp,
> > > bool set);
> > >  
> > >  #endif /* __INTEL_PSR_H__ */
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c
> > > b/drivers/gpu/drm/i915/i915_drv.c
> > > index f7a1c33697b7..83791c197611 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -58,6 +58,7 @@
> > >  #include "display/intel_hotplug.h"
> > >  #include "display/intel_overlay.h"
> > >  #include "display/intel_pipe_crc.h"
> > > +#include "display/intel_psr.h"
> > >  #include "display/intel_sprite.h"
> > >  #include "display/intel_vga.h"
> > >  
> > > @@ -1256,6 +1257,8 @@ static void i915_driver_register(struct
> > > drm_i915_private *dev_priv)
> > >  
> > >  	intel_audio_init(dev_priv);
> > >  
> > > +	intel_psr_force_mode_changed_set(dev_priv->psr.dp, true);
> > > +
> > >  	/*
> > >  	 * Some ports require correctly set-up hpd registers for
> > > detection to
> > >  	 * work properly (leading to ghost connected connector status),
> > > e.g. VGA
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > > b/drivers/gpu/drm/i915/i915_drv.h
> > > index 3330b538d379..a546655072bd 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -505,7 +505,7 @@ struct i915_psr {
> > >  	bool dc3co_enabled;
> > >  	u32 dc3co_exit_delay;
> > >  	struct delayed_work dc3co_work;
> > > -	bool initially_probed;
> > > +	bool force_mode_changed;
> > >  };
> > >  
> > >  #define QUIRK_LVDS_SSC_DISABLE (1<<1)
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