Re: [Intel-gfx] [PATCH v4 13/14] drm/i915/tc: Call TypeC port flush_work/cleanup without modeset locks held

[Imre Deak <imre.deak@intel.com>]

On Wed, May 10, 2023 at 05:03:17PM +0300, Ville Syrjälä wrote:
> On Wed, May 10, 2023 at 01:31:30PM +0300, Imre Deak wrote:
> > Call the TypeC port flush_work and cleanup handlers without the modeset
> > locks held. These don't require the locks, as the work takes - as it
> > should be able to at any point in time - any locks it needs and by the
> > time cleanup is called and after cleanup returns the encoder is not in
> > use.
> > 
> > This is required by the next patch canceling a TypeC port work
> > synchronously during encoder suspend and shutdown, where the work can
> > take modeset locks as well, hence the canceling must be done without
> > holding the locks.
> > 
> > I also considered moving the modeset locking down to each encoder
> > suspend()/shutdown() hook instead, however locking the full modeset
> > state for each encoder separately would be odd, and the bigger change -
> > affecting all encoders - is beyond the scope of this patchset.
> 
> Hmm. What is it in the encoder shutdown/suspend hooks that
> actually needs the modeset locks?

In the case of intel_dp_encoder_suspend() for instance, I assume
nothing, since the VDD work and intel_pps_vdd_off_sync() should take
whatever locks they require.

So presumably most (all) of those could be made lockless. However, I
would like to leave that kind of change for a follow-up if possible, not
to affect in this patchset any other encoder types (again because of
possible need for CC stable).

> 
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c      | 27 +++++++++----------
> >  .../drm/i915/display/intel_display_types.h    | 12 +++++++++
> >  drivers/gpu/drm/i915/i915_driver.c            |  8 ++++++
> >  3 files changed, 33 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 813be957ed11b..7d09bd2412352 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -4617,31 +4617,27 @@ static bool intel_ddi_is_tc(struct drm_i915_private *i915, enum port port)
> >  
> >  static void intel_ddi_encoder_suspend(struct intel_encoder *encoder)
> >  {
> > -	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > -	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> > -	enum phy phy = intel_port_to_phy(i915, encoder->port);
> > -
> >  	intel_dp_encoder_suspend(encoder);
> > +}
> >  
> > -	if (!intel_phy_is_tc(i915, phy))
> > -		return;
> > +static void intel_ddi_tc_encoder_suspend_complete(struct intel_encoder *encoder)
> > +{
> > +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> >  
> >  	intel_tc_port_flush_work(dig_port);
> >  }
> >  
> >  static void intel_ddi_encoder_shutdown(struct intel_encoder *encoder)
> >  {
> > -	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > -	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> > -	enum phy phy = intel_port_to_phy(i915, encoder->port);
> > -
> >  	intel_dp_encoder_shutdown(encoder);
> >  	intel_hdmi_encoder_shutdown(encoder);
> > +}
> >  
> > -	if (!intel_phy_is_tc(i915, phy))
> > -		return;
> > +static void intel_ddi_tc_encoder_shutdown_complete(struct intel_encoder *encoder)
> > +{
> > +	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> >  
> >  	intel_tc_port_cleanup(dig_port);
> >  }
> > @@ -4908,6 +4904,9 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
> >  				    is_legacy ? "legacy" : "non-legacy");
> >  		}
> >  
> > +		encoder->suspend_complete = intel_ddi_tc_encoder_suspend_complete;
> > +		encoder->shutdown_complete = intel_ddi_tc_encoder_shutdown_complete;
> > +
> >  		if (intel_tc_port_init(dig_port, is_legacy) < 0)
> >  			goto err;
> >  	}
> > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> > index 270c4c84a2920..88b2a55d19f21 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > @@ -233,13 +233,25 @@ struct intel_encoder {
> >  	 * Called during system suspend after all pending requests for the
> >  	 * encoder are flushed (for example for DP AUX transactions) and
> >  	 * device interrupts are disabled.
> > +	 * All modeset locks are held while the hook is called.
> >  	 */
> >  	void (*suspend)(struct intel_encoder *);
> > +	/*
> > +	 * Called without the modeset locks held after the suspend() hook for
> > +	 * all encoders have been called.
> > +	 */
> > +	void (*suspend_complete)(struct intel_encoder *encoder);
> >  	/*
> >  	 * Called during system reboot/shutdown after all the
> >  	 * encoders have been disabled and suspended.
> > +	 * All modeset locks are held while the hook is called.
> >  	 */
> >  	void (*shutdown)(struct intel_encoder *encoder);
> > +	/*
> > +	 * Called without the modeset locks held after the shutdown() hook for
> > +	 * all encoders have been called.
> > +	 */
> > +	void (*shutdown_complete)(struct intel_encoder *encoder);
> >  	/*
> >  	 * Enable/disable the clock to the port.
> >  	 */
> > diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> > index fd198700272b1..705ba65f2ff9a 100644
> > --- a/drivers/gpu/drm/i915/i915_driver.c
> > +++ b/drivers/gpu/drm/i915/i915_driver.c
> > @@ -964,6 +964,10 @@ static void intel_suspend_encoders(struct drm_i915_private *dev_priv)
> >  		if (encoder->suspend)
> >  			encoder->suspend(encoder);
> >  	drm_modeset_unlock_all(&dev_priv->drm);
> > +
> > +	for_each_intel_encoder(&dev_priv->drm, encoder)
> > +		if (encoder->suspend_complete)
> > +			encoder->suspend_complete(encoder);
> >  }
> >  
> >  static void intel_shutdown_encoders(struct drm_i915_private *dev_priv)
> > @@ -978,6 +982,10 @@ static void intel_shutdown_encoders(struct drm_i915_private *dev_priv)
> >  		if (encoder->shutdown)
> >  			encoder->shutdown(encoder);
> >  	drm_modeset_unlock_all(&dev_priv->drm);
> > +
> > +	for_each_intel_encoder(&dev_priv->drm, encoder)
> > +		if (encoder->shutdown_complete)
> > +			encoder->shutdown_complete(encoder);
> >  }
> >  
> >  void i915_driver_shutdown(struct drm_i915_private *i915)
> > -- 
> > 2.37.2
> 
> -- 
> Ville Syrjälä
> Intel