Re: [PATCH v3] drm/i915: Break encoder->crtc link separately in intel_sanitize_crtc()

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 25 Apr 2014, Egbert Eich <eich@suse.de> wrote:
> Depending on the SDVO output_flags SDVO may have multiple connectors
> linking to the same encoder (in intel_connector->encoder->base).
> Only one of those connectors should be active (ie link to the encoder
> thru drm_connector->encoder).
> If intel_connector_break_all_links() is called from intel_sanitize_crtc()
> we may break the crtc connection of an encoder thru an inactive connector
> in which case intel_connector_break_all_links() will not be called again
> for the active connector if this happens to come later in the list due to:
>     if (connector->encoder->base.crtc != &crtc->base)
>                                  continue;
> in intel_sanitize_crtc().
> This will however leave the drm_connector->encoder linkage for this
> active connector in place. Subsequently this will cause multiple
> warnings in intel_connector_check_state() to trigger and the driver
> will eventually die in drm_encoder_crtc_ok() (because of crtc == NULL).
>
> To avoid this remove intel_connector_break_all_links() and move its
> code to its two calling functions: intel_sanitize_crtc() and
> intel_sanitize_encoder().
> This allows to implement the link breaking more flexibly matching
> the surrounding code: ie. in intel_sanitize_crtc() we can break the
> crtc link separatly after the links to the encoders have been
> broken which avoids above problem.
>
> This regression has been introduced in:
>
> commit 24929352481f085c5f85d4d4cbc919ddf106d381
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Mon Jul 2 20:28:59 2012 +0200
>
>     drm/i915: read out the modeset hw state at load and resume time
>
> so goes back to the very beginning of the modeset rework.
>
> Signed-off-by: Egbert Eich <eich@suse.de>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: stable@vger.kernel.org
> Cc: Jani Nikula <jani.nikula@linux.intel.com>

Pushed to -fixes, thanks for the patch and review.

BR,
Jani.


>
> v2: This patch takes care of the concernes voiced by Chris Wilson
> and Daniel Vetter that only breaking links if the drm_connector
> is linked to an encoder may miss some links.
> v3: move all encoder handling to encoder loop as suggested by
> Daniel Vetter.
> ---
>  drivers/gpu/drm/i915/intel_display.c | 26 ++++++++++++++------------
>  1 file changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b57210c..7ba8bf5 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11373,15 +11373,6 @@ void intel_modeset_init(struct drm_device *dev)
>  	}
>  }
>  
> -static void
> -intel_connector_break_all_links(struct intel_connector *connector)
> -{
> -	connector->base.dpms = DRM_MODE_DPMS_OFF;
> -	connector->base.encoder = NULL;
> -	connector->encoder->connectors_active = false;
> -	connector->encoder->base.crtc = NULL;
> -}
> -
>  static void intel_enable_pipe_a(struct drm_device *dev)
>  {
>  	struct intel_connector *connector;
> @@ -11463,8 +11454,17 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
>  			if (connector->encoder->base.crtc != &crtc->base)
>  				continue;
>  
> -			intel_connector_break_all_links(connector);
> +			connector->base.dpms = DRM_MODE_DPMS_OFF;
> +			connector->base.encoder = NULL;
>  		}
> +		/* multiple connectors may have the same encoder:
> +		 *  handle them and break crtc link separately */
> +		list_for_each_entry(connector, &dev->mode_config.connector_list,
> +				    base.head)
> +			if (connector->encoder->base.crtc == &crtc->base) {
> +				connector->encoder->base.crtc = NULL;
> +				connector->encoder->connectors_active = false;
> +			}
>  
>  		WARN_ON(crtc->active);
>  		crtc->base.enabled = false;
> @@ -11546,6 +11546,8 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
>  				      drm_get_encoder_name(&encoder->base));
>  			encoder->disable(encoder);
>  		}
> +		encoder->base.crtc = NULL;
> +		encoder->connectors_active = false;
>  
>  		/* Inconsistent output/port/pipe state happens presumably due to
>  		 * a bug in one of the get_hw_state functions. Or someplace else
> @@ -11556,8 +11558,8 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
>  				    base.head) {
>  			if (connector->encoder != encoder)
>  				continue;
> -
> -			intel_connector_break_all_links(connector);
> +			connector->base.dpms = DRM_MODE_DPMS_OFF;
> +			connector->base.encoder = NULL;
>  		}
>  	}
>  	/* Enabled encoders without active connectors will be fixed in
> -- 
> 1.8.4.5
>

-- 
Jani Nikula, Intel Open Source Technology Center