Re: [Intel-gfx] [PATCH 01/13] drm/i915/mst: Use .compute_config_late() to compute master transcoder

["Souza, Jose" <jose.souza@intel.com>]

This will not work for MST, here a example

Previous state:
MST master pipe A
MST slave pipe B

New state:
Pipe A being disabled

On drm_atomic_helper_check_modeset() both intel_crtc_states will be
added to the state with crtc_state->uapi.mode_changed=true.
Then on the regular for_each_oldnew_intel_crtc_in_state() loop config
of CRTC B will have mst_master_transcoder=INVALID_TRANSCODER that
differs from TRANSCODER_A and will keep mode_changed set.
Then on the config_late loop it will skip the interation on the
needs_modeset() check keeping CRTC B with
mst_master_transcoder=INVALID_TRANSCODER.

That would be caugh by CI if this tests were merged and the TGL machine
with MST is still on: https://patchwork.freedesktop.org/series/72211/

On Fri, 2020-03-13 at 18:48 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Use the recently introduced encoder .compute_config_late() hook to
> do the MST master transcoder assignment. Avoids having to do it
> in a funny way before we know the CPU transcoder of each pipe.
> 
> And now we can also properly use hw.active instead of uapi.active
> since it too has been calculated earlier for everyone.
> 
> Cc: José Roberto de Souza <jose.souza@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 98 +++++++++++------
> ----
>  1 file changed, 51 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 44f3fd251ca1..b9afc1135b9b 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -88,56 +88,10 @@ static int
> intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
>  	return 0;
>  }
>  
> -/*
> - * Iterate over all connectors and return the smallest transcoder in
> the MST
> - * stream
> - */
> -static enum transcoder
> -intel_dp_mst_master_trans_compute(struct intel_atomic_state *state,
> -				  struct intel_dp *mst_port)
> -{
> -	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> -	struct intel_digital_connector_state *conn_state;
> -	struct intel_connector *connector;
> -	enum pipe ret = I915_MAX_PIPES;
> -	int i;
> -
> -	if (INTEL_GEN(dev_priv) < 12)
> -		return INVALID_TRANSCODER;
> -
> -	for_each_new_intel_connector_in_state(state, connector,
> conn_state, i) {
> -		struct intel_crtc_state *crtc_state;
> -		struct intel_crtc *crtc;
> -
> -		if (connector->mst_port != mst_port || !conn_state-
> >base.crtc)
> -			continue;
> -
> -		crtc = to_intel_crtc(conn_state->base.crtc);
> -		crtc_state = intel_atomic_get_new_crtc_state(state,
> crtc);
> -		if (!crtc_state->uapi.active)
> -			continue;
> -
> -		/*
> -		 * Using crtc->pipe because crtc_state->cpu_transcoder
> is
> -		 * computed, so others CRTCs could have non-computed
> -		 * cpu_transcoder
> -		 */
> -		if (crtc->pipe < ret)
> -			ret = crtc->pipe;
> -	}
> -
> -	if (ret == I915_MAX_PIPES)
> -		return INVALID_TRANSCODER;
> -
> -	/* Simple cast works because TGL don't have a eDP transcoder */
> -	return (enum transcoder)ret;
> -}
> -
>  static int intel_dp_mst_compute_config(struct intel_encoder
> *encoder,
>  				       struct intel_crtc_state
> *pipe_config,
>  				       struct drm_connector_state
> *conn_state)
>  {
> -	struct intel_atomic_state *state =
> to_intel_atomic_state(conn_state->state);
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(encoder);
>  	struct intel_dp *intel_dp = &intel_mst->primary->dp;
> @@ -201,7 +155,56 @@ static int intel_dp_mst_compute_config(struct
> intel_encoder *encoder,
>  
>  	intel_ddi_compute_min_voltage_level(dev_priv, pipe_config);
>  
> -	pipe_config->mst_master_transcoder =
> intel_dp_mst_master_trans_compute(state, intel_dp);
> +	return 0;
> +}
> +
> +/*
> + * Iterate over all connectors and return a mask of
> + * all CPU transcoders streaming over the same DP link.
> + */
> +static unsigned int
> +intel_dp_mst_transcoder_mask(struct intel_atomic_state *state,
> +			     struct intel_dp *mst_port)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> +	const struct intel_digital_connector_state *conn_state;
> +	struct intel_connector *connector;
> +	u8 transcoders = 0;
> +	int i;
> +
> +	if (INTEL_GEN(dev_priv) < 12)
> +		return 0;
> +
> +	for_each_new_intel_connector_in_state(state, connector,
> conn_state, i) {
> +		const struct intel_crtc_state *crtc_state;
> +		struct intel_crtc *crtc;
> +
> +		if (connector->mst_port != mst_port || !conn_state-
> >base.crtc)
> +			continue;
> +
> +		crtc = to_intel_crtc(conn_state->base.crtc);
> +		crtc_state = intel_atomic_get_new_crtc_state(state,
> crtc);
> +
> +		if (!crtc_state->hw.active)
> +			continue;
> +
> +		transcoders |= BIT(crtc_state->cpu_transcoder);
> +	}
> +
> +	return transcoders;
> +}
> +
> +static int intel_dp_mst_compute_config_late(struct intel_encoder
> *encoder,
> +					    struct intel_crtc_state
> *crtc_state,
> +					    struct drm_connector_state
> *conn_state)
> +{
> +	struct intel_atomic_state *state =
> to_intel_atomic_state(conn_state->state);
> +	struct intel_dp_mst_encoder *intel_mst = enc_to_mst(encoder);
> +	struct intel_dp *intel_dp = &intel_mst->primary->dp;
> +
> +	/* lowest numbered transcoder will be designated master */
> +	crtc_state->mst_master_transcoder =
> +		ffs(intel_dp_mst_transcoder_mask(state, intel_dp)) - 1;
>  
>  	return 0;
>  }
> @@ -786,6 +789,7 @@ intel_dp_create_fake_mst_encoder(struct
> intel_digital_port *intel_dig_port, enum
>  	intel_encoder->pipe_mask = ~0;
>  
>  	intel_encoder->compute_config = intel_dp_mst_compute_config;
> +	intel_encoder->compute_config_late =
> intel_dp_mst_compute_config_late;
>  	intel_encoder->disable = intel_mst_disable_dp;
>  	intel_encoder->post_disable = intel_mst_post_disable_dp;
>  	intel_encoder->pre_pll_enable = intel_mst_pre_pll_enable_dp;
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