Re: [Intel-gfx] [PATCH v3 10/11] drm/i915/display: Check if pipe fastset is allowed by external dependencies

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Dec 16, 2019 at 02:07:41PM -0800, José Roberto de Souza wrote:
> Check if fastset is allowed by external dependencies like other pipes
> and transcoders.
> 
> Right now this patch only forces a fullmodeset in MST slaves of MST
> masters that needs a fullmodeset but it will be needed for port sync
> as well.
> 
> v3:
> - moved handling to intel_atomic_check() this way is guarantee that
> all pipes will have its state computed
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 63 ++++++++++++++++----
>  1 file changed, 50 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index f1c0687bf69b..2627a7bcb45c 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -13941,19 +13941,6 @@ static void intel_crtc_check_fastset(const struct intel_crtc_state *old_crtc_sta
>  
>  	new_crtc_state->uapi.mode_changed = false;
>  	new_crtc_state->update_pipe = true;
> -
> -	/*
> -	 * If we're not doing the full modeset we want to
> -	 * keep the current M/N values as they may be
> -	 * sufficiently different to the computed values
> -	 * to cause problems.
> -	 *
> -	 * FIXME: should really copy more fuzzy state here
> -	 */
> -	new_crtc_state->fdi_m_n = old_crtc_state->fdi_m_n;
> -	new_crtc_state->dp_m_n = old_crtc_state->dp_m_n;
> -	new_crtc_state->dp_m2_n2 = old_crtc_state->dp_m2_n2;
> -	new_crtc_state->has_drrs = old_crtc_state->has_drrs;
>  }
>  
>  static int intel_crtc_add_planes_to_state(struct intel_atomic_state *state,
> @@ -14121,6 +14108,56 @@ static int intel_atomic_check(struct drm_device *dev,
>  			any_ms = true;
>  	}
>  
> +	/**
> +	 * Check if fastset is allowed by external dependencies like other
> +	 * pipes and transcoders.
> +	 *
> +	 * Right now it only forces a fullmodeset when the MST master
> +	 * transcoder did not changed but the pipe of the master transcoder
> +	 * needs a fullmodeset so all slaves also needs to do a fullmodeset.
> +	 */
> +	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		struct intel_crtc_state *new_crtc_state_iter;
> +		struct intel_crtc *crtc_iter;
> +		int j;
> +
> +		if (!intel_dp_mst_is_slave_trans(new_crtc_state) ||
> +		    needs_modeset(new_crtc_state))

shouldn't this be
if (!mst_master || !needs_modeset)
	continue;
?

> +			continue;
> +
> +		for_each_new_intel_crtc_in_state(state, crtc_iter,
> +						 new_crtc_state_iter, j) {
> +			if (new_crtc_state->mst_master_transcoder !=
> +			    new_crtc_state_iter->cpu_transcoder)
> +				continue;
> +
> +			if (needs_modeset(new_crtc_state_iter)) {
> +				new_crtc_state->uapi.mode_changed = true;
> +				new_crtc_state->update_pipe = false;
> +			}
> +			break;

Hmm. So I guess the break here is because we're going to keep iterating
the outer loop anyway? Don't think that works with the s/slave/master/
fix above.

I suggest moving this inner loop into a separate function entirely.
Could simply pass in the master_transcoder to that function and then
we wouldn't even have this clash with variable names for the two
crtcs/crtc_states.

Somethig like (with better funciton names ofc :)

mst_modeset_slaves(state, master_transcoder)
{
	for_each() {
		if (master_transcoder == crtc_state->master_transcoder)
			modeset=1;
	}
}

atomic_check()
{
	for_each()
		compute();

	for_each() {
		if (master && needs_modeset()
			mst_modeset_slaves(state, crtc_state->cpu_transcoder);
	}

	for_each() {
		if (fastset)
			copy();
	}
}

Or do we also need to force a modeset for the master if a slave needs a
modeset? I'm trying to think if there's a way that we could end up with
a slave changing its master (thus needing modeset) without the master
being flagged for modeset...

> +		}
> +	}
> +
> +	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> +					    new_crtc_state, i) {
> +		if (needs_modeset(new_crtc_state))
> +			continue;
> +
> +		/*
> +		 * If we're not doing the full modeset we want to
> +		 * keep the current M/N values as they may be
> +		 * sufficiently different to the computed values
> +		 * to cause problems.
> +		 *
> +		 * FIXME: should really copy more fuzzy state here
> +		 */
> +		new_crtc_state->fdi_m_n = old_crtc_state->fdi_m_n;
> +		new_crtc_state->dp_m_n = old_crtc_state->dp_m_n;
> +		new_crtc_state->dp_m2_n2 = old_crtc_state->dp_m2_n2;
> +		new_crtc_state->has_drrs = old_crtc_state->has_drrs;

A separate function for this fastset state copy might also be nice so we
don't have to see these mundane details in this higher level code.

> +	}
> +
>  	if (any_ms && !check_digital_port_conflicts(state)) {
>  		DRM_DEBUG_KMS("rejecting conflicting digital port configuration\n");
>  		ret = EINVAL;
> -- 
> 2.24.1

-- 
Ville Syrjälä
Intel
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