drm/i915: dynamic Haswell display power well support

We can disable (almost) all the display hw if we only use pipe A, with
the integrated edp transcoder on port A. Because we don't set the cpu
transcoder that early (yet), we need to help us with a trick to simply
check for any edp encoders.

v2: Paulo Zanoni pointed out that we also need to configure the eDP
cpu transcoder correctly.

v3: Made by Paulo Zanoni
  - Rebase patch to be on top of "fix intel_init_power_wells" patch
  - Fix typos
  - Fix a small bug by adding a "connectors_active" check
  - Restore the initial code that unconditionally enables the power
    well when taking over from the BIOS

v4: Made by Paulo Zanoni
  - One more typo spotted by Jani Nikula

v5: Made by Paulo Zanoni
  - Rebase
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ddi.c

@@ -988,7 +988,13 @@ void intel_ddi_enable_pipe_func(struct drm_crtc *crtc)
 	if (cpu_transcoder == TRANSCODER_EDP) {
 		switch (pipe) {
 		case PIPE_A:
-			temp |= TRANS_DDI_EDP_INPUT_A_ONOFF;
+			/* Can only use the always-on power well for eDP when
+			 * not using the panel fitter, and when not using motion
+			  * blur mitigation (which we don't support). */
+			if (dev_priv->pch_pf_size)
+				temp |= TRANS_DDI_EDP_INPUT_A_ONOFF;
+			else
+				temp |= TRANS_DDI_EDP_INPUT_A_ON;
 			break;
 		case PIPE_B:
 			temp |= TRANS_DDI_EDP_INPUT_B_ONOFF;

drivers/gpu/drm/i915/intel_display.c

@@ -5607,6 +5607,35 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	return fdi_config_ok ? ret : -EINVAL;
 }
 
+static void haswell_modeset_global_resources(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool enable = false;
+	struct intel_crtc *crtc;
+	struct intel_encoder *encoder;
+
+	list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) {
+		if (crtc->pipe != PIPE_A && crtc->base.enabled)
+			enable = true;
+		/* XXX: Should check for edp transcoder here, but thanks to init
+		 * sequence that's not yet available. Just in case desktop eDP
+		 * on PORT D is possible on haswell, too. */
+	}
+
+	list_for_each_entry(encoder, &dev->mode_config.encoder_list,
+			    base.head) {
+		if (encoder->type != INTEL_OUTPUT_EDP &&
+		    encoder->connectors_active)
+			enable = true;
+	}
+
+	/* Even the eDP panel fitter is outside the always-on well. */
+	if (dev_priv->pch_pf_size)
+		enable = true;
+
+	intel_set_power_well(dev, enable);
+}
+
 static int haswell_crtc_mode_set(struct drm_crtc *crtc,
 				 struct drm_display_mode *mode,
 				 struct drm_display_mode *adjusted_mode,
@@ -8480,6 +8509,8 @@ static void intel_init_display(struct drm_device *dev)
 		} else if (IS_HASWELL(dev)) {
 			dev_priv->display.fdi_link_train = hsw_fdi_link_train;
 			dev_priv->display.write_eld = haswell_write_eld;
+			dev_priv->display.modeset_global_resources =
+				haswell_modeset_global_resources;
 		}
 	} else if (IS_G4X(dev)) {
 		dev_priv->display.write_eld = g4x_write_eld;