drm/i915: ensure the force pipe A quirk is actually followed

Many BIOSen forget to turn on the pipe A after resume (because they
actually don't turn on anything), so we have to do that ourselves when
sanitizing the hw state.

I've discovered this due to the recent addition of a pipe WARN that
takes the force quirk into account.

v2: Actually try to enable the pipe with a proper configuration instead
of simpyl switching it on with whatever random state the bios left it
in after resume.

v3: Fixup rebase conflict - the load_detect functions have lost their
encoder argument.
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7602,6 +7602,33 @@ intel_connector_break_all_links(struct intel_connector *connector)
 	connector->encoder->base.crtc = NULL;
 }
 
+static void intel_enable_pipe_a(struct drm_device *dev)
+{
+	struct intel_connector *connector;
+	struct drm_connector *crt = NULL;
+	struct intel_load_detect_pipe load_detect_temp;
+
+	/* We can't just switch on the pipe A, we need to set things up with a
+	 * proper mode and output configuration. As a gross hack, enable pipe A
+	 * by enabling the load detect pipe once. */
+	list_for_each_entry(connector,
+			    &dev->mode_config.connector_list,
+			    base.head) {
+		if (connector->encoder->type == INTEL_OUTPUT_ANALOG) {
+			crt = &connector->base;
+			break;
+		}
+	}
+
+	if (!crt)
+		return;
+
+	if (intel_get_load_detect_pipe(crt, NULL, &load_detect_temp))
+		intel_release_load_detect_pipe(crt, &load_detect_temp);
+
+
+}
+
 static void intel_sanitize_crtc(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;
@@ -7650,6 +7677,15 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
 	}
 ok:
 
+	if (dev_priv->quirks & QUIRK_PIPEA_FORCE &&
+	    crtc->pipe == PIPE_A && !crtc->active) {
+		/* BIOS forgot to enable pipe A, this mostly happens after
+		 * resume. Force-enable the pipe to fix this, the update_dpms
+		 * call below we restore the pipe to the right state, but leave
+		 * the required bits on. */
+		intel_enable_pipe_a(dev);
+	}
+
 	/* Adjust the state of the output pipe according to whether we
 	 * have active connectors/encoders. */
 	intel_crtc_update_dpms(&crtc->base);