drm/vc4: hdmi: Introduce an output_enabled flag

We currently poke at encoder->crtc in the ALSA code path to determine
whether the HDMI output is enabled or not, and thus whether we should
allow the audio output.

However, that pointer is deprecated and shouldn't really be used by
atomic drivers anymore. Since we have the infrastructure in place now,
let's just create a flag that we toggle to report whether the controller
is currently enabled and use that instead of encoder->crtc in ALSA.

Link: https://lore.kernel.org/r/20211025141113.702757-9-maxime@cerno.tech
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -725,6 +725,11 @@ static void vc4_hdmi_encoder_post_crtc_powerdown(struct drm_encoder *encoder,
 
 static void vc4_hdmi_encoder_disable(struct drm_encoder *encoder)
 {
+	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
+
+	mutex_lock(&vc4_hdmi->mutex);
+	vc4_hdmi->output_enabled = false;
+	mutex_unlock(&vc4_hdmi->mutex);
 }
 
 static void vc4_hdmi_csc_setup(struct vc4_hdmi *vc4_hdmi, bool enable)
@@ -1218,6 +1223,11 @@ static void vc4_hdmi_encoder_post_crtc_enable(struct drm_encoder *encoder,
 
 static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
 {
+	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
+
+	mutex_lock(&vc4_hdmi->mutex);
+	vc4_hdmi->output_enabled = true;
+	mutex_unlock(&vc4_hdmi->mutex);
 }
 
 static void vc4_hdmi_encoder_atomic_mode_set(struct drm_encoder *encoder,
@@ -1397,14 +1407,12 @@ static inline struct vc4_hdmi *dai_to_hdmi(struct snd_soc_dai *dai)
 
 static bool vc4_hdmi_audio_can_stream(struct vc4_hdmi *vc4_hdmi)
 {
-	struct drm_encoder *encoder = &vc4_hdmi->encoder.base.base;
-
 	lockdep_assert_held(&vc4_hdmi->mutex);
 
 	/*
-	 * The encoder doesn't have a CRTC until the first modeset.
+	 * If the controller is disabled, prevent any ALSA output.
 	 */
-	if (!encoder->crtc)
+	if (!vc4_hdmi->output_enabled)
 		return false;
 
 	/*

drivers/gpu/drm/vc4/vc4_hdmi.h

@@ -203,6 +203,12 @@ struct vc4_hdmi {
 	 * for use by ALSA hooks and interrupt handlers. Protected by @mutex.
 	 */
 	struct drm_display_mode saved_adjusted_mode;
+
+	/**
+	 * @output_enabled: Is the HDMI controller currently active?
+	 * Protected by @mutex.
+	 */
+	bool output_enabled;
 };
 
 static inline struct vc4_hdmi *