disp: msm: dp: add support for Trusted UI transitions

We add support for Trusted UI (TUI) transitions and address the
following use cases:

1. Display was active before TUI start
    - Power off on TUI start, power off on TUI stop
    - Register access not allowed after TUI start (skip all
      events except disconnect)
2. Hotplug while TUI is active
    - Connect: skip sending connect uevent
    - Disconnect: send disconnect uevent and skip any controller
      programming
3. TUI start while processing HPD High
    - Complete all connect work (and therefore any register access)
      then send connect uevent
4. Audio
    - Disable audio at TUI start and skip audio programming if TUI
      is active

Change-Id: I553e5fa9f3b8265dd0410bf2d616a9accf90605f
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>

msm/dp/dp_audio.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
- * Copyright (c) 2016-2019, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2016-2020, The Linux Foundation. All rights reserved.
  */
 
 #ifndef _DP_AUDIO_H_
@@ -15,15 +15,18 @@
  * struct dp_audio
  * @lane_count: number of lanes configured in current session
  * @bw_code: link rate's bandwidth code for current session
+ * @tui_active: set to true if TUI is active in the system
  */
 struct dp_audio {
 	u32 lane_count;
 	u32 bw_code;
+	bool tui_active;
 
 	/**
 	 * on()
 	 *
-	 * Enables the audio by notifying the user module.
+	 * Notifies user mode clients that DP is powered on, and that audio
+	 * playback can start on the external display.
 	 *
 	 * @dp_audio: an instance of struct dp_audio.
 	 *
@@ -34,7 +37,8 @@ struct dp_audio {
 	/**
 	 * off()
 	 *
-	 * Disables the audio by notifying the user module.
+	 * Notifies user mode clients that DP is shutting down, and audio
+	 * playback should be stopped on the external display.
 	 *
 	 * @dp_audio: an instance of struct dp_audio.
 	 *