drm/amd/display: Add debugfs to repress HPD and HPR_RX IRQs

[Why]
For debugging reasons it can be beneficial to disable any hotplug and DP shortpulse interrupt handling.

[How]
Expose a debugfs to set a flag to bypass HPD IRQ handling and skip IRQ handling if flag is set.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Bindu Ramamurthy <bindur12@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2552,11 +2552,14 @@ static void handle_hpd_irq(void *param)
 	struct drm_connector *connector = &aconnector->base;
 	struct drm_device *dev = connector->dev;
 	enum dc_connection_type new_connection_type = dc_connection_none;
-#ifdef CONFIG_DRM_AMD_DC_HDCP
 	struct amdgpu_device *adev = drm_to_adev(dev);
+#ifdef CONFIG_DRM_AMD_DC_HDCP
 	struct dm_connector_state *dm_con_state = to_dm_connector_state(connector->state);
 #endif
 
+	if (adev->dm.disable_hpd_irq)
+		return;
+
 	/*
 	 * In case of failure or MST no need to update connector status or notify the OS
 	 * since (for MST case) MST does this in its own context.
@@ -2696,6 +2699,10 @@ static void handle_hpd_rx_irq(void *param)
 
 	memset(&hpd_irq_data, 0, sizeof(hpd_irq_data));
 
+	if (adev->dm.disable_hpd_irq)
+		return;
+
+
 	/*
 	 * TODO:Temporary add mutex to protect hpd interrupt not have a gpio
 	 * conflict, after implement i2c helper, this mutex should be

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Advanced Micro Devices, Inc.
+ * Copyright (C) 2015-2020 Advanced Micro Devices, Inc. All rights reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -410,6 +410,7 @@ struct amdgpu_display_manager {
 	 */
 	struct amdgpu_encoder mst_encoders[AMDGPU_DM_MAX_CRTC];
 	bool force_timing_sync;
+	bool disable_hpd_irq;
 	bool dmcub_trace_event_en;
 	/**
 	 * @da_list:

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -3077,6 +3077,37 @@ static int force_timing_sync_get(void *data, u64 *val)
 DEFINE_DEBUGFS_ATTRIBUTE(force_timing_sync_ops, force_timing_sync_get,
 			 force_timing_sync_set, "%llu\n");
 
+
+/*
+ * Disables all HPD and HPD RX interrupt handling in the
+ * driver when set to 1. Default is 0.
+ */
+static int disable_hpd_set(void *data, u64 val)
+{
+	struct amdgpu_device *adev = data;
+
+	adev->dm.disable_hpd_irq = (bool)val;
+
+	return 0;
+}
+
+
+/*
+ * Returns 1 if HPD and HPRX interrupt handling is disabled,
+ * 0 otherwise.
+ */
+static int disable_hpd_get(void *data, u64 *val)
+{
+	struct amdgpu_device *adev = data;
+
+	*val = adev->dm.disable_hpd_irq;
+
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(disable_hpd_ops, disable_hpd_get,
+			 disable_hpd_set, "%llu\n");
+
 /*
  * Sets the DC visual confirm debug option from the given string.
  * Example usage: echo 1 > /sys/kernel/debug/dri/0/amdgpu_visual_confirm
@@ -3213,4 +3244,8 @@ void dtn_debugfs_init(struct amdgpu_device *adev)
 
 	debugfs_create_file_unsafe("amdgpu_dm_dcc_en", 0644, root, adev,
 				   &dcc_en_bits_fops);
+
+	debugfs_create_file_unsafe("amdgpu_dm_disable_hpd", 0644, root, adev,
+				   &disable_hpd_ops);
+
 }