drm/i915/audio: add DOC comment describing HDA over HDMI/DP
v2: include the section in the drm docbook.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index f6a9d7b..01b8ca5 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3855,6 +3855,11 @@
</para>
</sect2>
<sect2>
+ <title>High Definition Audio</title>
+!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
+!Idrivers/gpu/drm/i915/intel_audio.c
+ </sect2>
+ <sect2>
<title>DPIO</title>
!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
<table id="dpiox2">
diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
index 9181b85d..44c49df 100644
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -28,6 +28,27 @@
#include "intel_drv.h"
#include "i915_drv.h"
+/**
+ * DOC: High Definition Audio over HDMI and Display Port
+ *
+ * The graphics and audio drivers together support High Definition Audio over
+ * HDMI and Display Port. The audio programming sequences are divided into audio
+ * codec and controller enable and disable sequences. The graphics driver
+ * handles the audio codec sequences, while the audio driver handles the audio
+ * controller sequences.
+ *
+ * The disable sequences must be performed before disabling the transcoder or
+ * port. The enable sequences may only be performed after enabling the
+ * transcoder and port, and after completed link training.
+ *
+ * The codec and controller sequences could be done either parallel or serial,
+ * but generally the ELDV/PD change in the codec sequence indicates to the audio
+ * driver that the controller sequence should start. Indeed, most of the
+ * co-operation between the graphics and audio drivers is handled via audio
+ * related registers. (The notable exception is the power management, not
+ * covered here.)
+ */
+
static const struct {
int clock;
u32 config;