[Bug 109968] New: Audio not routing to external display Samsung 4K U28D590 when connected over USB type-c

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109968

            Bug ID: 109968
           Summary: Audio not routing to external display Samsung 4K
                    U28D590 when connected over USB type-c
           Product: DRI
           Version: DRI git
          Hardware: x86-64 (AMD64)
                OS: other
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: chintan.m.patel at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 143625
  --> https://bugs.freedesktop.org/attachment.cgi?id=143625&action=edit
Non working audio with Samsung 4K Series D model

Connecting Samsung Monitor 4K display(U28D590) to Chromebook (WHL), audio
doesn't route to display (same device and monitor works fine with HDMI ).
Connection type is USB Type-C to DP. Audio drivers are legacy HD Audio and
graphics is i915. 

Issue only happens with this particular monitor U28D590 and not happening on
Samsung 4K U28E590, Dell or any other monitor(as far as I know).

I have also read edid after connection and it shows "Audio Data Block"
evtest is also passes.

Issue is not reprodcible after adding 5 sec delay: 

diff --git a/drivers/gpu/drm/i915/intel_audio.c
b/drivers/gpu/drm/i915/intel_audio.c
index ee3ca2de983b..9c794968bb2a 100644
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -26,7 +26,7 @@
#include <drm/i915_component.h>
#include <drm/intel_lpe_audio.h>
#include "intel_drv.h"
-
+#include<linux/delay.h>
#include <drm/drmP.h>
#include <drm/drm_edid.h>
#include "i915_drv.h"
@@ -456,7 +456,8 @@ static void hsw_audio_codec_enable(struct intel_encoder
*encoder,
        const u8 *eld = connector->eld;
        u32 tmp;
        int len, i;
-
+       mdelay(5000);
        DRM_DEBUG_KMS("Enable audio codec on pipe %c, %u bytes ELD\n",
                      pipe_name(pipe), drm_eld_size(eld));

Important Observations:
1. Same monitor U28D590 works fine on Windows or any other chromebook.
2. Tried on different platforms with Legacy –HDA (no dsp), issue is
reproducible
3. If above mentioned delay is less than 5 sec, issue is reproducible.
4. Issue reproducible with drm-tip; 78b288a16a32 drm-tip:
2019y-03m-08d-19h-11m-52s UTC integration manifest

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