** Also affects: linux-oem (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Also affects: linux-oem (Ubuntu Bionic)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1782689
Title:
HDMI/DP audio can't work on the laptop of Dell Latitude 5495
Status in HWE Next:
New
Status in linux package in Ubuntu:
Incomplete
Status in linux-oem package in Ubuntu:
New
Status in linux source package in Bionic:
New
Status in linux-oem source package in Bionic:
New
Bug description:
This bug comes from the OEM project, and the engineer Jim Qu from AMD took
almost 2 weeks to investigate this problem, then he worte these two patches to
fix this problem and now the patches are merged to sound repository.
According to Jim Qu's investigation, the root cause of this problem is:
1. there is two GPU on the system. iGPU has a audio codec for HDMI output,
and dGPU is without audio codec it is only for offload rendering.
2. under runtime pm, when dGPU suspend, amdgpu will also call vgaswitchroo
driver to power off audio which vgaswitchroo client is VGA_SWITCHEROO_DIS.
3. In current HDA audio driver, the iGPU's audio will register to vgaswitchroo
as VGA_SWITCHEROO_DIS, therefore, the audio will be selected and powered
off
by runtime pm.
[Impact]
On the Dell Latitude 5495, If we plug a monitor with audio capability to the
HDMI/DP ports, we can't find HDMI/DP audio sinks as expected, then we can't
play any sound through HDMI/DP audio.
[Fix]
With these two patches, the driver will not always set vgaswicheroo clients of
HDA audio as VGA_SWITCHEROO_DIS, it will set it to _DIS or _IGD with the help
of callback function of DRM drivers. So on this machine, the vgaswicheroo
client
will be set _IGD, then it will not be powered off when discrete gpu is
powered off.
[Test Case]
We tested plug/unplug detection and playback through HDMI/DP audio,
everything works
well.
[Regression Potential]
Very low, without these two patches, the vgaswitchroo client of audio will be
set to _DIS unconditionally, it did not expose any problem because in the
past,
all the HDMI/DP audio codecs are in the discreate GPU. But on Latitude 5495,
the
HDMI/DP audio codec is in the integrated GPU, so we need to change the driver
to
let DRM driver decide if it is _DIS or _IGD, it will not introduce regression
for
old mahcines on old machines, the client will be set to _DIS as before.
And we have tested these two patches on some old machines with two gpus like
A+A
, I+A and I+N, all of them worked well as before.
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