ACK: [SRU][Bionic][PATCH 0/2] HDMI/DP audio can't work on the laptop of Dell Latitude 5495

[Kai-Heng Feng]

> On 2018Jul20, at 14:41, Hui Wang <hui.wang at canonical.com> wrote:
> 
> BugLink: https://bugs.launchpad.net/bugs/1782689
> 
> 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.
> 
> 
> Jim Qu (2):
>  ALSA: hda: use PCI_BASE_CLASS_DISPLAY to replace PCI_CLASS_DISPLAY_VGA
>  vga_switcheroo: set audio client id according to bound GPU id
> 
> drivers/gpu/vga/vga_switcheroo.c | 62 +++++++++++++++++++++++++++++++++-------
> include/linux/vga_switcheroo.h   |  8 +++---
> sound/pci/hda/hda_intel.c        | 13 +++++----
> 3 files changed, 62 insertions(+), 21 deletions(-)

Acked-by: Kai-Heng Feng <kai.heng.feng at canonical.com>

> 
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> 2.7.4
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