On Mon, 14 Mar 2016 16:30:22 +0100,
Lin, Mengdong wrote:
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai@suse.de]
> > Sent: Monday, March 14, 2016 9:03 PM
> > To: Yang, Libin
> > Cc: kernel test robot; lkp@01.org; LKML; Wu, Fengguang; Lin, Mengdong
> > Subject: Re: [lkp] [ALSA] ca53fbf3a6: WARNING: CPU: 0 PID: 151 at
> > sound/hda/hdac_i915.c:129 pin2port+0x2a/0x40 [snd_hda_core]()
> > 
> > On Mon, 14 Mar 2016 13:02:39 +0100,
> > Yang, Libin wrote:
> > >
> > > Hi Takashi,
> > >
> > > > -----Original Message-----
> > > > From: Takashi Iwai [mailto:tiwai@suse.de]
> > > > Sent: Monday, March 14, 2016 3:23 PM
> > > > To: kernel test robot
> > > > Cc: lkp@01.org; LKML; Wu, Fengguang; Yang, Libin; Lin, Mengdong
> > > > Subject: Re: [lkp] [ALSA] ca53fbf3a6: WARNING: CPU: 0 PID: 151 at
> > > > sound/hda/hdac_i915.c:129 pin2port+0x2a/0x40 [snd_hda_core]()
> > > >
> > > > On Mon, 14 Mar 2016 01:50:45 +0100,
> > > > kernel test robot wrote:
> > > > >
> > > > > FYI, we noticed the below changes on
> > > > >
> > > > > https://github.com/0day-ci/linux
> > > > > Takashi-Iwai/ALSA-hda-Add-a-sanity-
> > > > check-of-pin-port-mapping-on-i915-HDMI-DP/20160310-225740
> > > > > commit ca53fbf3a609b6831222078af9ddbecbf76fddce ("ALSA: hda -
> > > > Add a sanity check of pin / port mapping on i915 HDMI/DP")
> > > > >
> > > > >
> > > > > [   14.546058] snd_hda_intel 0000:00:1b.0: bound 0000:00:02.0
> > (ops
> > > > i915_audio_component_bind_ops [i915])
> > > > > [   14.549740] fbcon: inteldrmfb (fb0) is primary device
> > > > > [   14.553691] ------------[ cut here ]------------
> > > > > [   14.553707] WARNING: CPU: 0 PID: 151 at
> > > > sound/hda/hdac_i915.c:129 pin2port+0x2a/0x40 [snd_hda_core]()
> > > >
> > > > Does your tree contain the commit
> > > >   2f791908a70e95768596f5bb9e6de4f441d7bf13
> > > >       drm/i915: Fix bogus dig_port_map[] assignment for pre-HSW ?
> > > >
> > > > The commit above should cover it even for HSW.
> > > >
> > > > If it's already included, then it's really a bug, and the warning is
> > > > exactly for catching such a bug.  The HD-audio driver expects that
> > > > the valid audio ports are only from port B to port D while i915
> > > > driver assigns a different one.  I suspect that the current
> > > > assumption is too naive and broken for SKL and later in this regard.
> > > >
> > > > Libin, Mengdong, could you check whether the audio port mapping rule
> > > > is still valid?  At least, a wrong port-A mapping could be
> > > > reproduced even on a HSW laptop with DP-MST dock when I boot
> > without
> > > > eDP (e.g. video=eDP-1:d option).
> > >
> > > We checked with HW before, and the mapping should be right.
> > > What's the problem now? I will check with our HW and gfx team.
> > 
> > One problem I've heard is that port-A is reported from i915 ELD notifier.
> > This happens when you disable eDP and use DP-MST on a HSW machine.
> > Then port A DDI is also used for the DP-MST, and when it's plugged, it passes
> > port=0 to the notifier.
> 
> Hi Takashi,
> 
> Could you or someone provide the output of intel_audio_dump when the error happens?
> This can help us to check the pipe:port connections in GPU from the display register values.
> 
> For Haswell and later platforms, port A (DDI A) is only used for eDP, not for DP or HDMI. So I feel the DP-MST dock should not bridge port A to external monitors and so port A should not be reported by the ELD notifier.
> Maybe the port mapping has bug since i915 support for DP MST is still ongoing. 

Below are four outputs with 4.5-final kernel:

Normal boot
* intel-audio-laptop-normal	DP monitor connected to built-in DP port
* intel-audio-dock-normal	DP monitor connected to dock DP port

Boot with video=eDP-1:d option
* intel-audio-laptop-noedp	DP monitor connected to built-in DP port
* intel-audio-dock-noedp	DP monitor connected to dock DP port

I didn't check whether *this* kernel really caused the issue.  But, at
least, the last case (intel-audio-dock-noedp) triggered eld notifier
with port=0 in the past with 4.5-rc7.


HTH,

Takashi