Messages in this thread | | | Subject | Re: [alsa-devel] [PATCH v4 3/3] ALSA: hda: Disabled unused audio controller for Dell platforms with Switchable Graphics | From | Kai Heng Feng <> | Date | Thu, 26 Apr 2018 15:52:08 +0800 |
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> On Apr 25, 2018, at 5:13 AM, Lukas Wunner <lukas@wunner.de> wrote: > > On Mon, Apr 23, 2018 at 04:18:35PM +0800, Kai Heng Feng wrote: >>> On Apr 23, 2018, at 4:08 PM, Pali Rohár <pali.rohar@gmail.com> wrote: >>> On Monday 23 April 2018 16:04:55 Kai Heng Feng wrote: >>>>> On Apr 20, 2018, at 8:10 PM, Takashi Iwai <tiwai@suse.de> wrote: >>>>> On Fri, 20 Apr 2018 11:44:32 +0200, Kai-Heng Feng wrote: >>>>>> Now it's a typical discrete-only system. HDMI audio comes from AMD >>>>>> audio >>>>>> controller, others from Intel audio controller. >>>>>> >>>>>> When SG is enabled, the unused AMD audio contoller still exposes its >>>>>> sysfs, so userspace still opens the control file and stream. If >>>>>> userspace tries to output sound through the stream, it hangs the >>>>>> system. >>>>> >>>>> Hm, could you give more information about how it hangs? >>>> >>>> Well, I should say "it hangs the userspace process" instead. >>>> >>>> $ speaker-test -t wav -c 2 -D hw:CARD=HDMI,DEV=3 >>>> ...and it just stopped. Can't Ctrl+C to break it. >>> >>> So userspace process cannot be killed at all? Then it is different bug >>> in kernel and disabling pci device is just a workaround. Not a real fix. >>> >>> I would propose to find out what happen and why it cannot be killed >>> (probably it stuck somewhere in kernel) and fix it properly. >> >> That's because the audio device got runtime suspended by the graphics. >> >> In this case, if we really want to use the the discrete audio, then we >> also >> need to wake up the graphics. >> The discrete audio is totally useless when SG is enabled, so my approach >> is >> just to disable it. > > I don't quite follow, that should be fixed by commit 07f4f97d7b4b > ("vga_switcheroo: Use device link for HDA controller") which landed > in v4.17-rc1.
Looks like I hit a new bug: the discrete GFX and its audio controller never enters to D3. The GFX can enter to D3 with my prosed patch.
> > My understanding was that with SG enabled, the external DP/HDMI ports > are muxed to the Intel GPU, so audio can only be streamed to external > displays by the Intel HDA, not by the HDA integrated into the discrete > AMD/Nvidia GPU. Audio streamed to the latter would essentially end up > in a blackhole. And preventing the user from seeing such useless audio > devices was the sole purpose of this commit. Am I missing something?
Yes this is the intention.
Kai-Heng
> > Thanks, > > Lukas
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