答复: [alsa-devel] ??????: [PATCH] vgaswitchroo: set audio client id according to bound gpu client id

[Takashi Iwai]

On Mon, 09 Jul 2018 18:03:48 +0200,
Alex Deucher wrote:
> 
> On Mon, Jul 9, 2018 at 11:57 AM, Takashi Iwai <tiwai at suse.de> wrote:
> > On Mon, 09 Jul 2018 17:53:19 +0200,
> > Qu, Jim wrote:
> >>
> >> Hi All,
> >>
> >> Here, I want to clarify the audio device is bound to iGPU. There is no audio codec for dGPU.
> >
> > I'm confused.  So you mean that the HDMI detection on Intel GPU
> > doesn't work with the hybrid GPUs?  And no audio codec on discrete
> > GPU...?  Why do we need vga_switcheroo at all, then?
> 
> The original problem is the audio codec is getting associated with
> dGPU rather than the iGPU so switcheroo tries to power down the audio
> codec when it powers down the dGPU.  We got a bit sidetracked in the
> discussion however.

Ah, thanks, that clarifies better, but still I'm lost about what's
going on...

Can anyone summarize the problem and the results with the recent (>=
4.17) Linux kernel...?


thanks,

Takashi


> Alex
> 
> >
> >
> > Takashi
> >
> >
> >>
> >> Thanks
> >> JimQu
> >>
> >> -----邮件原件-----
> >> 发件人: Lukas Wunner <lukas at wunner.de>
> >> 发送时间: 2018年7月9日 23:48
> >> 收件人: Takashi Iwai <tiwai at suse.de>
> >> 抄送: Alex Deucher <alexdeucher at gmail.com>; alsa-devel at alsa-project.org; amd-gfx at lists.freedesktop.org; Qu, Jim <Jim.Qu at amd.com>; dri-devel at lists.freedesktop.org; Deucher, Alexander <Alexander.Deucher at amd.com>
> >> 主题: Re: [alsa-devel] ??????: [PATCH] vgaswitchroo: set audio client id according to bound gpu client id
> >>
> >> On Mon, Jul 09, 2018 at 05:04:22PM +0200, Takashi Iwai wrote:
> >> > On Mon, 09 Jul 2018 15:58:51 +0200, Alex Deucher wrote:
> >> > > On Mon, Jul 9, 2018 at 6:16 AM, Qu, Jim <Jim.Qu at amd.com> wrote:
> >> > > > > You're saying above that the HDA controller isn't runtime
> >> > > > > resumed on hotplug of a display.  Is that necessary to retrieve ELD or something?
> >> > > > > I'm not sure if there's code in the HDA driver to acquire a
> >> > > > > runtime PM ref on HPD, but maybe it's necessary.  Or maybe the
> >> > > > > code is there but somehow no HPD interrupt is received by the HDA driver?
> >> > > >
> >> > > > So far, I do not find any code about audio response HPD in kernel.
> >> > > > the HPD interrupt will sent to user mode via uevent, not sure
> >> > > > whether audio user mode driver can receive the event or not.
> >> > >
> >> > > On the gfx side at least, we can get a hotplug event via ACPI
> >> > > (depending on the OEM design) if displays are attached/detached
> >> > > while the dGPU is powered down.  I suppose the gfx driver could call
> >> > > into the audio driver during one of those events.  On the gfx side
> >> > > at least we just generate the gfx hotplug event and let userspace deal with it.
> >> >
> >> > IMO, a more proper way would be to have the direct communication
> >> > between the graphics driver and the audio driver like i915 driver
> >> > does.  Then the audio driver can get plug/unplug event at more
> >> > accurate timing without races.
> >>
> >> Since v4.17, every time the GPU is powered up, the HDA controller is runtime resumed to PCI_D0.  (See the call to pci_wakeup_bus() in
> >> vga_switcheroo_runtime_resume() added by dcac86b7d0.)
> >>
> >> If the HDA controller can't detect presence of an HDMI display even if it's in PCI_D0, then I suppose that needs to be adressed in the HDA driver.  Thus so far I don't see the need to call from amdgpu into the HDA driver.
> >>
> >> Thanks,
> >>
> >> Lukas
>