linux-kernel - Re: [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound

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Date:   Tue, 27 Aug 2019 17:24:45 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     <bhelgaas@...gle.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound

On Tue, 27 Aug 2019 15:47:56 +0200,
Kai-Heng Feng wrote:
> 
> It's a common practice to let dGPU unbound and use PCI port PM to
> disable its power through _PR3. When the dGPU comes with an HDA
> function, the HDA won't be suspended if the dGPU is unbound, so the dGPU
> power can't be disabled.
> 
> Commit 37a3a98ef601 ("ALSA: hda - Enable runtime PM only for
> discrete GPU") only allows HDA to be runtime-suspended once GPU is
> bound, to keep APU's HDA working.
> 
> However, HDA on dGPU isn't that useful if dGPU is unbound. So let relax
> the runtime suspend requirement for dGPU's HDA function, to save lots of
> power.
> 
> BugLink: https://bugs.launchpad.net/bugs/1840835
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>  sound/pci/hda/hda_intel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> index 99fc0917339b..d4ee070e1a29 100644
> --- a/sound/pci/hda/hda_intel.c
> +++ b/sound/pci/hda/hda_intel.c
> @@ -1285,7 +1285,8 @@ static void init_vga_switcheroo(struct azx *chip)
>  		dev_info(chip->card->dev,
>  			 "Handle vga_switcheroo audio client\n");
>  		hda->use_vga_switcheroo = 1;
> -		hda->need_eld_notify_link = 1; /* cleared in gpu_bound op */
> +		/* cleared in gpu_bound op */
> +		hda->need_eld_notify_link = !pci_pr3_present(p);

Oh, right now I have a fix patch to submit for turning on the runtime
PM behavior upon the audio component registration, essentially for
amdgpu and nouveau.  My fix includes the movement of this flag into
hda_bus object, so this patch would become inapplicable (although it's
trivial).

So I can apply this patch with the correction to sound git tree if the
first patch gets ack from PCI maintainers (and they agree to apply
over sound git tree).

In anyway, I'm going to post my patch that will conflict with this.


thanks,

Takashi