From: Bjorn Helgaas <helgaas@kernel.org>
To: Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc: tiwai@suse.com, linux-pci@vger.kernel.org,
alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound
Date: Tue, 27 Aug 2019 17:31:25 -0500 [thread overview]
Message-ID: <20190827223125.GB9987@google.com> (raw)
In-Reply-To: <20190827134756.10807-2-kai.heng.feng@canonical.com>
On Tue, Aug 27, 2019 at 09:47:56PM +0800, 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.
Just a terminology question:
I thought "using PCI port PM" meant using the PCI Power Management
Capability in config space to directly change the device's power
state, e.g., in pci_raw_set_power_state().
And I thought using _PS3, _PR3, etc would be part of "platform power
management"?
And AFAICT, _PR3 merely returns a list of power resources; it doesn't
disable power itself.
> 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@canonical.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);
> chip->driver_caps |= AZX_DCAPS_PM_RUNTIME;
> pci_dev_put(p);
> }
> --
> 2.17.1
>
next prev parent reply other threads:[~2019-08-27 22:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 13:47 [PATCH 1/2] PCI: Add a helper to check Power Resource Requirements _PR3 existence Kai-Heng Feng
2019-08-27 13:47 ` [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound Kai-Heng Feng
2019-08-27 14:50 ` Kai-Heng Feng
2019-08-27 15:24 ` Takashi Iwai
2019-08-27 22:31 ` Bjorn Helgaas [this message]
2019-08-28 8:25 ` Kai-Heng Feng
2019-08-28 18:01 ` [PATCH v2 " Kai-Heng Feng
2019-09-05 21:35 ` [alsa-devel] " Bjorn Helgaas
2019-09-17 9:36 ` Kai-Heng Feng
2019-09-18 12:42 ` [alsa-devel] [PATCH v3 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound to a driver Kai-Heng Feng
2019-08-27 15:25 ` [PATCH 1/2] PCI: Add a helper to check Power Resource Requirements _PR3 existence Takashi Iwai
2019-08-27 16:58 ` Kai-Heng Feng
2019-08-27 22:13 ` Bjorn Helgaas
2019-08-27 22:39 ` Peter Wu
2019-09-09 11:41 ` [alsa-devel] " Bjorn Helgaas
2019-09-20 11:23 ` Kai-Heng Feng
2019-09-20 13:26 ` Bjorn Helgaas
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