From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas 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 Message-ID: <20190827223125.GB9987@google.com> References: <20190827134756.10807-1-kai.heng.feng@canonical.com> <20190827134756.10807-2-kai.heng.feng@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190827134756.10807-2-kai.heng.feng@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: Kai-Heng Feng Cc: tiwai@suse.com, linux-pci@vger.kernel.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org List-Id: alsa-devel@alsa-project.org 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 > --- > 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 >