From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kai-Heng Feng Subject: Re: [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound Date: Wed, 28 Aug 2019 16:25:08 +0800 Message-ID: <66C43B81-0A08-437F-B099-1C757A42E912@canonical.com> References: <20190827134756.10807-1-kai.heng.feng@canonical.com> <20190827134756.10807-2-kai.heng.feng@canonical.com> <20190827223125.GB9987@google.com> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Content-Type: text/plain; charset=utf-8; delsp=yes; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190827223125.GB9987@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Bjorn Helgaas 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 Hi Bjorn, at 06:31, Bjorn Helgaas wrote: > 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(). What I meant is to use pcieport.ko directly. > > And I thought using _PS3, _PR3, etc would be part of "platform power > management”? Ok, will update the wording. > > And AFAICT, _PR3 merely returns a list of power resources; it doesn't > disable power itself. Yes, through its _PS3 and _OFF. I’ll update the wording. Kai-Heng > >> 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