linux-kernel - [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 21:47:56 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     bhelgaas@...gle.com, tiwai@...e.com
Cc:     linux-pci@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        Kai-Heng Feng <kai.heng.feng@...onical.com>
Subject: [PATCH 2/2] ALSA: hda: Allow HDA to be runtime suspended when dGPU is not bound

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);
 		chip->driver_caps |= AZX_DCAPS_PM_RUNTIME;
 		pci_dev_put(p);
 	}
-- 
2.17.1