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

From: Kai-Heng Feng
Date: Tue Aug 27 2019 - 10:50:17 EST

at 21:47, Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> 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

Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>

Forgot to mention that for some platforms this issue happen after commit b516ea586d71 ("PCI: Enable NVIDIA HDA controllersâ) which starts to unhide the âhiddenâ HDA.


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)
"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;