Dear Hui, Takashi,
Op 14-04-2020 om 13:35 schreef Hui Wang:
On 2020/4/14 下午6:27, Takashi Iwai wrote:
On Tue, 14 Apr 2020 12:14:05 +0200,
Hui Wang wrote:
Before the pci_driver->probe() is called, the pci subsystem calls
runtime_forbib() and runtime_get_sync() on this pci dev, so only call
runtime_put_autosuspend() is not enough to enable the runtime_pm on
this device.
For controllers with vgaswitcheroo feature, the pci/quirks.c will call
runtime_allow() for this dev, then the controllers could enter
rt_idle/suspend/resume, but for non-vgaswitcheroo controllers like
Intel hda controllers, the runtime_pm is not enabled even it calls
put_autosuspend(). Need to call runtime_allow() for those controllers
in the hda driver.
From what I can tell there are no ill effects of calling
runtime_allow() twice. Technically, the check against
use_vga_switcheroo() is thus redundant.
Is there a good reason why runtime_allow() is called in the pci quirks
rather than in hda_intel? Is it a suggestion to perform this call in
hda_intel regardless of whether it's a switcheroo-device or not, and
removing calls to runtime_allow() from the PCI quirks?
Thanks. Best,
Roy
Signed-off-by: Hui Wang <hui.wang@xxxxxxxxxxxxx>
Was this behavior changed from the earlier kernels? I thought this
was left untouched because it's supposed to be set via udev rules or
such.
Oh, I don't know that, according to my test with ubuntu rootfs, the
runtime pm is not enabled on Intel's hda controllers. But with the sof
driver, the controller driver calls runtime_allow()
(soc/sof/sof-pci-dev.c), so I sent this patch.
Regards,
Hui.
OTOH, enabling the runtime PM is almost mandatory for modern systems,
and I'm fine to apply this kind of forcible enablement.
thanks,
Takashi
---
sound/pci/hda/hda_intel.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 8519051a426e..779705bef88b 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2356,6 +2356,8 @@ static int azx_probe_continue(struct azx *chip)
if (azx_has_pm_runtime(chip)) {
pm_runtime_use_autosuspend(&pci->dev);
+ if (!use_vga_switcheroo(chip))
+ pm_runtime_allow(&pci->dev);
pm_runtime_put_autosuspend(&pci->dev);
}
--
2.17.1
