On 19.11.2021 14:51, Takashi Iwai wrote:
On Thu, 18 Nov 2021 23:13:50 +0100, Heiner Kallweit wrote:
On 18.11.2021 22:28, Takashi Iwai wrote:
On Thu, 18 Nov 2021 21:33:34 +0100, Heiner Kallweit wrote:
I get the following warning caused by 4f66a9ef37d3 ("ALSA: hda: intel: More comprehensive PM runtime setup for controller driver"):
snd_hda_intel 0000:00:1f.3: Unbalanced pm_runtime_enable!
Not sure how this patch was tested because the warning is obvious. The patch doesn't consider what the PCI sub-system does with regard to RPM. Have a look at pci_pm_init().
I'd understand to add the call to pm_runtime_dont_use_autosuspend(), but for all other added calls I see no justification.
If being unsure about when to use which RPM call best involve linux-pm@vger.kernel.org.
Thanks for the notice. It's been through Intel CI and tests on a few local machines, maybe we haven't checked carefully those errors but only concentrated on the other issues, as it seems.
There were two problems: one was the runtime PM being kicked off even during the PCI driver remove call, and another was the proper runtime PM setup after re-binding.
Having a look at the commit message of "ALSA: hda: fix general protection fault in azx_runtime_idle" the following sounds weird:
- pci-driver.c:pm_runtime_put_sync() leads to a call to rpm_idle() which again calls azx_runtime_idle()
rpm_idle() is only called if usage_count is 1 when entering pm_runtime_put_sync. And this should not be the case. pm_runtime_get_sync() increments the usage counter before remove() is called, and remove() should also increment the usage counter. This doesn't seem to happen. Maybe for whatever reason pm_runtime_get_noresume() isn't called in azx_free(), or azx_free() isn't called from remove(). I think you should trace the call chain from the PCI core calling remove() to pm_runtime_get_noresume() getting called or not.
Neither of them, supposedly. Now I took a deeper look at the code around it and dug into the git log, and found that the likely problem was the recent PCI core code refactoring (removal of pci->driver, etc) that have been already reverted; that was why linux-next-20211109 was broken and linux-next-20211110 worked. With the leftover pci->driver, the stale runtime PM callback was called at the pm_runtime_put_sync() call in pci_device_remove().
I also noticed that partially I was on the wrong path.
In anyway, I'll drop the invalid calls of pm_runtime_enable() / disable() & co. Maybe keeping pm_runtime_forbid() and pm_runtime_dont_use_autosuspend() at remove still makes some sense as a counter-part for the probe calls, though.
The call to pm_runtime_forbid() in pci_pm_init() is a heritage from early ACPI times when broken ACPI implementations had problems with RPM. There's a discussion (w/o result yet) to enable RPM per default for newer ACPI versions.
Calling pm_runtime_forbid() in the driver removal path isn't strictly needed but it doesn't hurt.
thanks,
Takashi