Hi, On 3/4/21 4:34 PM, Alexander Monakov wrote: > Hello, Hans, Linux PM folks, > > I'm looking for clarification regarding this patch discussion: > > https://patchwork.kernel.org/project/linux-pm/patch/20180420101834.15783-2-0v3rdr0n3@xxxxxxxxx/ > > Hans said, > >> Ah, so the AHCI code has runtime pm enabled by default (so there >> is another pm_runtime_allow() somewhere, but then disables it for >> unused ports to make hotpluging something into those ports work. > > I have a laptop where two unused AHCI SATA controllers are present (but > obviously nothing can be hotplugged into them). Apparently due to the above, > they do not enter runtime autosuspend. > > The problem is, these "ATA port" nodes don't seem to participate in udev > hierarchy, so it's unclear how I'm supposed to automatically re-enable > runtime PM for them. For PCI device nodes, I have > > ACTION=="add", SUBSYSTEM=="pci", TEST=="power/control", ATTR{power/control}="auto" > > but ata1/uevent is empty, so there's no obvious way to write the corresponding > UDev rule. You can enable runtime-pm from udev using the following rule: ACTION=="add", SUBSYSTEM=="ata_port", ATTR{../../power/control}="auto" > Prior to discovering the above patch discussion, I have filed a bug: > https://bugzilla.kernel.org/show_bug.cgi?id=211837 > > Does the above correctly reflect how AHCI PM is supposed to be? This is a complicated question, I just checked and according to: https://www.intel.com/content/www/us/en/io/serial-ata/serial-ata-ahci-spec-rev1-3-1.html AHCI 1.3 compliant controllers should raise a PME signal on hotplug changes even when in D3. So perhaps the solution is to catch this signal and then wakeup the controller; and remove the pm_runtime_forbid(dev); call from ata_tport_add(). I don't have much experience with dealing with the PME stuff, so you will need to do some research there, or perhaps someone else can help? This seems to be more of a sata/ahci question then a generic linux-pm question though, so I have added Jebns and linux-ide to the To / Cc. > If so, what is > the proper way to enable runtime PM for unused ATA ports? Regards, Hans
