On Fri, Mar 29, 2024 at 05:12:19PM +0900, Takashi Sakamoto wrote: > On Fri, Mar 29, 2024 at 05:41:16AM +0100, Lukas Wunner wrote: > > Just checked the ACPI tables and there's an FPEN method below the > > FRWR device which toggles GPIO 48 on the PCH. Checked the schematics > > as well and GPIO 48 is marked FW_PWR_EN. The GPIO controls load > > switches which cut power to the FW643 chip when nothing is connected. > > > > Also, FW_PWR_EN feeds into an SLG4AP016V chip where it seems to > > internally gate FW_CLKREQ_L. > > > > I'm guessing the driver may need to call the FPEN ACPI method after > > issuing a SBR to force the chip on (or perhaps first off, then on) > > and thereby re-enable Clock Request. > > > > It's a pity the ohci.c driver doesn't seem to support runtime PM. > > That would allow cutting power to the chip when nothing is connected > > and thus increase battery life. The ACPI tables indicate that the > > platform sends a notification when something is plugged in, so all > > the necessary ingredients are there but we're not taking advantage > > of them. > > Yup. In both PCI drivers and unit drivers belonging to Linux FireWire > subsystem, any type of runtime PM is not supported. If I integrate 1394 > OHCI driver, I should implement all of the above in any callback of > runtime PM, or the part of the above is already supported by any driver > in parent PCI layer? The power management method Apple uses to cut power to the FireWire controller, Thunderbolt controller and discrete GPU is nonstandard. It's *implemented* in ACPI, but doesn't *conform* to ACPI: There are no Power Resources described in the ACPI tables, just custom methods. This can be made to work on Linux by assigning a dev_pm_domain to the Root Port above the FireWire controller. The dev_pm_domain callbacks cut power to the FireWire controller on ->runtime_suspend() and reinstate it on ->runtime_resume(). The reason this needs to be done at the Root Port level is that the PCI core assumes the FireWire controller is powered on when it calls pci_pm_runtime_resume() for it. Normally that function would reinstate power through ACPI via pci_power_up(), but that doesn't work due to the nonstandard nature of Apple's ACPI tables. I've implemented this 8 years ago for Thunderbolt but unfortunately got sidetracked and thus haven't been able to finish upstreaming it yet: https://github.com/l1k/linux/commit/a53d44439d42 I'm not as familiar with ohci.c as I am (or was) with thunderbolt.ko. If you could amend ohci.c to call pm_runtime_get() when something is attached and call pm_runtime_put() when something is detached, I could look into bringing up the ACPI stuff. You could acquire one runtime PM ref for each attached device or just acquire a single ref if *anything* is connected at all. Doesn't matter. But acquiring one ref per attached device might be simpler. I would also need a function to perform a bus scan upon runtime resume which looks for new devices and acquires refs as necessary. Once that infrastructure exists, adding the Apple-specific ACPI stuff wouldn't be too hard for me to do as I could just adapt what I did for Thunderbolt. Thanks, Lukas
