On Mon, May 2, 2022 at 4:39 AM Hector Martin <marcan@xxxxxxxxx> wrote: > > WiFi and SD card devices on M1 Macs have a separate power enable GPIO. > Add support for this to the PCIe controller. This is modeled after how > pcie-fu740 does it. It did, but it's not ideal really. The problem is the GPIO is really associated with the device (WiFi/SD) rather than the PCI host and therefore should be part of a WiFi or SD node. You probably don't have one (yet), but I would suspect that SD will need one for all the standard MMC/SD DT properties. The secondary issue is we'll end up adding more power sequencing properties to control ordering and timing for different devices. The exception here is standard PCI slot properties like perst#, clkreq, and standard voltage rails can go in the host bridge (and for new bindings, those should really be in the root port node). For a complicated example, see Hikey960 or 970. Of course with power control related properties there's a chicken or egg issue that the PCI device is not discoverable until the device is powered on. This issue comes up over and over with various hacky solutions in the bindings. The PCI subsystem needs to solve this. My suggestion is that if the firmware says there is a device on the bus and it wasn't probed, then we should force probing (or add a pre-probe hook for drivers). That is what MDIO bus does for example. Rob
