On 9/11/26 10:32 PM, Romain Beauxis wrote:
Neither bootm nor EFI ExitBootServices() stops USB controllers
explicitly. Both only remove devices whose driver sets
DM_FLAG_ACTIVE_DMA or DM_FLAG_OS_PREPARE. xhci-dwc3 sets neither, so a
controller brought up by "usb start", e.g. from preboot for a USB
keyboard, is handed to the OS still running.
Set DM_FLAG_OS_PREPARE so that xhci_dwc3_remove() runs at handoff. This
is the path "usb stop" already takes: the xHCI is reset, its PHYs are
shut down and its clocks and resets are released. Child devices such as
hubs, storage and keyboards are removed first, and a controller already
stopped by "usb stop" is skipped. xhci-pci has done the same since
commit e3bbc1f74e05 ("usb: xhci-pci: Add DM_FLAG_OS_PREPARE flag"), as
have ohci-da8xx and the cdns3 wrappers.
On Apple silicon machines the running controller is user visible: Linux
does not enumerate a USB device attached to a Type-C port at boot until
it is unplugged and plugged back in.
boot/bootm.c bootm_final() does call dm_remove_devices_active() , is
that not sufficient to tear the controllers down before booting Linux ?
