• Ye Li's avatar
    usb: ehci-hcd: Add IAA handshake for removing async QH · e1769da1
    Ye Li authored
    According to EHCI spec, software needs to do handshake with HC for
    safely removing QH from async list. This handshake is implemented by
    setting IAAD (Interrupt on Async Advance Doorbell) bit in USB_USBCMD
    register and poll the IAA (Interrupt on Async Advance bit) in the
    USB_USBSTS to ensure the HC has released all on-chip state that may
    potentially reference one of the data structures just removed.
    
    Current codes only check active status of the last QTD, but this can't
    ensure the QH is released from HC. We can meet unrecoverable
    "EHCI timed out on TD" errors when running UEFI SCT tests on USB disk.
    The USB_ASYNCLISTADDR register is changed to a invalid address when the
    issue happens. It is fixed after adding the IAA handshake.
    
    Steps to reproduce the issue:
    1. Build the UEFI SCT from https://github.com/tianocore/edk2-test
    2. Build the EDK2 UEFI Shell from https://github.com/tianocore/edk2
    3. Copy SCT files and Shell.efi to USB disk FAT partition
    4. Lo...
    e1769da1
ehci.h 10.4 KB