• Alan Stern's avatar
    USB: hub: Add Kconfig option to reduce number of port initialization retries · fb6f076d
    Alan Stern authored
    Description based on one by Yasushi Asano:
    
    According to 6.7.22 A-UUT “Device No Response” for connection timeout
    of USB OTG and EH automated compliance plan v1.2, enumeration failure
    has to be detected within 30 seconds.  However, the old and new
    enumeration schemes each make a total of 12 attempts, and each attempt
    can take 5 seconds to time out, so the PET test fails.
    
    This patch adds a new Kconfig option (CONFIG_USB_FEW_INIT_RETRIES);
    when the option is set all the initialization retry loops except the
    outermost are reduced to a single iteration.  This reduces the total
    number of attempts to four, allowing Linux hosts to pass the PET test.
    
    The new option is disabled by default to preserve the existing
    behavior.  The reduced number of retries may fail to initialize a few
    devices that currently do work, but for the most part there should be
    no change.  And in cases where the initialization does fail, it will
    fail much more quickly.
    Reported-and-tested-by: default avataryasushi asano <yazzep@gmail.com>
    Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Link: https://lore.kernel.org/r/20200928152217.GB134701@rowland.harvard.eduSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    fb6f076d
hub.c 175 KB