• Lu Baolu's avatar
    usb: core: lpm: set lpm_capable for root hub device · 2d2a3167
    Lu Baolu authored
    Commit 25cd2882 ("usb/xhci: Change how we indicate a host supports
    Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed
    root hub. The intention of that change was to avoid touching usb core
    internal field, a.k.a. lpm_capable, and let usb core to set it by
    checking U1 and U2 exit latency values in the descriptor.
    
    Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately,
    root hub is a special usb device as it has no parent. Hub_port_init()
    will never be called for a root hub device. That means lpm_capable will
    by no means be set for the root hub. As the result, lpm isn't functional
    at all in Linux kernel.
    
    This patch add the code to check and set lpm_capable when registering a
    root hub device. It could be back-ported to kernels as old as v3.15,
    that contains the Commit 25cd2882 ("usb/xhci: Change how we indicate
    a host supports Link PM.").
    
    Cc: stable@vger.kernel.org # 3.15
    Reported-by: default avatarKevin Strasser <kevin.strasser@linux.intel.com>
    Signed-off-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
    Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    2d2a3167
hcd.c 84.5 KB