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    SubjectRe: [PATCH 1/1] usb: core: lpm: set lpm_capable for root hub device
    On Fri, Jun 12, 2015 at 09:29:37AM +0800, Lu Baolu wrote:
    > Commit 25cd2882e2fc ("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 25cd2882e2fc ("usb/xhci: Change how we indicate
    > a host supports Link PM.").
    >
    > Cc: stable@vger.kernel.org # 3.15
    > Reported-by: Kevin Strasser <kevin.strasser@linux.intel.com>
    > Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
    > ---
    > drivers/usb/core/hcd.c | 6 ++++++
    > drivers/usb/core/hub.c | 2 +-
    > drivers/usb/core/usb.h | 1 +
    > 3 files changed, 8 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
    > index 45a915c..48b208d 100644
    > --- a/drivers/usb/core/hcd.c
    > +++ b/drivers/usb/core/hcd.c
    > @@ -1032,6 +1032,12 @@ static int register_root_hub(struct usb_hcd *hcd)
    > }
    > }
    >
    > + if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {

    Why are you treating a binary coded value as a hex number to compare
    against?



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