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    SubjectRe: [PATCH] usb: xhci: add support for performing fake doorbell
    On Sat, Oct 01, 2016 at 11:58:10PM +0200, Rafał Miłecki wrote:
    > From: Rafał Miłecki <rafal@milecki.pl>
    >
    > Broadcom's Northstar XHCI controllers seem to need a special start
    > procedure to work correctly. There isn't any official documentation on
    > this, the problem is that controller doesn't detect any connected
    > devices with default setup. Moreover connecting USB device to controller
    > that doesn't run properly can cause SoC's watchdog issues.
    >
    > A workaround that was successfully tested on multiple devices is to
    > perform a fake doorbell. This patch adds code for doing that and a DT
    > binding enabling it.
    >
    > Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
    > ---
    > Documentation/devicetree/bindings/usb/usb-xhci.txt | 2 +
    > drivers/usb/host/xhci-plat.c | 6 +++
    > drivers/usb/host/xhci.c | 63 ++++++++++++++++++++--
    > drivers/usb/host/xhci.h | 1 +
    > 4 files changed, 69 insertions(+), 3 deletions(-)
    >
    > diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
    > index 966885c..ce01b7f 100644
    > --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
    > +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
    > @@ -26,6 +26,8 @@ Required properties:
    > Optional properties:
    > - clocks: reference to a clock
    > - usb3-lpm-capable: determines if platform is USB3 LPM capable
    > + - usb3-fake-doorbell: determines if controller requires a fake doorbell when
    > + starting it

    You should use Northstar XHCI compatible string to enable this. Then the
    DT doesn't need updating.

    Rob

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