Re: [PATCH] usb: xhci: add support for performing fake doorbell

From: Rafa?? Mi??ecki <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: Rafa?? Mi??ecki <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