usb: usb5303: add support for reference clock specified in device tree

USB3503 chip supports 8 values of reference clock. The value is
specified by REF_SEL[1:0] pins and INT_N line. This patch add support
for getting 'refclk' clock, enabling it and setting INT_N line according
to the value of the gathered clock. If no clock has been specified,
driver defaults to the old behaviour (assuming that clock has been
specified by REF_SEL pins from primary reference clock frequencies
table).

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/usb/usb3503.txt b/Documentation/devicetree/bindings/usb/usb3503.txt
index a018da4a7ad7..221ac0dbc678 100644
--- a/Documentation/devicetree/bindings/usb/usb3503.txt
+++ b/Documentation/devicetree/bindings/usb/usb3503.txt
@@ -15,6 +15,14 @@ Optional properties:
 - reset-gpios: Should specify GPIO for reset.
 - initial-mode: Should specify initial mode.
                 (1 for HUB mode, 2 for STANDBY mode)
+- refclk: Clock used for driving REFCLK signal (optional, if not provided
+        the driver assumes that clock signal is always available, its
+        rate is specified by REF_SEL pins and a value from the primary
+        reference clock frequencies table is used)
+- refclk-frequency: Frequency of the REFCLK signal as defined by REF_SEL
+        pins (optional, if not provided, driver will not set rate of the
+        REFCLK signal and assume that a value from the primary reference
+        clock frequencies table is used)
 
 Examples:
         usb3503@08 {