dt-bindings: phy: add a document for MediaTek tphy

This adds a document for tphy which supports physical layer
functionality for a number of controllers on MediaTek SoCs,
such as, USB2.0, USB3.0, PCIe, and SATA.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>

diff --git a/doc/device-tree-bindings/phy/phy-mtk-tphy.txt b/doc/device-tree-bindings/phy/phy-mtk-tphy.txt
new file mode 100644 (file)
index 0000000..037c5a4
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+++ b/doc/device-tree-bindings/phy/phy-mtk-tphy.txt
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+MediaTek T-PHY binding
+--------------------------
+
+T-phy controller supports physical layer functionality for a number of
+controllers on MediaTek SoCs, such as, USB2.0, USB3.0, PCIe, and SATA.
+
+Required properties (controller (parent) node):
+ - compatible  : should be one of
+                 "mediatek,generic-tphy-v1"
+ - clocks      : (deprecated, use port's clocks instead) a list of phandle +
+                 clock-specifier pairs, one for each entry in clock-names
+ - clock-names : (deprecated, use port's one instead) must contain
+                 "u3phya_ref": for reference clock of usb3.0 analog phy.
+
+Required nodes : a sub-node is required for each port the controller
+                 provides. Address range information including the usual
+                 'reg' property is used inside these nodes to describe
+                 the controller's topology.
+
+Optional properties (controller (parent) node):
+ - reg         : offset and length of register shared by multiple ports,
+                 exclude port's private register.
+ - mediatek,src-ref-clk-mhz    : frequency of reference clock for slew rate
+                 calibrate
+ - mediatek,src-coef   : coefficient for slew rate calibrate, depends on
+                 SoC process
+
+Required properties (port (child) node):
+- reg          : address and length of the register set for the port.
+- clocks       : a list of phandle + clock-specifier pairs, one for each
+                 entry in clock-names
+- clock-names  : must contain
+                 "ref": 48M reference clock for HighSpeed analog phy; and 26M
+                       reference clock for SuperSpeed analog phy, sometimes is
+                       24M, 25M or 27M, depended on platform.
+- #phy-cells   : should be 1 (See second example)
+                 cell after port phandle is phy type from:
+                       - PHY_TYPE_USB2
+                       - PHY_TYPE_USB3
+                       - PHY_TYPE_PCIE
+                       - PHY_TYPE_SATA
+
+Example:
+
+       u3phy2: usb-phy@1a244000 {
+               compatible = "mediatek,generic-tphy-v1";
+               reg = <0x1a244000 0x0700>;
+               #address-cells = <1>;
+               #size-cells = <1>;
+               ranges;
+               status = "disabled";
+
+               u2port1: usb-phy@1a244800 {
+                       reg = <0x1a244800 0x0100>;
+                       clocks = <&topckgen CLK_TOP_USB_PHY48M>;
+                       clock-names = "ref";
+                       #phy-cells = <1>;
+                       status = "okay";
+               };
+
+               u3port1: usb-phy@1a244900 {
+                       reg = <0x1a244900 0x0700>;
+                       clocks = <&clk26m>;
+                       clock-names = "ref";
+                       #phy-cells = <1>;
+                       status = "okay";
+               };
+       };
+
+Specifying phy control of devices
+---------------------------------
+
+Device nodes should specify the configuration required in their "phys"
+property, containing a phandle to the phy port node and a device type;
+phy-names for each port are optional.
+
+Example:
+
+#include <dt-bindings/phy/phy.h>
+
+usb30: usb@11270000 {
+       ...
+       phys = <&u2port0 PHY_TYPE_USB2>, <&u3port0 PHY_TYPE_USB3>;
+       phy-names = "usb2-0", "usb3-0";
+       ...
+};