Documentation/devicetree/bindings/clock/renesas,rcar-usb2-clock-sel.txt

   1 * Renesas R-Car USB 2.0 clock selector
   2
   3 This file provides information on what the device node for the R-Car USB 2.0
   4 clock selector.
   5
   6 If you connect an external clock to the USB_EXTAL pin only, you should set
   7 the clock rate to "usb_extal" node only.
   8 If you connect an oscillator to both the USB_XTAL and USB_EXTAL, this module
   9 is not needed because this is default setting. (Of course, you can set the
  10 clock rates to both "usb_extal" and "usb_xtal" nodes.
  11
  12 Case 1: An external clock connects to R-Car SoC
  13         +----------+   +--- R-Car ---------------------+
  14         |External  |---|USB_EXTAL ---> all usb channels|
  15         |clock     |   |USB_XTAL                       |
  16         +----------+   +-------------------------------+
  17 In this case, we need this driver with "usb_extal" clock.
  18
  19 Case 2: An oscillator connects to R-Car SoC
  20         +----------+   +--- R-Car ---------------------+
  21         |Oscillator|---|USB_EXTAL -+-> all usb channels|
  22         |          |---|USB_XTAL --+                   |
  23         +----------+   +-------------------------------+
  24 In this case, we don't need this selector.
  25
  26 Required properties:
  27 - compatible: "renesas,r8a7795-rcar-usb2-clock-sel" if the device is a part of
  28               an R8A7795 SoC.
  29               "renesas,r8a7796-rcar-usb2-clock-sel" if the device if a part of
  30               an R8A7796 SoC.
  31               "renesas,rcar-gen3-usb2-clock-sel" for a generic R-Car Gen3
  32               compatible device.
  33
  34               When compatible with the generic version, nodes must list the
  35               SoC-specific version corresponding to the platform first
  36               followed by the generic version.
  37
  38 - reg: offset and length of the USB 2.0 clock selector register block.
  39 - clocks: A list of phandles and specifier pairs.
  40 - clock-names: Name of the clocks.
  41  - The functional clock must be "ehci_ohci"
  42  - The USB_EXTAL clock pin must be "usb_extal"
  43  - The USB_XTAL clock pin must be "usb_xtal"
  44 - #clock-cells: Must be 0
  45
  46 Example (R-Car H3):
  47
  48         usb2_clksel: clock-controller@e6590630 {
  49                 compatible = "renesas,r8a77950-rcar-usb2-clock-sel",
  50                              "renesas,rcar-gen3-usb2-clock-sel";
  51                 reg = <0 0xe6590630 0 0x02>;
  52                 clocks = <&cpg CPG_MOD 703>, <&usb_extal>, <&usb_xtal>;
  53                 clock-names = "ehci_ohci", "usb_extal", "usb_xtal";
  54                 #clock-cells = <0>;
  55         };