linux/Documentation/devicetree/bindings/arm/vexpress-sysreg.txt
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   1ARM Versatile Express system registers
   2--------------------------------------
   3
   4This is a system control registers block, providing multiple low level
   5platform functions like board detection and identification, software
   6interrupt generation, MMC and NOR Flash control etc.
   7
   8Required node properties:
   9- compatible value : = "arm,vexpress,sysreg";
  10- reg : physical base address and the size of the registers window
  11- gpio-controller : specifies that the node is a GPIO controller
  12- #gpio-cells : size of the GPIO specifier, should be 2:
  13  - first cell is the pseudo-GPIO line number:
  14    0 - MMC CARDIN
  15    1 - MMC WPROT
  16    2 - NOR FLASH WPn
  17  - second cell can take standard GPIO flags (currently ignored).
  18
  19Example:
  20        v2m_sysreg: sysreg@10000000 {
  21                compatible = "arm,vexpress-sysreg";
  22                reg = <0x10000000 0x1000>;
  23                gpio-controller;
  24                #gpio-cells = <2>;
  25        };
  26
  27This block also can also act a bridge to the platform's configuration
  28bus via "system control" interface, addressing devices with site number,
  29position in the board stack, config controller, function and device
  30numbers - see motherboard's TRM for more details.
  31
  32The node describing a config device must refer to the sysreg node via
  33"arm,vexpress,config-bridge" phandle (can be also defined in the node's
  34parent) and relies on the board topology properties - see main vexpress
  35node documentation for more details. It must must also define the
  36following property:
  37- arm,vexpress-sysreg,func : must contain two cells:
  38  - first cell defines function number (eg. 1 for clock generator,
  39    2 for voltage regulators etc.)
  40  - device number (eg. osc 0, osc 1 etc.)
  41
  42Example:
  43        mcc {
  44                arm,vexpress,config-bridge = <&v2m_sysreg>;
  45
  46                osc@0 {
  47                        compatible = "arm,vexpress-osc";
  48                        arm,vexpress-sysreg,func = <1 0>;
  49                };
  50        };
  51