The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)

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FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/i2c/i2c-ocores.txt

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    1 Device tree configuration for i2c-ocores
    2 
    3 Required properties:
    4 - compatible      : "opencores,i2c-ocores"
    5                     "aeroflexgaisler,i2cmst"
    6                     "sifive,fu540-c000-i2c", "sifive,i2c0"
    7                     For Opencore based I2C IP block reimplemented in
    8                     FU540-C000 SoC.
    9                     "sifive,fu740-c000-i2c", "sifive,i2c0"
   10                     For Opencore based I2C IP block reimplemented in
   11                     FU740-C000 SoC.
   12                     Please refer to sifive-blocks-ip-versioning.txt for
   13                     additional details.
   14 - reg             : bus address start and address range size of device
   15 - clocks          : handle to the controller clock; see the note below.
   16                     Mutually exclusive with opencores,ip-clock-frequency
   17 - opencores,ip-clock-frequency: frequency of the controller clock in Hz;
   18                     see the note below. Mutually exclusive with clocks
   19 - #address-cells  : should be <1>
   20 - #size-cells     : should be <0>
   21 
   22 Optional properties:
   23 - interrupts      : interrupt number.
   24 - clock-frequency : frequency of bus clock in Hz; see the note below.
   25                     Defaults to 100 KHz when the property is not specified
   26 - reg-shift       : device register offsets are shifted by this value
   27 - reg-io-width    : io register width in bytes (1, 2 or 4)
   28 - regstep         : deprecated, use reg-shift above
   29 
   30 Note
   31 clock-frequency property is meant to control the bus frequency for i2c bus
   32 drivers, but it was incorrectly used to specify i2c controller input clock
   33 frequency. So the following rules are set to fix this situation:
   34 - if clock-frequency is present and neither opencores,ip-clock-frequency nor
   35   clocks are, then clock-frequency specifies i2c controller clock frequency.
   36   This is to keep backwards compatibility with setups using old DTB. i2c bus
   37   frequency is fixed at 100 KHz.
   38 - if clocks is present it specifies i2c controller clock. clock-frequency
   39   property specifies i2c bus frequency.
   40 - if opencores,ip-clock-frequency is present it specifies i2c controller
   41   clock frequency. clock-frequency property specifies i2c bus frequency.
   42 
   43 Examples:
   44 
   45         i2c0: ocores@a0000000 {
   46                 #address-cells = <1>;
   47                 #size-cells = <0>;
   48                 compatible = "opencores,i2c-ocores";
   49                 reg = <0xa0000000 0x8>;
   50                 interrupts = <10>;
   51                 opencores,ip-clock-frequency = <20000000>;
   52 
   53                 reg-shift = <0>;        /* 8 bit registers */
   54                 reg-io-width = <1>;     /* 8 bit read/write */
   55 
   56                 dummy@60 {
   57                         compatible = "dummy";
   58                         reg = <0x60>;
   59                 };
   60         };
   61 or
   62         i2c0: ocores@a0000000 {
   63                 #address-cells = <1>;
   64                 #size-cells = <0>;
   65                 compatible = "opencores,i2c-ocores";
   66                 reg = <0xa0000000 0x8>;
   67                 interrupts = <10>;
   68                 clocks = <&osc>;
   69                 clock-frequency = <400000>; /* i2c bus frequency 400 KHz */
   70 
   71                 reg-shift = <0>;        /* 8 bit registers */
   72                 reg-io-width = <1>;     /* 8 bit read/write */
   73 
   74                 dummy@60 {
   75                         compatible = "dummy";
   76                         reg = <0x60>;
   77                 };
   78         };

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