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74 lines
2.4 KiB
74 lines
2.4 KiB
Register-based I2C Bus Mux |
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This binding describes an I2C bus multiplexer that uses a single register |
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to route the I2C signals. |
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Required properties: |
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- compatible: i2c-mux-reg |
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- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side |
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port is connected to. |
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* Standard I2C mux properties. See i2c-mux.yaml in this directory. |
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* I2C child bus nodes. See i2c-mux.yaml in this directory. |
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Optional properties: |
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- reg: this pair of <offset size> specifies the register to control the mux. |
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The <offset size> depends on its parent node. It can be any memory-mapped |
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address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the |
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resource of this device will be used. |
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- little-endian: The existence indicates the register is in little endian. |
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- big-endian: The existence indicates the register is in big endian. |
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If both little-endian and big-endian are omitted, the endianness of the |
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CPU will be used. |
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- write-only: The existence indicates the register is write-only. |
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- idle-state: value to set the muxer to when idle. When no value is |
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given, it defaults to the last value used. |
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Whenever an access is made to a device on a child bus, the value set |
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in the relevant node's reg property will be output to the register. |
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If an idle state is defined, using the idle-state (optional) property, |
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whenever an access is not being made to a device on a child bus, the |
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register will be set according to the idle value. |
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If an idle state is not defined, the most recently used value will be |
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left programmed into the register. |
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Example of a mux on PCIe card, the host is a powerpc SoC (big endian): |
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i2c-mux { |
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/* the <offset size> depends on the address translation |
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* of the parent device. If omitted, device resource |
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* will be used instead. The size is to determine |
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* whether iowrite32, iowrite16, or iowrite8 will be used. |
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*/ |
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reg = <0x6028 0x4>; |
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little-endian; /* little endian register on PCIe */ |
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compatible = "i2c-mux-reg"; |
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#address-cells = <1>; |
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#size-cells = <0>; |
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i2c-parent = <&i2c1>; |
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i2c@0 { |
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reg = <0>; |
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#address-cells = <1>; |
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#size-cells = <0>; |
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si5338: clock-generator@70 { |
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compatible = "silabs,si5338"; |
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reg = <0x70>; |
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/* other stuff */ |
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}; |
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}; |
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i2c@1 { |
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/* data is written using iowrite32 */ |
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reg = <1>; |
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#address-cells = <1>; |
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#size-cells = <0>; |
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si5338: clock-generator@70 { |
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compatible = "silabs,si5338"; |
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reg = <0x70>; |
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/* other stuff */ |
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}; |
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}; |
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};
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