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author | York Sun <yorksun@freescale.com> | 2015-08-17 11:53:48 -0700 |
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committer | Wolfram Sang <wsa@the-dreams.de> | 2015-08-24 14:05:18 +0200 |
commit | b3fdd32799d834e2626fae087906e886037350c6 (patch) | |
tree | 38d3df37fe04e8631ba955a3dfd6ed2a80dd7ff8 /Documentation/devicetree/bindings | |
parent | 7a59b00a0906945f7fe25a10332ac0820491a0c3 (diff) | |
download | linux-stable-b3fdd32799d834e2626fae087906e886037350c6.tar.gz linux-stable-b3fdd32799d834e2626fae087906e886037350c6.tar.bz2 linux-stable-b3fdd32799d834e2626fae087906e886037350c6.zip |
i2c: mux: Add register-based mux i2c-mux-reg
Based on i2c-mux-gpio driver, similarly the register-based mux
switch from one bus to another by setting a single register.
The register can be on PCIe bus, local bus, or any memory-mapped
address. The endianness of such register can be specified in device
tree if used, or in platform data.
Signed-off-by: York Sun <yorksun@freescale.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'Documentation/devicetree/bindings')
-rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt new file mode 100644 index 000000000000..688783fbe696 --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt @@ -0,0 +1,74 @@ +Register-based I2C Bus Mux + +This binding describes an I2C bus multiplexer that uses a single register +to route the I2C signals. + +Required properties: +- compatible: i2c-mux-reg +- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side + port is connected to. +* Standard I2C mux properties. See mux.txt in this directory. +* I2C child bus nodes. See mux.txt in this directory. + +Optional properties: +- reg: this pair of <offset size> specifies the register to control the mux. + The <offset size> depends on its parent node. It can be any memory-mapped + address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the + resource of this device will be used. +- little-endian: The existence indicates the register is in little endian. +- big-endian: The existence indicates the register is in big endian. + If both little-endian and big-endian are omitted, the endianness of the + CPU will be used. +- write-only: The existence indicates the register is write-only. +- idle-state: value to set the muxer to when idle. When no value is + given, it defaults to the last value used. + +Whenever an access is made to a device on a child bus, the value set +in the revelant node's reg property will be output to the register. + +If an idle state is defined, using the idle-state (optional) property, +whenever an access is not being made to a device on a child bus, the +register will be set according to the idle value. + +If an idle state is not defined, the most recently used value will be +left programmed into the register. + +Example of a mux on PCIe card, the host is a powerpc SoC (big endian): + + i2c-mux { + /* the <offset size> depends on the address translation + * of the parent device. If omitted, device resource + * will be used instead. The size is to determine + * whether iowrite32, iowrite16, or iowrite8 will be used. + */ + reg = <0x6028 0x4>; + little-endian; /* little endian register on PCIe */ + compatible = "i2c-mux-reg"; + #address-cells = <1>; + #size-cells = <0>; + i2c-parent = <&i2c1>; + i2c@0 { + reg = <0>; + #address-cells = <1>; + #size-cells = <0>; + + si5338: clock-generator@70 { + compatible = "silabs,si5338"; + reg = <0x70>; + /* other stuff */ + }; + }; + + i2c@1 { + /* data is written using iowrite32 */ + reg = <1>; + #address-cells = <1>; + #size-cells = <0>; + + si5338: clock-generator@70 { + compatible = "silabs,si5338"; + reg = <0x70>; + /* other stuff */ + }; + }; + }; |