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dt-bindings: i2c: add support for 'i2c-gate' subnode

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Handle i2c gates similarly to how i2c arbitrators are handled.
This gets rid of a pointless 'reg' property for i2c gates.

I.e. this new and more compact style

        some-gate {
                i2c-gate {
                        #address-cells = <1>;
                        #size-cells = <0>;

                        some-i2c-device@50 {
                                reg = <0x50>;
                        };
                };
        };

instead of the old

        some-gate {
                #address-cells = <1>;
                #size-cells = <0>;

                i2c@0 {
                        reg = <0>;

                        #address-cells = <1>;
                        #size-cells = <0>;

                        some-i2c-device@50 {
                                reg = <0x50>;
                        };
                };
        };

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
This commit is contained in:
Peter Rosin 2016-07-08 12:13:49 +02:00
parent e8813c15be
commit 0ac8eb6452
2 changed files with 42 additions and 0 deletions
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41
Documentation/devicetree/bindings/i2c/i2c-gate.txt Normal file
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@ -0,0 +1,41 @@
An i2c gate is useful to e.g. reduce the digital noise for RF tuners connected
to the i2c bus. Gates are similar to arbitrators in that you need to perform
some kind of operation to access the i2c bus past the arbitrator/gate, but
there are no competing masters to consider for gates and therefore there is
no arbitration happening for gates.
Common i2c gate properties.
- i2c-gate child node
Required properties for the i2c-gate child node:
- #address-cells = <1>;
- #size-cells = <0>;
Optional properties for i2c-gate child node:
- Child nodes conforming to i2c bus binding
Example :
/*
An Invensense mpu9150 at address 0x68 featuring an on-chip Asahi
Kasei ak8975 compass behind a gate.
*/
mpu9150@68 {
compatible = "invensense,mpu9150";
reg = <0x68>;
interrupt-parent = <&gpio1>;
interrupts = <18 1>;
i2c-gate {
#address-cells = <1>;
#size-cells = <0>;
ax8975@c {
compatible = "ak,ak8975";
reg = <0x0c>;
};
};
};

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@ -5668,6 +5668,7 @@ F: Documentation/i2c/i2c-topology
F: Documentation/i2c/muxes/
F: Documentation/devicetree/bindings/i2c/i2c-mux*
F: Documentation/devicetree/bindings/i2c/i2c-arb*
F: Documentation/devicetree/bindings/i2c/i2c-gate*
F: drivers/i2c/i2c-mux.c
F: drivers/i2c/muxes/
F: include/linux/i2c-mux.h