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All chips supported by this driver clock data out on the falling edge and latch data in on the rising edge, hence SPI mode (0,0) or (1,1) must be used. Furthermore, none of the chips has an internal reference voltage regulator, so an external supply is always required and needs to be specified in the device tree lest the IIO "scale" in sysfs cannot be calculated. Document these requirements in the device tree binding, add compatible strings for the newly supported mcp3550/1/3 and explain that SPI mode (0,0) should be preferred for these chips. Cc: Mathias Duckeck <m.duckeck@kunbus.de> Signed-off-by: Lukas Wunner <lukas@wunner.de> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
58 lines
1.5 KiB
Plaintext
58 lines
1.5 KiB
Plaintext
* Microchip Analog to Digital Converter (ADC)
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The node for this driver must be a child node of a SPI controller, hence
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all mandatory properties described in
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Documentation/devicetree/bindings/spi/spi-bus.txt
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must be specified.
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Required properties:
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- compatible: Must be one of the following, depending on the
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model:
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"mcp3001" (DEPRECATED)
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"mcp3002" (DEPRECATED)
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"mcp3004" (DEPRECATED)
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"mcp3008" (DEPRECATED)
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"mcp3201" (DEPRECATED)
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"mcp3202" (DEPRECATED)
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"mcp3204" (DEPRECATED)
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"mcp3208" (DEPRECATED)
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"mcp3301" (DEPRECATED)
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"microchip,mcp3001"
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"microchip,mcp3002"
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"microchip,mcp3004"
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"microchip,mcp3008"
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"microchip,mcp3201"
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"microchip,mcp3202"
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"microchip,mcp3204"
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"microchip,mcp3208"
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"microchip,mcp3301"
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"microchip,mcp3550-50"
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"microchip,mcp3550-60"
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"microchip,mcp3551"
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"microchip,mcp3553"
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NOTE: The use of the compatibles with no vendor prefix
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is deprecated and only listed because old DT use them.
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- spi-cpha, spi-cpol (boolean):
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Either SPI mode (0,0) or (1,1) must be used, so specify
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none or both of spi-cpha, spi-cpol. The MCP3550/1/3
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is more efficient in mode (1,1) as only 3 instead of
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4 bytes need to be read from the ADC, but not all SPI
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masters support it.
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- vref-supply: Phandle to the external reference voltage supply.
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Examples:
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spi_controller {
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mcp3x0x@0 {
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compatible = "mcp3002";
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reg = <0>;
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spi-max-frequency = <1000000>;
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vref-supply = <&vref_reg>;
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};
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};
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