From f58872f45c36ded048bccc22701b0986019c24d8 Mon Sep 17 00:00:00 2001 From: Marcelo Schmitt Date: Fri, 12 Jul 2024 16:20:36 -0300 Subject: spi: Enable controllers to extend the SPI protocol with MOSI idle configuration The behavior of an SPI controller data output line (SDO or MOSI or COPI (Controller Output Peripheral Input) for disambiguation) is usually not specified when the controller is not clocking out data on SCLK edges. However, there do exist SPI peripherals that require specific MOSI line state when data is not being clocked out of the controller. Conventional SPI controllers may set the MOSI line on SCLK edges then bring it low when no data is going out or leave the line the state of the last transfer bit. More elaborated controllers are capable to set the MOSI idle state according to different configurable levels and thus are more suitable for interfacing with demanding peripherals. Add SPI mode bits to allow peripherals to request explicit MOSI idle state when needed. When supporting a particular MOSI idle configuration, the data output line state is expected to remain at the configured level when the controller is not clocking out data. When a device that needs a specific MOSI idle state is identified, its driver should request the MOSI idle configuration by setting the proper SPI mode bit. Acked-by: Nuno Sa Reviewed-by: Jonathan Cameron Reviewed-by: David Lechner Tested-by: David Lechner Signed-off-by: Marcelo Schmitt Link: https://patch.msgid.link/9802160b5e5baed7f83ee43ac819cb757a19be55.1720810545.git.marcelo.schmitt@analog.com Signed-off-by: Mark Brown --- Documentation/spi/spi-summary.rst | 83 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) (limited to 'Documentation') diff --git a/Documentation/spi/spi-summary.rst b/Documentation/spi/spi-summary.rst index 7f8accfae6f9..6e21e6f86912 100644 --- a/Documentation/spi/spi-summary.rst +++ b/Documentation/spi/spi-summary.rst @@ -614,6 +614,89 @@ queue, and then start some asynchronous transfer engine (unless it's already running). +Extensions to the SPI protocol +------------------------------ +The fact that SPI doesn't have a formal specification or standard permits chip +manufacturers to implement the SPI protocol in slightly different ways. In most +cases, SPI protocol implementations from different vendors are compatible among +each other. For example, in SPI mode 0 (CPOL=0, CPHA=0) the bus lines may behave +like the following: + +:: + + nCSx ___ ___ + \_________________________________________________________________/ + • • + • • + SCLK ___ ___ ___ ___ ___ ___ ___ ___ + _______/ \___/ \___/ \___/ \___/ \___/ \___/ \___/ \_____ + • : ; : ; : ; : ; : ; : ; : ; : ; • + • : ; : ; : ; : ; : ; : ; : ; : ; • + MOSI XXX__________ _______ _______ ________XXX + 0xA5 XXX__/ 1 \_0_____/ 1 \_0_______0_____/ 1 \_0_____/ 1 \_XXX + • ; ; ; ; ; ; ; ; • + • ; ; ; ; ; ; ; ; • + MISO XXX__________ _______________________ _______ XXX + 0xBA XXX__/ 1 \_____0_/ 1 1 1 \_____0__/ 1 \____0__XXX + +Legend:: + + • marks the start/end of transmission; + : marks when data is clocked into the peripheral; + ; marks when data is clocked into the controller; + X marks when line states are not specified. + +In some few cases, chips extend the SPI protocol by specifying line behaviors +that other SPI protocols don't (e.g. data line state for when CS is not +asserted). Those distinct SPI protocols, modes, and configurations are supported +by different SPI mode flags. + +MOSI idle state configuration +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Common SPI protocol implementations don't specify any state or behavior for the +MOSI line when the controller is not clocking out data. However, there do exist +peripherals that require specific MOSI line state when data is not being clocked +out. For example, if the peripheral expects the MOSI line to be high when the +controller is not clocking out data (``SPI_MOSI_IDLE_HIGH``), then a transfer in +SPI mode 0 would look like the following: + +:: + + nCSx ___ ___ + \_________________________________________________________________/ + • • + • • + SCLK ___ ___ ___ ___ ___ ___ ___ ___ + _______/ \___/ \___/ \___/ \___/ \___/ \___/ \___/ \_____ + • : ; : ; : ; : ; : ; : ; : ; : ; • + • : ; : ; : ; : ; : ; : ; : ; : ; • + MOSI _____ _______ _______ _______________ ___ + 0x56 \_0_____/ 1 \_0_____/ 1 \_0_____/ 1 1 \_0_____/ + • ; ; ; ; ; ; ; ; • + • ; ; ; ; ; ; ; ; • + MISO XXX__________ _______________________ _______ XXX + 0xBA XXX__/ 1 \_____0_/ 1 1 1 \_____0__/ 1 \____0__XXX + +Legend:: + + • marks the start/end of transmission; + : marks when data is clocked into the peripheral; + ; marks when data is clocked into the controller; + X marks when line states are not specified. + +In this extension to the usual SPI protocol, the MOSI line state is specified to +be kept high when CS is asserted but the controller is not clocking out data to +the peripheral and also when CS is not asserted. + +Peripherals that require this extension must request it by setting the +``SPI_MOSI_IDLE_HIGH`` bit into the mode attribute of their ``struct +spi_device`` and call spi_setup(). Controllers that support this extension +should indicate it by setting ``SPI_MOSI_IDLE_HIGH`` in the mode_bits attribute +of their ``struct spi_controller``. The configuration to idle MOSI low is +analogous but uses the ``SPI_MOSI_IDLE_LOW`` mode bit. + + THANKS TO --------- Contributors to Linux-SPI discussions include (in alphabetical order, -- cgit v1.3.1 From 96472f18a4affdaff5013a836c48375f1eddb4a4 Mon Sep 17 00:00:00 2001 From: Marcelo Schmitt Date: Fri, 12 Jul 2024 16:22:00 -0300 Subject: dt-bindings: iio: adc: Add AD4000 Add device tree documentation for AD4000 series of ADC devices. Reviewed-by: Conor Dooley Signed-off-by: Marcelo Schmitt Reviewed-by: David Lechner Link: https://patch.msgid.link/98c82e0a2a868a1578989fe69527347aa92083d7.1720810545.git.marcelo.schmitt@analog.com Signed-off-by: Mark Brown --- .../devicetree/bindings/iio/adc/adi,ad4000.yaml | 197 +++++++++++++++++++++ MAINTAINERS | 7 + 2 files changed, 204 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml new file mode 100644 index 000000000000..e413a9d8d2a2 --- /dev/null +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml @@ -0,0 +1,197 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/iio/adc/adi,ad4000.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Analog Devices AD4000 and similar Analog to Digital Converters + +maintainers: + - Marcelo Schmitt + +description: | + Analog Devices AD4000 family of Analog to Digital Converters with SPI support. + Specifications can be found at: + https://www.analog.com/media/en/technical-documentation/data-sheets/ad4000-4004-4008.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/ad4001-4005.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/ad4002-4006-4010.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/ad4003-4007-4011.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/ad4020-4021-4022.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4001.pdf + https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4003.pdf + +$ref: /schemas/spi/spi-peripheral-props.yaml# + +properties: + compatible: + oneOf: + - const: adi,ad4000 + - items: + - enum: + - adi,ad4004 + - adi,ad4008 + - const: adi,ad4000 + + - const: adi,ad4001 + - items: + - enum: + - adi,ad4005 + - const: adi,ad4001 + + - const: adi,ad4002 + - items: + - enum: + - adi,ad4006 + - adi,ad4010 + - const: adi,ad4002 + + - const: adi,ad4003 + - items: + - enum: + - adi,ad4007 + - adi,ad4011 + - const: adi,ad4003 + + - const: adi,ad4020 + - items: + - enum: + - adi,ad4021 + - adi,ad4022 + - const: adi,ad4020 + + - const: adi,adaq4001 + + - const: adi,adaq4003 + + reg: + maxItems: 1 + + spi-max-frequency: + maximum: 102040816 # for VIO > 2.7 V, 81300813 for VIO > 1.7 V + + adi,sdi-pin: + $ref: /schemas/types.yaml#/definitions/string + enum: [ high, low, cs, sdi ] + default: sdi + description: + Describes how the ADC SDI pin is wired. A value of "sdi" indicates that + the ADC SDI is connected to host SDO. "high" indicates that the ADC SDI + pin is hard-wired to logic high (VIO). "low" indicates that it is + hard-wired low (GND). "cs" indicates that the ADC SDI pin is connected to + the host CS line. + + '#daisy-chained-devices': true + + vdd-supply: + description: A 1.8V supply that powers the chip (VDD). + + vio-supply: + description: + A 1.8V to 5.5V supply for the digital inputs and outputs (VIO). + + ref-supply: + description: + A 2.5 to 5V supply for the external reference voltage (REF). + + cnv-gpios: + description: + When provided, this property indicates the GPIO that is connected to the + CNV pin. + maxItems: 1 + + adi,high-z-input: + type: boolean + description: + High-Z mode allows the amplifier and RC filter in front of the ADC to be + chosen based on the signal bandwidth of interest, rather than the settling + requirements of the switched capacitor SAR ADC inputs. + + adi,gain-milli: + description: | + The hardware gain applied to the ADC input (in milli units). + The gain provided by the ADC input scaler is defined by the hardware + connections between chip pins OUT+, R1K-, R1K1-, R1K+, R1K1+, and OUT-. + If not present, default to 1000 (no actual gain applied). + $ref: /schemas/types.yaml#/definitions/uint16 + enum: [454, 909, 1000, 1900] + default: 1000 + + interrupts: + description: + The SDO pin can also function as a busy indicator. This node should be + connected to an interrupt that is triggered when the SDO line goes low + while the SDI line is high and the CNV line is low ("3-wire" mode) or the + SDI line is low and the CNV line is high ("4-wire" mode); or when the SDO + line goes high while the SDI and CNV lines are high (chain mode), + maxItems: 1 + +required: + - compatible + - reg + - vdd-supply + - vio-supply + - ref-supply + +allOf: + # The configuration register can only be accessed if SDI is connected to MOSI + - if: + required: + - adi,sdi-pin + then: + properties: + adi,high-z-input: false + # chain mode has lower SCLK max rate + - if: + required: + - '#daisy-chained-devices' + then: + properties: + spi-max-frequency: + maximum: 50000000 # for VIO > 2.7 V, 40000000 for VIO > 1.7 V + # Gain property only applies to ADAQ devices + - if: + properties: + compatible: + not: + contains: + enum: + - adi,adaq4001 + - adi,adaq4003 + then: + properties: + adi,gain-milli: false + +unevaluatedProperties: false + +examples: + - | + #include + spi { + #address-cells = <1>; + #size-cells = <0>; + adc@0 { + compatible = "adi,ad4020"; + reg = <0>; + spi-max-frequency = <71000000>; + vdd-supply = <&supply_1_8V>; + vio-supply = <&supply_1_8V>; + ref-supply = <&supply_5V>; + adi,sdi-pin = "cs"; + cnv-gpios = <&gpio0 88 GPIO_ACTIVE_HIGH>; + }; + }; + - | + spi { + #address-cells = <1>; + #size-cells = <0>; + adc@0 { + compatible = "adi,adaq4003"; + reg = <0>; + spi-max-frequency = <80000000>; + vdd-supply = <&supply_1_8V>; + vio-supply = <&supply_1_8V>; + ref-supply = <&supply_5V>; + adi,high-z-input; + adi,gain-milli = /bits/ 16 <454>; + }; + }; diff --git a/MAINTAINERS b/MAINTAINERS index 42decde38320..bc5d242deb29 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1202,6 +1202,13 @@ W: https://ez.analog.com/linux-software-drivers F: Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml F: drivers/iio/dac/ad3552r.c +ANALOG DEVICES INC AD4000 DRIVER +M: Marcelo Schmitt +L: linux-iio@vger.kernel.org +S: Supported +W: https://ez.analog.com/linux-software-drivers +F: Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml + ANALOG DEVICES INC AD4130 DRIVER M: Cosmin Tanislav L: linux-iio@vger.kernel.org -- cgit v1.3.1