@@ -129,6 +129,25 @@ properties:
line goes high while the SDI and CNV lines are high (chain mode),
maxItems: 1
+ # optional SPI offload support for use with AXI SPI Engine
+
+ spi-offloads:
+ maxItems: 1
+
+ dmas:
+ maxItems: 1
+ description: RX DMA Channel for receiving a samples from the SPI offload.
+
+ dma-names:
+ const: rx
+
+ clocks:
+ maxItems: 1
+ description: Clock to trigger the SPI offload for reading a sample.
+
+ clock-names:
+ const: trigger
+
required:
- compatible
- reg
@@ -190,6 +209,23 @@ allOf:
properties:
turbo-gpios: false
+ # certain properties are for SPI offload use only
+ - if:
+ required:
+ - spi-offloads
+ then:
+ required:
+ - dmas
+ - dma-names
+ - clocks
+ - clock-names
+ else:
+ properties:
+ dmas: false
+ dma-names: false
+ clocks: false
+ clock-names: false
+
unevaluatedProperties: false
examples:
@@ -211,3 +247,25 @@ examples:
turbo-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
};
};
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ adc@0 {
+ compatible = "adi,ad7944";
+ reg = <0>;
+ spi-cpha;
+ spi-max-frequency = <111111111>;
+ adi,spi-mode = "single";
+ avdd-supply = <&supply_2_5V>;
+ dvdd-supply = <&supply_2_5V>;
+ vio-supply = <&supply_1_8V>;
+ bvdd-supply = <&supply_5V>;
+ spi-offloads = <0>;
+ dmas = <&dma 0>;
+ dma-names = "rx";
+ clocks = <&trigger_clk>;
+ clock-names = "trigger";
+ };
+ };
To enable capturing data at high rates, the AD7944 is frequently used with the AXI SPI Engine IP core. This patch adds the properties needed to describe the SPI offload configuration in the device tree. The clock trigger and DMA buffer for rx data are external to the SPI controller and specific to the application so the are included in the peripheral bindings. Signed-off-by: David Lechner <dlechner@baylibre.com> --- v2 changes: This is a new patch that partially replaces "dt-bindings: iio: offload: add binding for PWM/DMA triggered buffer". In the previous review, it was suggested that having a separate binding and object node for the offload was overcomplicated. So instead this opts to use the proposed standard spi-offloads property as a flag to allow the SPI periperhal node require additional properties that are resources that are physically connected to the SPI offload. On a whim, I also changed pwms to clocks in the binding. The thinking being that we only care about the frequency (it determines the sample rate) so a clock made more sense and might allow more flexibility in the future. But since the actual hardware we have is a PWM, we would have to use "pwm-clock" in the devicetree to make the PWM act as a clock. But it turns out that the pwm-clock driver does not support setting the frequency, so we would have to do more work to actually be able to use this binding in practice. --- .../devicetree/bindings/iio/adc/adi,ad7944.yaml | 58 ++++++++++++++++++++++ 1 file changed, 58 insertions(+)