iio: humidity: si7020: Check device property for skipping reset in probe

I2C commands issued after the SI7020 is starting up or after reset can potentially upset the startup sequence. Therefore, the host needs to wait for the startup sequence to finish before issuing further i2c commands. This is impractical in cases where the SI7020 is on a shared bus or behind a mux, which may switch channels at any time (generating I2C traffic). Therefore, check for a device property that indicates that the driver should skip resetting the device when probing.

Eddie James (2):
dt-bindings: iio: humidity: Add si7020 bindings
iio: humidity: si7020: Check device property for skipping reset in probe

 .../bindings/iio/humidity/silabs,si7020.yaml  | 42 +++++++++++++++++++
 drivers/iio/humidity/si7020.c                 | 14 ++++---
 2 files changed, 50 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/humidity/silabs,si7020.yaml

2.27.0

Document the si7020 bindings with a new "silabs,skip-reset" property.

---
 .../bindings/iio/humidity/silabs,si7020.yaml  | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/humidity/silabs,si7020.yaml

new file mode 100644
index 000000000000..ab53bb8d9606
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/humidity/silabs,si7020.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SI7020 humidity + temperature sensor
+
+maintainers:
+  - David Barksdale <[email protected]>
+
+description: |
+   The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
+   are i2c devices which have an identical programming interface for
+   measuring relative humidity and temperature.
+
+properties:
+  compatible:
+    const: silabs,si7020
+
+  reg:
+    maxItems: 1
+
+  siliabs,skip-reset:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Disables resetting of the device during probe
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    si7021-a20@40 {
+        silabs,skip-reset;
+        compatible = "silabs,si7020";
+        reg = <0x40>;
+    };
+...

2.27.0

I missed the entry in trivial-devices.txt. I can push a v2 or a separate patch for that.

Eddie

In this patch, please. Anyway you need v2.

Best regards,
Krzysztof

My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check' on your patch (DT_CHECKER_FLAGS is new in v5.13):

yamllint warnings/errors:

dtschema/dtc warnings/errors:
Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dts:21.13-26: Warning (reg_format): /example-0/si7021-a20@40:reg: property has invalid length (4 bytes) (#address-cells == 1, #size-cells == 1) Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: Warning (pci_device_reg): Failed prerequisite 'reg_format' Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: Warning (pci_device_bus_num): Failed prerequisite 'reg_format' Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: Warning (simple_bus_reg): Failed prerequisite 'reg_format' Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: Warning (i2c_bus_reg): Failed prerequisite 'reg_format' Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: Warning (spi_bus_reg): Failed prerequisite 'reg_format' /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: example-0: si7021-a20@40:reg:0: [64] is too short
From schema: /usr/local/lib/python3.10/dist-packages/dtschema/schemas/reg.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: si7021-a20@40: 'silabs,skip-reset' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/iio/humidity/silabs,si7020.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/iio/humidity/silabs,si7020.example.dtb: si7021-a20@40: 'silabs,skip-reset' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/trivial-devices.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/patch/

This check can fail if there are any dependencies. The base for a patch series is generally the most recent rc1.

If you already ran 'make dt_binding_check' and didn't see the above error(s), then make sure 'yamllint' is installed and dt-schema is up to date:

pip3 install dtschema --upgrade

Please check and re-submit.

Thank you for your patch. There is something to discuss/improve.

I2C commands issued after the SI7020 is starting up or after reset can potentially upset the startup sequence. Therefore, the host needs to wait for the startup sequence to finish before issuing further i2c commands. This is impractical in cases where the SI7020 is on a shared bus or behind a mux, which may switch channels at any time (generating I2C traffic). Therefore, check for a device property that indicates that the driver should skip resetting the device when probing.

---
 drivers/iio/humidity/si7020.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

index ab6537f136ba..49f6a1b1f5c4 100644
@@ -115,12 +115,14 @@ static int si7020_probe(struct i2c_client *client,
 				     I2C_FUNC_SMBUS_READ_WORD_DATA))
 		return -EOPNOTSUPP;
 
-	/* Reset device, loads default settings. */
-	ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
-	if (ret < 0)
-		return ret;
-	/* Wait the maximum power-up time after software reset. */
-	msleep(15);
+	if (!device_property_read_bool(&client->dev, "silabs,skip-reset")) {
+		/* Reset device, loads default settings. */
+		ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
+		if (ret < 0)
+			return ret;
+		/* Wait the maximum power-up time after software reset. */
+		msleep(15);
+	}
 
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)

2.27.0