Zephyr Versal SYSMON Driver Implementation

This page provides details on the implementation of the Versal SYSMON Zephyr driver.

Sensor Layer

The sensor driver does not use a subsystem. Instead, the Zephyr sensor framework header (sensor.h) validates the parameters passed and calls the driver API.

https://xilinx-wiki.atlassian.net/wiki/spaces/A/whiteboard/3435855922

Versal SYSMON Node

Note: Node structure is not yet finalized

sysmon@f1270000 {
               compatible = "xlnx,versal-sysmon";
               reg = <0x00 0xf1270000 0x00 0x4000>;
               interrupts = <0x00 0x90 0x04>;
               xlnx,numchannels = [08];
               status = "okay";

               vccint {
                       xlnx,register = [00];
                       xlnx,bipolar;
                       xlnx,name = "vccint";
               };

               vccsoc {
                       xlnx,register = [1f];
                       xlnx,bipolar;
                       xlnx,name = "vccsoc";
               };

               vccram {
                       xlnx,register = [3f];
                       xlnx,bipolar;
                       xlnx,name = "vccram";
               };

               vccaux {
                       xlnx,register = [20];
                       xlnx,bipolar;
                       xlnx,name = "vccaux";
               };

               vccbram {
                       xlnx,register = [5f];
                       xlnx,name = "vccbram";
               };

               gtavaux {
                       xlnx,register = [60];
                       xlnx,name = "gt_avaux";
               };

               gtvccaux {
                       xlnx,register = [40];
                       xlnx,bipolar;
                       xlnx,name = "gt_vccaux";
               };
               vccintir {
                       xlnx,register = [7f];
                       xlnx,bipolar;
                       xlnx,name = "vccint_ir";
               };
       };

Probe Data From Node

In driver we need to assign the compatible string to a zephyr macro, DT_DRV_COMPAT. If the assigned string matches with any one of the DT nodes with status property okay then driver register the Init API to the sensor framework using a framework structure.

Sensor Framework

Sensor framework has a structure where drivers need to register their APIs by following the same protocol used in the structure that follows,

Framework Structure

__subsystem struct sensor_driver_api {
    sensor_attr_set_t attr_set;
    sensor_attr_get_t attr_get;
    sensor_trigger_set_t trigger_set;
    sensor_sample_fetch_t sample_fetch;
    sensor_channel_get_t channel_get;
    sensor_get_decoder_t get_decoder;
    sensor_submit_t submit;
};

Functional Implementation

sensor_attr_set_t

Args: const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, const struct sensor_value *val

Set lower/upper thresholds.
Enable/disable interrupt and configure interrupt mode.
Enable/disable averaging.

sensor_attr_get_t

Args: const struct device *dev, enum sensor_channel chan, enum sensor_attribute attr, const struct sensor_value *val

Get lower/upper thresholds, averaging count, Interrupt mode, and interrupt configuration.

sensor_trigger_set_t

Args: const struct device *dev, const struct sensor_trigger *trig, sensor_trigger_handler_t handler

Register interrupt handler callback based on trigger types.
- Trigger types:
  - SENSOR_TRIG_DATA_READY
  - SENSOR_TRIG_THRESHOLD

sensor_sample_fetch_t

Args: const struct device *dev, enum sensor_channel chan

Read the raw voltage/temperature values and convert them into actual values.
store the data in driver data structure.
- chan types
  - SENSOR_CHAN_VOLTAGE
  - SENSOR_CHAN_DIE_TEMP
  - SENSOR_CHAN_ALL

sensor_channel_get_t

Args: const struct device *dev, enum sensor_channel chan, struct sensor_value *val

Return a useful value for a particular channel, from the driver’s internal data