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IDAC USER GUIDE

REVISION HISTORY

Revision No.
Description
 Date
1.0
  • Initial release
    		•  05/08/2025
    1.1
  • Add OPP-based boot voltage selection via the string form of init-voltage
    		•  08/19/2026

    1. Overview

    DAC (Digital to Analog Converter) is an electronic device that converts digital signals into analog signals. We usually use DAC to refer to voltage output type DAC (i.e. the output analog signal is voltage), and IDAC to refer to current output type DAC (i.e. the output analog signal is current).

    2. Keyword

    • DAC

      (Digital-to-Analog Converter) A digital to analog converter is an electronic device that converts digital signals into analog signals.

    • IDAC

      (Current Digital-to-Analog Converter) Current Digital to Analog Converter is a type of digital to analog converter that uses current as the output analog signal.

    3. FUNCTION DESCRIPTION

    SGS has two voltage regulation methods: DIV and IDAC. DIV voltage regulation is achieved by controlling 1-2 GPIO to adjust the voltage, with only 2-4 voltage levels available for adjustment. The accuracy between different levels is around 50mV. IDAC voltage regulation can more finely adjust the voltage (with a precision of 10mV or 20mV), and only requires a dedicated GPIO to control up to 30 voltage levels.

    4. HARDWARE CONNECTION INTRODUCTION

    The IDAC hardware module is integrated within the SoC. It is necessary to switch the corresponding jump cap on the development board to IDAC mode to enable IDAC voltage regulation function.

    5. Uboot USAGE INTRODUCTION

    Currently, IDAC driver is not implemented under uboot.

    6. Kernel USAGE INTRODUCTION

    The objects of IDAC voltage regulation include Core Power（VDD_CORE），CPU Power（VDD_CPU），IPU Power（VDD_IPU），DSP Power（VDD_DSP） Wait. The voltage regulation objects supported by different platforms may vary. Taking the example of adjusting CPU Power with IDAC on the PCUPID platform, the following will illustrate.

    6.1. Configure Kennel Config

    1. Enable corresponding driver module:

      The following configurations need to be selected when compiling the kernel:

      Device Drivers  --->
    [*] Sgs SoC platform drivers  --->
        [*] SGS Voltage Controller Driver
         Voltage Regulator Type (IDAC)  --->

    6.2. Configure DTS

    The relevant settings for IDAC to control CPU Power are in the cpu_power node in dts. The parameters in the node are as follows:

    1.    cpu_power {
2.        compatible = "sgs,voltage-idac-ctrl";
3.        vid_gpio = <PAD_PM_GPIO5>;
4.        base_voltage = <1000>;
5.        status = "okay";
6.    }；

    The meanings of the attributes in the cpu_power node are as follows:

    Attribute Desciiption Set Value Notes
    compatible Match driver for driver registration "sgs,voltage-idac-ctrl" Prohibit modification
    vid_gpio GPIO used for configuration Hardware decision Prohibit modification
    base_voltage Reference voltage (in mV) Hardware decision Prohibit modification
    status Select whether to enable the node "okay" or "disabled" Modify as needed

    The core_power node supports selecting the boot voltage from OPP entries via init-voltage. The parameters in the node are as follows:

    1.    core_power {
2.        regulator-name = "core_power";
3.        regulator-min-microvolt = <700000>;
4.        regulator-max-microvolt = <1300000>;
5.        regulator-ramp-delay = <10>;
6.        regulator-always-on;
7.        compatible = "sgs,regulator-idac";
8.        gpio = <PAD_PM_GPIO4>;
9.        base-voltage = <1000000>;   // uV
10.        sample-resistor = <20000>;  // ohm
11.        opp0 = <920000 860000 0x0>;
12.        opp1 = <970000 900000 0x1>;
13.        init-voltage = "opp1";
14.        status = "okay";
15.    };

    The meanings of the attributes in the core_power node are as follows:

    Attribute Description Set Value Notes
    compatible Match driver for driver registration "sgs,regulator-idac" Prohibit modification
    regulator-* Standard regulator properties (name, voltage range, ramp delay, etc.) Hardware decision Refer to kernel regulator documentation
    gpio GPIO used for IDAC control Hardware decision Prohibit modification
    base-voltage Reference voltage (in uV) Hardware decision Prohibit modification
    sample-resistor Sample resistor value (in ohm) Hardware decision Prohibit modification
    opp<name> OPP entries for the boot voltage Provided by SGS Prohibit modification
    init-voltage Initial voltage applied at boot OPP property name string (e.g. "opp1"), or a fixed u32 value (in uV) Selects the OPP entry applied at boot
    status Select whether to enable the node "okay" or "disabled" Modify as needed

    When init-voltage is an OPP property name, the driver applies the voltage of that OPP entry at boot; when it is a u32 value, that fixed voltage (in uV) is applied at boot. If init-voltage is not configured, the driver does not apply any initial voltage at boot.

    6.3. Configure Padmux

    NA

    6.4. Module Usage Introduction

    6.4.1. SYSFS Usage method

    Using sysfs to query/modify CPU power in the kernel, the instructions are as follows:

    • CPU Power

      Dump current CPU power

      cat /sys/devices/system/voltage/cpu_power/voltage_current

1070
    VOLTAGE_DEMANDER_INIT           -
    VOLTAGE_DEMANDER_CPUFREQ        1070
    VOLTAGE_DEMANDER_TEMPERATURE    -
    VOLTAGE_DEMANDER_USER           -

      Query available cpu power

      cat /sys/devices/system/voltage/cpu_power/voltage_available
Vmin(mV)        Vmax(mV)
700         1300

      Set cpu power to 900mV

      echo 900 > /sys/devices/system/voltage/cpu_power/voltage_current

    6.4.2. ioctl Usage method

    N/A

    6.5. Sample Code

    N/A

    7. API Reference

    This functional module provides the following interfaces:

    Parameter Name Description
    set_core_voltage set voltage
    get_core_voltage get voltage

    7.1. set_core_voltage

    • Function

      Set voltage

    • Grammar

      int set_core_voltage(const char *name, VOLTAGE_DEMANDER_E demander, u32 mV)

    • Parameter

      Parameter Name Description
      name The name of the object that needs to be setting，such as ore_power，cpu_power，ipu_power
      demander Requester
      mV Voltage value (unit: mv)

    • Return value

      Return value Description
      0 Successful
      other Fail

    7.2. get_core_voltage

    • Function

      Get voltage

    • Grammar

       int get_core_voltage(const char *name, u32 *mV)

    • Parameter

      Parameter Name Description
      name The name of the object to be queried, such as core_power，cpu_power，ipu_power
      mV The voltage value retrieved is retained in this variable

    • Return value

      Return value Description
      0 Successful
      other Fail

    8. FAQ

    NA