Pad Voltage DT BindingΒΆ

Tegra pins and pads are designed to support multiple voltage levels at a given interface. They can operate at 1.2 volts (V), 1.8 V or 3.3 V. Based on the interface and power tree of a given platform, the software must write to the correct voltage of these pads to enable interface. If pad voltage is higher than the I/O power rail, then the pin does not work on that level. If pad voltage is lower than the I/O power rail, then it can damage the SoC pads. Consequently, configuring the correct pad voltage is required based on the power tree.

The Pad voltage DTSI is generated by using the pinmux spread sheet.

The prod configuration files are in the hardware/nvidia/platform/t23x/<platform>/bct/ directory.

The contrast in the new DTS format is because of the pinmux sheet output.

Here is the example of the new DTS format of pad-voltage configuration file:

/*This dtsi file was generated by e3360_1099_slt_a01.xlsm Revision: 126 */
/ {
    pmc@c360000 {
          io-pad-defaults {
                  sdmmc1_hv {
                          nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_8V>;
                  };
                      sdmmc3_hv {
                          nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_8V>;
                      };
                      eqos {
                          nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_8V>;
                      };
                      qspi {
                         nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_8V>;
                      };
                      debug {
                          nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_8V>;
                      };
                      ao_hv {
                         nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_3_3V>;
                      };
                      audio_hv {
                         nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_3_3V>;
                      };
                      ufs {
                          nvidia,io-pad-init-voltage = <IO_PAD_VOLTAGE_1_2V>;
                      };

       };
   };
};

Here is the previous CFG format:

pad-voltage.major = 1;
pad-voltage.minor = 0;
pad-voltage.0x0c36003c = 0x0000003e; // PMC_IMPL_E_18V_PWR_0
pad-voltage.0x0c360040 = 0x00000079; // PMC_IMPL_E_33V_PWR_0