topic iMX8QXP ADC function abnormal in i.MX Processors

iMX8QXP ADC function abnormal

liuyonggang — Wed, 05 Feb 2020 11:28:45 GMT

Platform:iMX8QXP

Build enviroment:yocto

question:config ADC_IN0~ADC_IN5 as ADC channel,but the function is abnormal.

1.confirm CONFIG_IMX8QXP_ADC=y in arch/arm64/configs/defconfig;

2.add dts info in fsl-imx8qxp-ctx0800-rohs.dtsi file as followings:
&iomuxc {
[...]

pinctrl_adc0: adc0grp {
      fsl,pins = <
         SC_P_ADC_IN0_ADMA_ADC_IN0 0xc0000060
         SC_P_ADC_IN1_ADMA_ADC_IN1 0xc0000060
         SC_P_ADC_IN2_ADMA_ADC_IN2 0xc0000060
         SC_P_ADC_IN3_ADMA_ADC_IN3 0xc0000060
         SC_P_ADC_IN4_ADMA_ADC_IN4 0xc0000060
         SC_P_ADC_IN5_ADMA_ADC_IN5 0xc0000060
      >;
   };
};

&adc0 {
   pinctrl-names = "default";
   pinctrl-0 = <&pinctrl_adc0>;
   digi,adc-ch-list = <0 1 2 3 4 5>;
   status = "okay";
};

3.I can see /dev/iio:device0 device node;

4.root@CTX0800-RoHS:~# cat /sys/bus/iio/devices/iio\:device0/in_voltage_scale
1048.575927734

The value is abnormal.

5.check kernel startup log:

[ 3.085389] imx8qxp-pinctrl iomuxc: pin_config_set op failed for pin 100
[ 3.092240] imx8qxp_adc 5a880000.adc: Error applying setting, reverse things back
[ 3.100523] imx8qxp_adc 5a880000.adc: 5a880000.adc supply vref not found, using dummy regulator

as above info(point 5),ADC_IN0(pin 100) configration are conflicts with somewhere.Moreover ADC supply vref is abnormal.

Can someone help me?

BRs!

Johnny

Re: iMX8QXP ADC function abnormal

igorpadykov — Wed, 05 Feb 2020 23:38:47 GMT

Hi Johnny

please check that latest rev.C0 revision used in the case and

latest linux L4.14.98_2.3.0 supporting that revision

Linux 4.14.98_2.3.0 Documentation

Best regards
igor
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Re: iMX8QXP ADC function abnormal

liuyonggang — Fri, 07 Feb 2020 08:37:31 GMT

Hi igor,

Tks for your suggestion.

I researched Linux 4.14.98_2.3.0 Documentation carefully,But They are unuseful for me.

BRs

Johnny