i.MX28 5V0 voltage regulator powering an USB interface (GPIO pin)

[gordanmarkus]

Hello,

I'm currently experiencing issues trying to use one of i.MX28 GPIO pins to produce a 5V output (using a voltage regulator) in order to power an USB interface (a camera board to be precise). This is a custom board and the USB power pin in question is GPIO3_28 (MX28_PAD_PWM3__GPIO_3_28) and the over-current pin is connected to GPIO3_18 (MX28_PAD_PWM2__USB1_OVERCURRENT). The kernel in question is 3.14-rc5

The device tree definitions vital to this issue are the following:

PIN DEFINITIONS:

pinctrl@80018000 {

  pinctrl-names = "default";

  pinctrl-0 = <&hog_pins_a>;

hog_pins_a: hog@0 {

  reg = <0>;

  fsl,pinmux-ids = <

       0x2053 /* MX28_PAD_SSP0_DATA5__GPIO_2_5 */

       0x2063 /* MX28_PAD_SSP0_DATA6__GPIO_2_6 */

       0x2073 /* MX28_PAD_SSP0_DATA7__GPIO_2_7 */

       0x3043 /* MX28_PAD_AUART1_RX__GPIO_3_4 */

       0x3053 /* MX28_PAD_AUART1_TX__GPIO_3_5 */

       0x31c3  /* MX28_PAD_PWM3__GPIO_3_28 */    

       >;

  fsl,drive-strength = <MXS_DRIVE_4mA>;

  fsl,voltage = <MXS_VOLTAGE_HIGH>;

  fsl,pull-up = <MXS_PULL_DISABLE>;

  };

usbphy1_pins: usbphy1-pins {

  fsl,pinmux-ids = <

       MX28_PAD_PWM2__USB1_OVERCURRENT

  >;

  fsl,drive-strength = <MXS_DRIVE_12mA>;

  fsl,voltage = <MXS_VOLTAGE_HIGH>;

  fsl,pull-up = <MXS_PULL_DISABLE>;

  };

USBPHY DEFINITON:

usbphy1: usbphy@8007e000 {

  pinctrl-names = "default";

  pinctrl-0 = <&usbphy1_pins>;

  status = "okay";

  };

USB DEFINITION:

usb1: usb@80090000 {

  vbus-supply = <&reg_usb1_vbus>;

  dr_mode = "host";

  disable-over-current;

  status = "okay";

  };

REGULATOR DEFINITION:

reg_usb1_vbus: usb1_vbus {

  compatible = "regulator-fixed";

  regulator-name = "usb1_vbus";

  regulator-min-microvolt = <5000000>;

  regulator-max-microvolt = <5000000>;

  gpio = <&gpio3 28 0>;

  enable-active-high;

  };

IFCONFIG:

(usb0 -> ../../devices/soc0/80080000.ahb/80090000.usb/ci_hdrc.1/usb2/2-1/2-1:1.0/net/usb0)

usb0   Link encap:Ethernet  HWaddr 8A:D8:73:29:3F:F5

          inet addr:172.16.245.114  Bcast:172.16.255.255  Mask:255.255.0.0

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:0 errors:0 dropped:0 overruns:0 frame:0

          TX packets:18 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          RX bytes:0 (0.0 B)  TX bytes:3919 (3.8 KiB)

The USB device is recognized (ci_hdrc device) but the voltage that I measure is 3V3 and not 5V0.  Maybe I am overlooking the bindings from USB/PHY driver to the regulator. I would gladly appreciate any help with this issue.

Regards,

Gordan Markuš

[gusarambula · Accepted solution]

Unfortunately the PWM pins cannot provide 5V. The wording on the datasheet may be misinterpreted as it does not provide enough information on this feature.

“PMU Generates USB-Host 5-V from Li-Ion battery (using PWM).”

http://cache.freescale.com/files/32bit/doc/data_sheet/IMX28CEC.pdf

This means that the PWM pins may be used to feed a switching circuitry or switching regulator to provide the 5V required by the USB-Host. However, we do not have an application note or example of this implementation.

I apologize for the confusion.

[gordanmarkus]

Thank you for your answer. After doing some research on my own I've came to the same conclusion. This is highly unfortunate.

Regards,

Gordan Markuš