AM4378: USB_DRVVBUS in GPIO mode

Hitoshi Sugawara

Part Number: AM4378
Other Parts Discussed in Thread: AM4372

Hi Experts,

Let me clarify the reason why t is not recommended to configure DRVVBUS pin in GPIO mode to control USB VBUS.

This has been supported by the thread below.

Thank you so much for your the reason.
Best regards,
Hitoshi

over 4 years ago

0 Bin Liu over 4 years ago

TI__Guru*** 125366 points

Hi Hitoshi-san,

When the DRVVBUS pin is not in GPIO mode, the pin is automatically operated by the USB controller to control USB VBUS power switch based on the USB dual-role logic. This capability is lost when DRVVBUS pin is in GPIO mode, plus the Linux or RTOS Processor SDK released by TI won't work if this pin mode is changed.

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

Sorry to interrupt you,

What is the reason why DRVVBUS control based on “USB dual-role logic” is necessary when using USB only as a host mode?

Best regards,

mizutani

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

The USB controller on AM4378 is a dual-role controller, the software has to tell the controller to work in either host or peripheral mode based on certain conditions/configurations. So even if the board configures USB to only work in host mode, the software has to tell the controller to work in host mode, and the controller will control the DRVVBUS pin. The software doesn't directly control the DRVVBUS pin. So please don't configure the pin to GPIO mode for usb use.

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

thank you for your answer.

I want to control VBUS in order to reset the USB device while it is connected.

Is it possible to turn USB_DRVVBUS ON / OFF from userland?

Best regards,

mizutani

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi Mizutani-san,

Neither Processor SDK (Linux or RTOS) uses USB_DRVVBUS pin in GPIO mode to control USB VBUS power, so out of the box, the software won't work.

It sounds like you use Linux? You can unbind/bind the xHCI driver, which will turn on/off USB_DRVVBUS, maybe this is what you need.

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

I use Linux-RT SDK.

Also I modified that the function setting of the USB_DRVVBUS pin as follows.

usb2_pins: usb2_pins {
pinctrl-single,pins = <
AM4372_IOPAD(0xac4, PIN_OUTPUT | MUX_MODE0 ) /* (F25) USB1_DRVVBUS.USB1_DRVVBUS */
>;
};

&usb2 {
dr_mode = "host";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&usb2_pins>;
};

I tried usb unbind with below command.

"echo -n "xhci-hcd.3.auto" > /sys/bus/platform/drivers/xhci-hcd/bind"
or
"echo -n "1-1" > /sys/bus/usb/drivers/usb/unbind"

However, usb vbus (5V) will continue to be supplied.

Is the xHCI driver not unbind with the above command?

Best regards,

mizutani

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi,

I can reproduce the same. Let me look into it and get back to you.

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi,

I am still working on it, and will update once I have a solution.

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

Do you have any update on this issue?

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi,

Sorry for the delay, but I don't have a solution yet. I am working with the hardware designer to understand how to de-assert the USB_DRVVBUS pin. I will keep you posted.

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi,

Please apply the kernel patch in the link below and let me know if it solve the issue.

https://marc.info/?l=linux-usb&m=157365438603161&w=2

0 Bin Liu over 4 years ago

TI__Guru*** 125366 points

Forgot to mention you use the following command to control DRVBUS:

modprobe -r dwc3-omap

modprobe dwc3-omap

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

I modified the DWC3 driver as per your instructions.

However, because I using the Linux version (4.9.59) , there was no dwc3_set_prtcap function.
Therefore, I added the following to the source code and tested it, but usb vbus (5V) will continue to be supplied.

static void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
{
	u32 reg;

	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
	reg &= ~(DWC3_GCTL_PRTCAPDIR(DWC3_GCTL_PRTCAP_OTG));
	reg |= DWC3_GCTL_PRTCAPDIR(mode);
	dwc3_writel(dwc->regs, DWC3_GCTL, reg);
}

Best regards,

mizutani

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

I modified the DWC3 driver as per your instructions.

static void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
{
u32 reg;

reg = dwc3_readl(dwc->regs, DWC3_GCTL);
reg &= ~(DWC3_GCTL_PRTCAPDIR(DWC3_GCTL_PRTCAP_OTG));
reg |= DWC3_GCTL_PRTCAPDIR(mode);
dwc3_writel(dwc->regs, DWC3_GCTL, reg);
}

Best regards,

mizutani

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi Mizutani-san,

In kernel v4.9.59, the function is called dwc3_set_mode(). So please use the following patch instead in your kernel.

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 93a5027f6d52..1b4a5575a008 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1571,6 +1571,7 @@ static void dwc3_core_exit_mode(struct dwc3 *dwc)
                break;
        case USB_DR_MODE_HOST:
                dwc3_host_exit(dwc);
+               dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_DEVICE);
                break;
        case USB_DR_MODE_OTG:
                dwc3_drd_exit(dwc);

0 user4852186 over 4 years ago in reply to Bin Liu

Prodigy 210 points

HI Bin,

Problem has been solved.
Thanks for your cooperation.

Best regards,

mizutani

0 Bin Liu over 4 years ago in reply to user4852186

TI__Guru*** 125366 points

Hi Mizutani-san,

Thanks for the update. Glad the issue is solved. Please kindly click the "This resolved my issue" button if my response answered your question.

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AM4378: USB_DRVVBUS in GPIO mode