On Fri, Sep 02, 2016 at 09:55:52AM +0800, Peter Chen wrote: > Do you have other 5V to USB_H1_VBUS? USB PHY needs 5V input voltage > as the source for USB LDO (3.0v), either from OTG or Host 1. I suspect > the lower vbus voltage causes the USB LDO voltage less than 3.0v, then > cause the unstable for USB PHY. If possible, you can connect MAIN 5V > (if it exists) directly to USB_H1_VBUS to see if this problem is fixed. Yes, USB_H1_VBUS is supplied from internal 5V and it is accurate (+/- 0.03V). The USB_H_EN signal enables USB_H1_VBUS through a MIC2026-1. The USB_OTG_VBUS signal from the picture with 4.69V came from the host PC and is not under our control. I read in the ReferenceManual that the USBPHY defaults to USB_H1_VBUS if both USB_OTG_VBUS and USB_H1_VBUS are available. If we imagine the following situation: USB OTG cable is plugged-in, the board is powered on, USB_OTG_VBUS is supplied externally and USBPHY uses it because USB_H1_EN is not high yet and did not enable USB_H1_VBUS. If the USBPHY started out being supplied by USB_OTG_VBUS and later on, USB_H1_VBUS comes up, will the USBPHY switch to USB_H1_VBUS immediately or stay at being supplied by USB_OTG_VBUS as long as that is available? > Great. Can you see the sudden lower for vbus again? If it still exists, it may > be GND issue. Yes it is still visible. Does not seem to be a problem though. > Avoid NULL pointer deference is necessary. Patch is welcome :) Yes, but should we also stop the gadget driver and print an error message? Or just return from the isr and neither report nor stop? Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
