1. Remove 5V pulse in OTG VBUS when insmod ehci-hcd.ko
What's the issue
In mx25 3stack board, the sequence to insmod USBOTG driver is
insmod fsl_otg_arc.ko
insmod ehci-hcd.ko
insmod arcotg_udc.ko
insmod g_file_storage file=xxxx
when insmod ehci-hcd.ko, there is a 5V pulse in USB_5V_VBUS_OTG, this pulse will keep about 1 second.
Some customer don’t want this 5V pulse. They hope the output in USB_5V_VBUS_OTG is always 0, until usb disk is inserted to the OTG port.
Why there is a 5V pulse
Above picture is OTG VBUS connection in mx25 3stack schematic
The output of USB_5V_VBUS_OTG is decided by pin USBOTG_PWR, when USBOTG_PWR is low, there is a 5V in USB_5V_VBUS_OTG.
After insmod ehci-hcd.ko, in kernel driver, usb_hcd_fsl_probe() -> usb_add_hcd () and usb_hcd_fsl_probe() -> fsl_platform_set_vbus_power (), bit PORT_POWER of PORTSC1 is set to 1, which will pull pin USBOTG_PWR low, so there is a 5V out in pin USB_5V_VBUS_OTG.
If there is not a mini A cable connected to OTG port, ehci_fsl_drv_suspend will be called, bit PORT_POWER of PORTSC1 is set to 0 to pull USBOTG_PWR high, USB_5V_VBUS_OTG is pulled from 5V to 0. You will see a 5V pulse in USB_5V_VBUS_OTG for about 1 second.
How to remove it
Patch enable_usbotg_pwr_pin_after_host_init.patch can remove the 1 second 5V output. It will postpone the configure of GPIO_A to USBOTG_PWR from otg init to the end of usb_hcd_fsl_probe().
2. If insert USB disk before insmod all the usb dirver, USB disk cannot be recognize.
Patch 0001-Remove-usb-irq-disable-and-low-power-mode-in-fsl_udc.patch can fix the issue
3. If run USBOTG in usb slave mode, not enable the OTG mode, D- is high after insmod the slave driver.
Patch 0001-workaround-for-mx25-mx35-usbotg-auto-resume-issue.patch can fix the issue.
Original Attachment has been moved to: 0001-workaround-for-mx25-mx35-usbotg-auto-resume-issue.patch.txt.zip
Original Attachment has been moved to: enable_usbotg_pwr_pin_after_host_init.patch.txt.zip
Original Attachment has been moved to: 0001-Remove-usb-irq-disable-and-low-power-mode-in-fsl_udc.patch.txt.zip
