Dne 11. 12. 21 v 10:59 Pavel Hofman napsal(a):
Dne 11. 12. 21 v 10:55 Pavel Hofman napsal(a):
Hi Minas,
I am trying to find if dwc2 in OTG mode can pass information to gadget
functions that the host has been disconnected. I am testing on RPi4.
In a datasheet for a different dwc2 implementation
https://www.mouser.cn/datasheet/2/196/Infineon-xmc4500_rm_v1.6_2016-UM-v01_06-EN-598157.pdf
- chapter "16.8.3 Device Disconnection" I found:
===========
The device session ends when the USB cable is disconnected or if the
VBUS is switched off by the host.
The device disconnect flow is as follows:
1. When the USB cable is unplugged or when the VBUS is switched off by
the host, the device core triggers GINTSTS.OTGInt [bit 2] interrupt bit
============
I put a printk to core_intr.c:dwc2_handle_otg_intr() which is called
only from handling the OTGInt interrupt
https://elixir.bootlin.com/linux/v5.1.9/source/drivers/usb/dwc2/core_intr.c#L803
. But this method is not called at all when disconnecting the USB
cable on RPi4 in gadget mode.
To add, the method dwc2_hsotg_disconnect is called, but after
reconnecting the cable, as part of the gadget reset when handling reset
interrupts (gintsts & (GINTSTS_USBRST | GINTSTS_RESETDET)) here
https://elixir.bootlin.com/linux/v5.1.9/source/drivers/usb/dwc2/gadget.c#L3653
Maybe the reason for the OTGInt not being thrown at cable disconnect is
the fact that RPi4 most likely does not handle USB_OTG_ID signal. I
asked about USB_OTG_ID wiring on RPi4 at their forum.
Nevertheless it turns out that DWC2 throws Suspend interrupt
GINTSTS_USBSUSP (11) at cable disconnection on the RPi4, and the gadget
composite driver calls suspend hook of struct usb_function. I wonder if
implementing the suspend handler would be a solution for other dwc2
implementations, or if the audio function should implement also some
other handler in order to correctly serve the cable disconnection for
all dwc2 implementations.
Thanks a lot,
Pavel.
