Re: usb: dwc2: Detecting cable disconnection in OTG mode?

[Pavel Hofman <pavel.hofman@ivitera.com>]

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

Thanks a lot,

Pavel.