STM32F7 HS + HOST + HUB = infinite OTG_HS IRQs

[maximevince]

I configured my tinyUSB example project like this:

• HOST, HS, HUB, FreeRTOS
• STM32F7 w/ DWC2 USB core
  Whenever I connect a USB HUB, it enumerates the hub, then hogs the system by continously triggering infinite OTG_HS IRQs, like this:
  

Whereas this would be normal looking IRQs at 125us (1 HS microframe) bInterval (no HUB connected, just a regular HID device):

Any idea what's going on - where to look?

[maximevince]

It seems to have to do with const bool more_sof = handle_sof_irq(rhport, in_isr); / more_irq in hcd_dwc2.c, which keeps the ISR from clearing the SOF bit, whenever a HUB is connected. Clearing SOF in all cases works for some use-cases, but seems to break others. (It's obviously not the right solution, but gives a clue).

[maximevince]

It seems like the SOF flag is just not being cleared in the status register.

This fix works for me:

  if (gintsts & GINTSTS_SOF) {
    dwc2->gintsts = GINTSTS_SOF; // ADDED -- Clears the SOF interrupt flag
    const bool more_sof = handle_sof_irq(rhport, in_isr);
    if (!more_sof) {
      dwc2->gintmsk &= ~GINTSTS_SOF;
    }
  }

I'll do some more testing and send a PR if it all works.

[maximevince]

PR is here: #3063

[maximevince]

Fix has been merged