RPi 2 FIQ USB Driver Problems

[george.staroselskiy]

@Pedro_Alves1

Hi Pedro!

The problem is relevant only to RPi2. We’ve experienced the same issue on RPi2 as quoted below:

@mikhail.avkhimenia

Well, it’s 99% ready, there is only one thing holding us - unstable work of rt kernel with usb driver on RPi2. The problem is that new RPi’s USB driver uses FIQ and it somehow causes hangs on SMP system under rt preempt, while the standard USB driver doesn’t work on Raspberry Pi 2 at all. I’ve contacted Raspberry Pi Foundation and opened an issue about the standard USB driver, hope we can work something out soon.

That’s why we’re still using an old driver which also had had some issues with RT patch.

@mikhail.avkhimenia has fixed the issue with the old driver we’re stuck using for now, though.

But unfortunately, the issue with the FIQ driver has not been solved yet. We aspire to have this issue go away as well. It’ll be awesome if someone with greater insight into the USB driver internals would take a look.