Hi, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: >> > You're using a really old kernel. Please try with v4.19.11 or v4.20-rc7 >> > >> >> I have to use an altera patched kernel linux-socfpga to boot my board, >> and it always lags behind mainline kernel. If I really had to, I can >> probably backport an individual driver (I already backported dwc2 from >> 4.17). Anyways, in principal is this a bug in dwc2 or libcomposite? >> That is, is libcomposite correct in assuming the dwc2 should call the >> gadget "resume" callback when the plug is reinserted? Or should >> libcomposite getting just the gadget "reset" be enough for it to know >> it may need to update the suspended flag? >> >> I played around with my hardware a bit more, and when I suspend/resume >> the gadget from the host over the usb bus (rather than pulling out >> then reinserting the physical cable) it works fine. That is, the dwc2 >> hardware generates a suspend interrupt then later a resume/wakeup >> interrupt which results in the gadget "resume" callback getting >> called. >> >> However, when pulling/reinserting the cable only the suspend interrupt >> is generated. When the cable is reinserted, there is no resume/wakeup >> interrupt (only some usb reset interrupts) and thus the gadget >> "resume" is never called. > > Maybe the problem is not lack of a resume callback but lack of a > disconnect callback. > > When an unplugged cable is plugged in again, it is not a resume event > but rather a connect event -- and the gadget API does not have > callbacks for connect events. > > When a cable is unplugged it initially appears to be a suspend, but > within a few milliseconds the UDC driver should realize what has > actually happened. The disconnect callback should follow close on the > heels of the suspend callback. after a quick glance at dwc2 driver, it seems like Disconnect Interrupt isn't enabled. There's no handling for it. Minas, any comments? -- balbi
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