Re: USB flakes out?

[George N. White III]

On Mon, 18 Nov 2019 at 17:24, [e-mail] 
wrote:
> On 18.11.19 21:46, Tom Horsley wrote:
> ...
> > I have no idea what an EMI is, but that's what starts everything.
>
> I guess it is "electromagnetic interference"

Correct.   From hub.c
https://github.com/torvalds/linux/blob/master/drivers/usb/core/hub.c

/*
* EM interference sometimes causes badly shielded USB devices
* to be shutdown by the hub, this hack enables them again.
* Works at least with mouse driver.
*/
if (!(portstatus & USB_PORT_STAT_ENABLE)&& !connect_change && udev) {
   dev_err(&port_dev->dev, "disabled by hub (EMI?), re-enabling...\n");
   connect_change = 1;
}

USB3 devices can be sources of EMI.

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