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SubjectRe: [PATCH] usbnet: prevent device rpm suspend in usbnet_probe function
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On Tue, 2016-11-08 at 13:44 -0500, Alan Stern wrote:

> These problems could very well be caused by running at SuperSpeed
> (USB-3) instead of high speed (USB-2).
>
> Is there any way to test what happens when the device is attached to
> the computer by a USB-2 cable? That would prevent it from operating at
> SuperSpeed.
>
> The main point, however, is that the proposed patch doesn't seem to
> address the true problem, which is that the device gets suspended
> between probes. The patch only tries to prevent it from being
> suspended during a probe -- which is already prevented by the USB core.

But why doesn't it fail during normal operation?

I suspect that its firmware requires the altsetting

/* should we change control altsetting on a NCM/MBIM function? */
if (cdc_ncm_select_altsetting(intf) == CDC_NCM_COMM_ALTSETTING_MBIM) {
data_altsetting = CDC_NCM_DATA_ALTSETTING_MBIM;
ret = cdc_mbim_set_ctrlalt(dev, intf, CDC_NCM_COMM_ALTSETTING_MBIM);

to be set before it accepts a suspension.

Regards
Oliver


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