On Thu, 14 Jul 2011, Ming Lei wrote:
> Hi,
>
> On Wed, Jul 13, 2011 at 11:59 PM, Alan Stern <st...@rowland.harvard.edu>
> wrote:
> > On Wed, 13 Jul 2011, Ming Lei wrote:
>
> >> Almost same.
> >
> > Come on. �"Almost same" means they are different. �That difference is
> > clearly the important thing you need to track down.
>
> I didn't say "entirely same" because we can't trace the packets via usbmon
> during system resume, but we can do it during runtime resume.
>
> In fact, except for above, the packets captured from interrupt ep and control
> ep
> are completely same. Also all functions in uvc (rpm, system)resume path
> return
> successfully.
All right; this tends to confirm your guess that the BIOS messes up the
device by resetting it during system resume.
> >> �If I add USB_QUIRK_RESET_RESUME quirk for the device,
> >> the stream data will not be received from the device in runtime pm case,
> >> same with that in system suspend.
> >
> > uvcvideo should be able to reinitialize the device so that it works
> > correctly following a reset. �If the device doesn't work then uvcvideo
> > has a bug in its reset_resume handler.
>
> This also indicates the usb reset during resume does make the uvc device
> broken.
Resetting the device doesn't actually _break_ it -- if it did then the
device would _never_ work because the first thing that usbcore does to
initialize a new device is reset it!
More likely, the reset erases some device setting that uvcvideo
installed while binding. Evidently uvcvideo does not re-install the
setting during reset-resume; this is probably a bug in the driver.
> The below quirk fixes the issue now.
>
> diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
> index 81ce6a8..93c6fa2 100644
> --- a/drivers/usb/core/quirks.c
> +++ b/drivers/usb/core/quirks.c
> @@ -82,6 +82,9 @@ static const struct usb_device_id usb_quirk_list[] = {
> /* Broadcom BCM92035DGROM BT dongle */
> { USB_DEVICE(0x0a5c, 0x2021), .driver_info = USB_QUIRK_RESET_RESUME },
>
> + /* Microdia uvc camera */
> + { USB_DEVICE(0x0c45, 0x6437), .driver_info = USB_QUIRK_RESET_MORPHS },
> +
> /* Action Semiconductor flash disk */
> { USB_DEVICE(0x10d6, 0x2200), .driver_info =
> USB_QUIRK_STRING_FETCH_255 },
It would be better to fix uvcvideo, if you could figure out what it
needs to do differently. This quirk is only a workaround, because the
device doesn't really morph.
Alan Stern
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