usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

The DELAY_INIT quirk only reduces the frequency of enumeration failures
with the Logitech HD Pro C920 and C930e webcams, but does not quite
eliminate them. We have found that adding a delay of 100ms between the
first and second Get Configuration request makes the device enumerate
perfectly reliable even after several weeks of extensive testing. The
reasons for that are anyone's guess, but since the DELAY_INIT quirk
already delays enumeration by a whole second, wating for another 10th of
that isn't really a big deal for the one other device that uses it, and
it will resolve the problems with these webcams.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 8d72f0c659377371cc6c481e33458c7d555f3493..062967c90b2a06e66a081f81ab53aabe1a9e37e4 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -717,6 +717,10 @@ int usb_get_configuration(struct usb_device *dev)
                        result = -ENOMEM;
                        goto err;
                }
+
+               if (dev->quirks & USB_QUIRK_DELAY_INIT)
+                       msleep(100);
+
                result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
                    bigbuffer, length);
                if (result < 0) {