[PATCH 2/2] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

[PATCH 2/2] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

[Julius Werner]

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.

Change-Id: Ibf738426307fe8ef362768db2decc9bc2b30a930
Signed-off-by: Julius Werner <jwerner@chromium.org>
---
 drivers/usb/core/config.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 8d72f0c..062967c 100644
--- 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) {
-- 
1.8.3.2

Re: [PATCH 2/2] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

[Greg Kroah-Hartman]

On Tue, Mar 04, 2014 at 10:53:06AM -0800, Julius Werner wrote:
> 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.
> 
> Change-Id: Ibf738426307fe8ef362768db2decc9bc2b30a930

What am I supposed to do with this line?  :)

Re: [PATCH 2/2] usb: Make DELAY_INIT quirk wait 100ms between Get Configuration requests

[Julius Werner]

> What am I supposed to do with this line?  :)
>

Oh damn, sorry, forgot to take that out on the second one. We have
this really annoying commit hook that adds them automatically. v2
incoming...