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SubjectRe: [PATCH] usb: Increase quirk delay for USB devices
On Tue, Sep 05, 2017 at 11:40:56AM +0300, Dmitry Fleytman wrote:
> Commit e0429362ab15
> ("usb: Add device quirk for Logitech HD Pro Webcams C920 and C930e")
> introduced quirk to workaround an issue with some Logitech webcams.
>
> The workaround is introducing delay for some USB operations.
>
> According to our testing, delay introduced by original commit
> is not long enough and in rare cases we still see issues described
> by the aforementioned commit.
>
> This patch increases delays introduced by original commit.
> Having this patch applied we do not see those problems anymore.
>
> Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>
> ---
> drivers/usb/core/config.c | 2 +-
> drivers/usb/core/hub.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 4be52c6..854c8d6 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -852,7 +852,7 @@ int usb_get_configuration(struct usb_device *dev)
> }
>
> if (dev->quirks & USB_QUIRK_DELAY_INIT)
> - msleep(100);
> + msleep(200);

How did you determine the new delays ? Was it discussed with the vendor,
or is it based on trial and error ?

Either case, did you confirm that you need to increase both delays
for the problem to disappear ?

Thanks,
Guenter

>
> result = usb_get_descriptor(dev, USB_DT_CONFIG, cfgno,
> bigbuffer, length);
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 822f8c5..78c2aca 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -4825,7 +4825,7 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
> goto loop;
>
> if (udev->quirks & USB_QUIRK_DELAY_INIT)
> - msleep(1000);
> + msleep(2000);
>
> /* consecutive bus-powered hubs aren't reliable; they can
> * violate the voltage drop budget. if the new child has
> --
> 2.7.4
>

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