> On 5 Sep 2017, at 23:22 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
>> ---
>> 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 ?
It was based in trial and error.
>
> Either case, did you confirm that you need to increase both delays
> for the problem to disappear ?
Yes, according to testing results on our setups.
Thanks,
Dmitry
>
> 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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