Re: [PATCH] usb: Increase quirk delay for USB devices

[Dmitry Fleytman]

> On 5 Sep 2017, at 23:22 PM, Guenter Roeck  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 
>> ---
>> 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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Re: [PATCH] usb: Increase quirk delay for USB devices

[Guenter Roeck]

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 
> ---
>  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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