Re: [PATCH 01/13] usb: define a generic USB_RESUME_TIMEOUT macro

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, Feb 13, 2015 at 03:07:43PM -0600, Felipe Balbi wrote:
> Every USB Host controller should use this new
> macro to define for how long resume signalling
> should be driven on the bus.
> 
> Currently, almost every single USB controller
> is using a 20ms timeout for resume signalling.
> 
> That's problematic for two reasons:
> 
> a) sometimes that 20ms timer expires a little
> before 20ms, which makes us fail certification
> 
> b) some (many) devices actually need more than
> 20ms resume signalling.
> 
> Sure, in case of (b) we can state that the device
> is against the USB spec, but the fact is that
> we have no control over which device the certification
> lab will use. We also have no control over which host
> they will use. Most likely they'll be using a Windows
> PC which, again, we have no control over how that
> USB stack is written and how long resume signalling
> they are using.
> 
> At the end of the day, we must make sure Linux passes
> electrical compliance when working as Host or as Device
> and currently we don't pass compliance as host because
> we're driving resume signallig for exactly 20ms and
> that confuses certification test setup resulting in
> Certification failure.
> 
> Signed-off-by: Felipe Balbi <balbi@xxxxxx>
> ---
>  include/linux/usb.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index f89c24a03bd9..1dd89f0db344 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -210,6 +210,9 @@ void usb_put_intf(struct usb_interface *intf);
>  #define USB_MAXINTERFACES	32
>  #define USB_MAXIADS		(USB_MAXINTERFACES/2)
>  
> +/* USB Resume Timer */
> +#define USB_RESUME_TIMEOUT	40 /* ms */
> +

If you add the comment as Alan suggested, feel free to add:

Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux