Re: [PATCH] usb: retry reset if a device times out

[Peter Chen <hzpeterchen@gmail.com>]

On Wed, Feb 10, 2016 at 11:33:18AM +0100, Oliver Neukum wrote:
> Some devices I got show an inability to operate right after
> power on if they are already connected. They are beyond recovery
> if the descriptors are requested multiple times. So in case of
> a timeout we rather bail early and reset again. But it must be
> done only on the first loop lest we get into a reset/time out
> spiral that can be overcome with a retry.
> 
> This patch is a rework of a patch that fell through the cracks.
> http://www.spinics.net/lists/linux-usb/msg103263.html
> 
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> CC: stable@vger.kernel.org
> ---
>  drivers/usb/core/hub.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index f912fe6..e4e46f6 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -4496,7 +4496,13 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
>  						r = -EPROTO;
>  					break;
>  				}
> -				if (r == 0)
> +				/*
> +				 * Some devices time out if they are powered on
> +				 * when already connected. They need a second
> +				 * reset. But only on the first attempt,
> +				 * lest we get into a time out/reset loop
> +				 */
> +				if (r == 0  || (r == -ETIMEDOUT && j == 0))
>  					break;
>  			}
>  			udev->descriptor.bMaxPacketSize0 =
> -- 
> 2.1.4
> 

I remembered you agreed with using outer loop counter (i) as the quit
condition.

-- 

Best Regards,
Peter Chen