[U-Boot] [PATCH 2/2] usb: gadget: fastboot: Dequeue the previous IN request for the current request

[Lukasz Majewski]

Hi Paul,

> Recent versions of the fastboot tool will query the partition type
> before doing an operation on a partition (such as erase, flash, etc).
> It will then submit the operation as soon as the response for the
> partition type is received.
> 
> Usually, the MUSB controller will see that the partition type request
> return status was read by the host at the very same time as the
> actual operation request is submitted by the host. However, the
> operation will be read first (int_rx is handled first in
> musb_interrupt) and after it is completed, the fastboot USB gadget
> driver will send another return status. Hence, this happens before
> the musb gadget framework has had a chance to handle the previous
> acknowledgement that the host read the return status and dequeue the
> request.
> 
> The host will then usually empty the FIFO by the time musb_interrupt
> gets around handling the return status acknowledgement (for the
> previous request, this is still on the same musb_interrupt call), so
> no other interrupt is generated and the most recent return status
> acknowledgement remains unaccounted for.
> 
> It will then be used as a response for the next command, and the
> proper response for it will be delayed to the next command, and so on.
> 
> Dequeuing the previous IN request in the fastboot code ensures that
> no previous return status remains. It is acceptable to do it since
> there is no callback to it anyways.
> 
> Signed-off-by: Paul Kocialkowski <contact at paulk.fr>
> ---
>  drivers/usb/gadget/f_fastboot.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/gadget/f_fastboot.c
> b/drivers/usb/gadget/f_fastboot.c index b9a9099..60c846d 100644
> --- a/drivers/usb/gadget/f_fastboot.c
> +++ b/drivers/usb/gadget/f_fastboot.c
> @@ -311,6 +311,9 @@ static int fastboot_tx_write(const char *buffer,
> unsigned int buffer_size) 
>  	memcpy(in_req->buf, buffer, buffer_size);
>  	in_req->length = buffer_size;
> +
> +	usb_ep_dequeue(fastboot_func->in_ep, in_req);
> +
>  	ret = usb_ep_queue(fastboot_func->in_ep, in_req, 0);
>  	if (ret)
>  		printf("Error %d on queue\n", ret);

Reviewed-by: Lukasz Majewski <l.majewski at samsung.com>

Comment the same as for [PATCH 1/2]

-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group