usb: dwc3: gadget: Disable CSP for stream OUT ep

[Felipe Balbi <balbi@kernel.org>]

Tejas Joglekar <tejas.joglekar@synopsys.com> writes:

> In stream mode, when fast-forwarding TRBs, the stream number
> is not cleared causing the new stream to not get assigned. So
> we don't want controller to carry on transfers when short packet
> is received. So disable the CSP for stream capable endpoint.
>
> This is based on the 3.30a Programming guide, where table 3-1
> device descriptor structure field definitions says for CSP bit
> If this bit is 0, the controller generates an XferComplete event
> and remove the stream. So if we keep CSP as 1 then switching between
> streams would not happen as in stream mode, when fast-forwarding
> TRBs, the stream number is not cleared causing the new stream to not get
> assigned.
>
> Signed-off-by: Tejas Joglekar <joglekar@synopsys.com>
> ---
>  drivers/usb/dwc3/gadget.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index f1089ec..0d2afc1 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -986,9 +986,15 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
>  				usb_endpoint_type(dep->endpoint.desc));
>  	}
>  
> -	/* always enable Continue on Short Packet */
> +	/*
> +	 * Enable Continue on Short Packet
> +	 * when endpoint is not a stream capable
> +	 */
>  	if (usb_endpoint_dir_out(dep->endpoint.desc)) {
> -		trb->ctrl |= DWC3_TRB_CTRL_CSP;
> +		if (dep->stream_capable)
> +			trb->ctrl &= ~DWC3_TRB_CTRL_CSP;

Is this necessary? Or would it be enough to have this as:

		if (!dep->stream_capable)
			trb->ctrl |= DWC3_TRB_CTRL_CSP;