Re: [PATCH] usb: dwc3: gadget: Fix TX FIFO size for HS ISOC endpoints

[Thinh Nguyen]

On Tue, Aug 27, 2024, Thinh Nguyen wrote:
> On Tue, Aug 27, 2024, Akash Kumar wrote:
> > Use 2K TX FIFO size for low-resolution UVC cameras to support the
> > maximum possible UVC instances. Restrict 2K TX FIFO size based on
> > the minimum maxburst required to run low-resolution UVC cameras.
> > 
> > Signed-off-by: Akash Kumar <quic_akakum@xxxxxxxxxxx>
> > ---
> >  drivers/usb/dwc3/gadget.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 89fc690fdf34..f342ccda6705 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -788,6 +788,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
> >  	     usb_endpoint_xfer_isoc(dep->endpoint.desc)) && DWC3_IP_IS(DWC31))
> >  		num_fifos = dwc->tx_fifo_resize_max_num;
> >  
> > +	if (dep->endpoint.maxburst <= 1 &&
> > +	    usb_endpoint_xfer_isoc(dep->endpoint.desc))
> > +		num_fifos = 2;
> > +
> >  	/* FIFO size for a single buffer */
> >  	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
> >  
> > -- 
> > 2.17.1
> > 
> 
> These settings are starting to get too specific for each application.
> Can we find a better calculation?
> 
> Perhaps something like this? (code not tested)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 9a18973ebc05..d54b08f92aea 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -908,15 +908,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>  
>  	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
>  
> -	if ((dep->endpoint.maxburst > 1 &&
> -	     usb_endpoint_xfer_bulk(dep->endpoint.desc)) ||
> +	if (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
>  	    usb_endpoint_xfer_isoc(dep->endpoint.desc))
> -		num_fifos = 3;
> -
> -	if (dep->endpoint.maxburst > 6 &&
> -	    (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
> -	     usb_endpoint_xfer_isoc(dep->endpoint.desc)) && DWC3_IP_IS(DWC31))
> -		num_fifos = dwc->tx_fifo_resize_max_num;
> +		num_fifos = min_t(unsigned int, dep->endpoint.maxburst + 1,
> +				  dwc->tx_fifo_resize_max_num);
>  
>  	/* FIFO size for a single buffer */
>  	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
> 
> 

Also, for highspeed, we don't check maxburst. Check for additional
packets properly.

Thanks,
Thinh