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

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

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@quicinc.com>
> ---
>  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);


Thanks,
Thinh