Re: [PATCH v2] usb: dwc3: gadget: Refine the logic for resizing Tx FIFOs

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

On Tue, Sep 03, 2024, Akash Kumar wrote:
> The current logic is rigid, setting num_fifos to fixed values:
> 
> 3 for any maxburst greater than 1.
> tx_fifo_resize_max_num for maxburst greater than 6.
> Additionally, it did not differentiate much between bulk and
> isochronous transfers, applying similar logic to both.
> 
> The new logic is more dynamic and tailored to the specific needs of
> bulk and isochronous transfers:
> 
> Bulk Transfers: Ensures that num_fifos is optimized by considering
> both the maxburst value and the maximum allowed number of FIFOs.
> 
> Isochronous Transfers: Ensures that num_fifos is sufficient by
> considering the maxburst value and the maximum packet multiplier.
> 
> This change aims to optimize the allocation of Tx FIFOs for both bulk
> and isochronous endpoints, potentially improving data transfer
> efficiency and overall performance.
> It also enhances support for all use cases, which can be tweaked
> with DT parameters and the endpoint’s maxburst and maxpacket.
> 
> Signed-off-by: Akash Kumar <quic_akakum@quicinc.com>
> ---
> Changes for v2:
> Redefine logic for resizing tx fifos.
> 
> Changes for v1:
> Added additional condition to allocate tx fifo for hs isoc eps,
> keeping the other resize logic same.
> ---
>  drivers/usb/dwc3/gadget.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 89fc690fdf34..49809a931104 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -778,15 +778,12 @@ 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)) ||
> -	    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;
> +	if (usb_endpoint_xfer_bulk(dep->endpoint.desc))
> +		num_fifos = min_t(unsigned int, dep->endpoint.maxburst + 1,
> +				  dwc->tx_fifo_resize_max_num);
> +	if (usb_endpoint_xfer_isoc(dep->endpoint.desc))
> +		num_fifos = max_t(unsigned int, dep->endpoint.maxburst,
> +				  usb_endpoint_maxp_mult(dep->endpoint.desc));

No. Don't mix usb_endpoint_maxp_mult with maxburst like this. Check base
on operating speed. Also, now you're ignoring tx_fifo_resize_max_num for
isoc.

BR,
Thinh