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

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Message-ID: <20240828020619.y72uf4vm7cuvsnm5@synopsys.com>
Date: Wed, 28 Aug 2024 02:06:22 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Akash Kumar <quic_akakum@...cinc.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jing Leng
	<jleng@...arella.com>, Felipe Balbi <balbi@...nel.org>,
        Jack Pham
	<quic_jackp@...cinc.com>,
        "kernel@...cinc.com" <kernel@...cinc.com>,
        Wesley
 Cheng <quic_wcheng@...cinc.com>,
        Laurent Pinchart
	<laurent.pinchart@...asonboard.com>,
        Daniel Scally
	<dan.scally@...asonboard.com>,
        Vijayavardhan Vennapusa
	<quic_vvreddy@...cinc.com>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: gadget: Fix TX FIFO size for HS ISOC endpoints

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@...cinc.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);
> 
> 

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

Thanks,
Thinh