linux-kernel - Re: [PATCH v7] usb: dwc3: gadget: Refine the logic for resizing Tx FIFOs

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Message-ID: <20241018235012.ylaxxyj5zd5j2nbk@synopsys.com>
Date: Fri, 18 Oct 2024 23:50:24 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Akash Kumar <quic_akakum@...cinc.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        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 v7] usb: dwc3: gadget: Refine the logic for resizing Tx
 FIFOs

On Thu, Oct 17, 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 updated logic is more flexible and specifically designed to meet
> the unique requirements of both bulk and isochronous transfers. We
> have made every effort to satisfy all needs and requirements, verified
> on our specific platform and application.
> 
> Bulk Transfers: Ensures that num_fifos is optimized by considering both
> the maxburst and DT property "tx-fifo-max-num" for super speed and
> above. For high-speed and below bulk endpoints, a 2K TxFIFO allocation
> is used to meet efficient data transfer needs, considering
> FIFO-constrained platforms.
> 
> Isochronous Transfers: Ensures that num_fifos is sufficient by
> considering the maximum packet multiplier for HS and below and maxburst
> for Super-speed and above eps, along with a constraint with the DT
> property "tx-fifo-max-num".
> 
> 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. This structured approach ensures that the appropriate number
> of FIFOs is allocated based on the endpoint type and USB speed.
> 
> Signed-off-by: Akash Kumar <quic_akakum@...cinc.com>
> ---
> Changes for v7:
> fixed indentations for if checks.
> 
> Changes for v6:
> The code has been refactored to replace multiple if checks with a
> switch-case structure based on the USB speed. This change improves
> readability and maintainability by clearly defining behavior for
> different USB speeds. This structured approach ensures that the
> appropriate number of FIFOs is allocated based on the endpoint
> type and USB speed.
> 
> Changes for v5:
> Update Calculation for HS and below bulk and isoc eps based on
> suggestion and fixed at 2k for bulk eps considering fifo constrained
> platforms.
> 
> Changes for v4:
> Updated commit message as per review comments to clarify that it has
> been tested on specific platforms only and tried best to match all
> expectations.
> 
> Changes for v3:
> Redefine logic for resizing tx fifos,added check based on  operating
> speed and used maxp for HS and maxburst for SS  and defined max allocation
> based on dt property.
> 
> Changes for v2:
> Redefine logic for resizing tx fifos, handled fifo based on  minimum of
> maxp and maxburts.
> 
> 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 | 33 ++++++++++++++++++++++++---------
>  1 file changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 10178e5eda5a..af3d5b2f7b67 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -771,15 +771,30 @@ 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;
> +	switch (dwc->gadget->speed) {
> +	case USB_SPEED_SUPER_PLUS:
> +	case USB_SPEED_SUPER:
> +		if (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
> +		    usb_endpoint_xfer_isoc(dep->endpoint.desc))
> +			num_fifos = min_t(unsigned int,
> +					  dep->endpoint.maxburst,
> +					  dwc->tx_fifo_resize_max_num);
> +		break;
> +	case USB_SPEED_HIGH:
> +		if (usb_endpoint_xfer_isoc(dep->endpoint.desc)) {
> +			num_fifos = min_t(unsigned int,
> +					  usb_endpoint_maxp_mult(dep->endpoint.desc) + 1,
> +					  dwc->tx_fifo_resize_max_num);
> +			break;
> +		}
> +		fallthrough;
> +	case USB_SPEED_FULL:
> +		if (usb_endpoint_xfer_bulk(dep->endpoint.desc))
> +			num_fifos = 2;
> +		break;
> +	default:
> +		break;
> +	}
>  
>  	/* FIFO size for a single buffer */
>  	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
> -- 
> 2.17.1

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh