Re: [RFC v3 1/3] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

[Jack Pham]

Hi Wesley,

On Wed, May 27, 2020 at 06:46:01PM -0700, Wesley Cheng wrote:
> Some devices have USB compositions which may require multiple endpoints
> that support EP bursting.  HW defined TX FIFO sizes may not always be
> sufficient for these compositions.  By utilizing flexible TX FIFO
> allocation, this allows for endpoints to request the required FIFO depth to
> achieve higher bandwidth.  With some higher bMaxBurst configurations, using
> a larger TX FIFO size results in better TX throughput.
> 
> Ensure that one TX FIFO is reserved for every IN endpoint.  This allows for
> the FIFO logic to prevent running out of FIFO space.
> 
> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
> ---

<snip>

> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 00746c2..9b09528 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -540,6 +540,117 @@ static int dwc3_gadget_start_config(struct dwc3_ep *dep)
>  	return 0;
>  }
>  
> +/*
> + * dwc3_gadget_resize_tx_fifos - reallocate fifo spaces for current use-case
> + * @dwc: pointer to our context structure
> + *
> + * This function will a best effort FIFO allocation in order
> + * to improve FIFO usage and throughput, while still allowing
> + * us to enable as many endpoints as possible.
> + *
> + * Keep in mind that this operation will be highly dependent
> + * on the configured size for RAM1 - which contains TxFifo -,
> + * the amount of endpoints enabled on coreConsultant tool, and
> + * the width of the Master Bus.
> + *
> + * In general, FIFO depths are represented with the following equation:
> + *
> + * fifo_size = mult * ((max_packet + mdwidth)/mdwidth + 1) + 1
> + *
> + * Conversions can be done to the equation to derive the number of packets that
> + * will fit to a particular FIFO size value.
> + */
> +static int dwc3_gadget_resize_tx_fifos(struct dwc3 *dwc, struct dwc3_ep *dep)

The 'dep' param should be sufficient; we can just get 'dwc' from
dep->dwc. That will make it more clear this function operates on each
endpoint that needs resizing.

> +{
> +	int ram1_depth, mdwidth, fifo_0_start, tmp, num_in_ep;
> +	int min_depth, remaining, fifo_size, mult = 1, fifo, max_packet = 1024;
> +
> +	if (!dwc->needs_fifo_resize)
> +		return 0;
> +
> +	/* resize IN endpoints except ep0 */
> +	if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1)
> +		return 0;
> +
> +	/* Don't resize already resized IN endpoint */
> +	if (dep->fifo_depth)
> +		return 0;
> +
> +	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
> +	mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
> +	/* MDWIDTH is represented in bits, we need it in bytes */
> +	mdwidth >>= 3;
> +
> +	if (((dep->endpoint.maxburst > 1) &&
> +			usb_endpoint_xfer_bulk(dep->endpoint.desc))
> +			|| usb_endpoint_xfer_isoc(dep->endpoint.desc))
> +		mult = 3;
> +
> +	if ((dep->endpoint.maxburst > 6) &&
> +			usb_endpoint_xfer_bulk(dep->endpoint.desc)
> +			&& dwc3_is_usb31(dwc))
> +		mult = 6;
> +
> +	/* FIFO size for a single buffer */
> +	fifo = (max_packet + mdwidth)/mdwidth;
> +	fifo++;
> +
> +	/* Calculate the number of remaining EPs w/o any FIFO */
> +	num_in_ep = dwc->num_eps/2;
> +	num_in_ep -= dwc->num_ep_resized;
> +	/* Ignore EP0 IN */
> +	num_in_ep--;
> +
> +	/* Reserve at least one FIFO for the number of IN EPs */
> +	min_depth = num_in_ep * (fifo+1);
> +	remaining = ram1_depth - min_depth - dwc->last_fifo_depth;
> +
> +	/* We've already reserved 1 FIFO per EP, so check what we can fit in
> +	 * addition to it.  If there is not enough remaining space, allocate
> +	 * all the remaining space to the EP.
> +	 */
> +	fifo_size = (mult-1) * fifo;
> +	if (remaining < fifo_size) {
> +		if (remaining > 0)
> +			fifo_size = remaining;
> +		else
> +			fifo_size = 0;
> +	}
> +
> +	fifo_size += fifo;
> +	fifo_size++;
> +	dep->fifo_depth = fifo_size;
> +
> +	/* Check if TXFIFOs start at non-zero addr */
> +	tmp = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
> +	fifo_0_start = DWC3_GTXFIFOSIZ_TXFSTADDR(tmp);
> +
> +	fifo_size |= (fifo_0_start + (dwc->last_fifo_depth << 16));
> +	if (dwc3_is_usb31(dwc))
> +		dwc->last_fifo_depth += DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
> +	else
> +		dwc->last_fifo_depth += DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
> +
> +	/* Check fifo size allocation doesn't exceed available RAM size. */
> +	if (dwc->last_fifo_depth >= ram1_depth) {
> +		dev_err(dwc->dev, "Fifosize(%d) > RAM size(%d) %s depth:%d\n",
> +				(dwc->last_fifo_depth * mdwidth), ram1_depth,
> +				dep->endpoint.name, fifo_size);

Use dev_WARN() here and eliminate the WARN_ON(1) below?

> +		if (dwc3_is_usb31(dwc))
> +			fifo_size = DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
> +		else
> +			fifo_size = DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
> +		dwc->last_fifo_depth -= fifo_size;
> +		dep->fifo_depth = 0;
> +		WARN_ON(1);
> +		return -ENOMEM;
> +	}
> +
> +	dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1), fifo_size);
> +	dwc->num_ep_resized++;
> +	return 0;
> +}
> +
>  static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
>  {
>  	const struct usb_ss_ep_comp_descriptor *comp_desc;
> @@ -620,6 +731,10 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep, unsigned int action)
>  	int			ret;
>  
>  	if (!(dep->flags & DWC3_EP_ENABLED)) {
> +		ret = dwc3_gadget_resize_tx_fifos(dwc, dep);
> +		if (ret)
> +			return ret;
> +
>  		ret = dwc3_gadget_start_config(dep);
>  		if (ret)
>  			return ret;

Jack
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