Re: [PATCH v2] usb: dwc3: gadget: Add TxFIFO resizing supports for single port RAM

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

On Mon, Nov 11, 2024, Selvarasu Ganesan wrote:
> The existing implementation of the TxFIFO resizing logic only supports
> scenarios where more than one port RAM is used. However, there is a need
> to resize the TxFIFO in USB2.0-only mode where only a single port RAM is
> available. This commit introduces the necessary changes to support
> TxFIFO resizing in such scenarios.
> 
> Cc: stable@vger.kernel.org # 6.12.x: fad16c82: usb: dwc3: gadget: Refine the logic for resizing Tx FIFOs

You should reword the patch $subject and commit message along the line
of adding missing check for single port ram. For this to qualify for
stable, emphasize that this is a fix for certain platform
configurations. Then add a Fixes tag that can go as far as 9f607a309fbe
("usb: dwc3: Resize TX FIFOs to meet EP bursting requirements")

> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
> ---
> 
> Changes in v2:
>  - Removed the code change that limits the number of FIFOs for bulk EP,
>    as plan to address this issue in a separate patch.
>  - Renamed the variable spram_type to is_single_port_ram for better
>    understanding.
>  - Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/lkml/20241107104040.502-1-selvarasu.g@samsung.com/__;!!A4F2R9G_pg!YvZ4F4z6U6Ba9Z6hgsw4-mLPvm9QBopNIbgMe7WSqj7VCUqf9-JQTSV4RE6OdXCw3hJR9suHcjqVrsRlZ7_3ZXQkbAs$ 
> ---
>  drivers/usb/dwc3/core.h   |  4 +++
>  drivers/usb/dwc3/gadget.c | 54 +++++++++++++++++++++++++++++++++------
>  2 files changed, 50 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index eaa55c0cf62f..8306b39e5c64 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -915,6 +915,7 @@ struct dwc3_hwparams {
>  #define DWC3_MODE(n)		((n) & 0x7)
>  
>  /* HWPARAMS1 */
> +#define DWC3_SPRAM_TYPE(n)	(((n) >> 23) & 1)
>  #define DWC3_NUM_INT(n)		(((n) & (0x3f << 15)) >> 15)
>  
>  /* HWPARAMS3 */
> @@ -925,6 +926,9 @@ struct dwc3_hwparams {
>  #define DWC3_NUM_IN_EPS(p)	(((p)->hwparams3 &		\
>  			(DWC3_NUM_IN_EPS_MASK)) >> 18)
>  
> +/* HWPARAMS6 */
> +#define DWC3_RAM0_DEPTH(n)	(((n) & (0xffff0000)) >> 16)
> +
>  /* HWPARAMS7 */
>  #define DWC3_RAM1_DEPTH(n)	((n) & 0xffff)
>  
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 2fed2aa01407..4f2e063c9091 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -687,6 +687,44 @@ static int dwc3_gadget_calc_tx_fifo_size(struct dwc3 *dwc, int mult)
>  	return fifo_size;
>  }
>  
> +/**
> + * dwc3_gadget_calc_ram_depth - calculates the ram depth for txfifo
> + * @dwc: pointer to the DWC3 context
> + */
> +static int dwc3_gadget_calc_ram_depth(struct dwc3 *dwc)
> +{
> +	int ram_depth;
> +	int fifo_0_start;
> +	bool is_single_port_ram;
> +	int tmp;

Try to list this in reversed christmas tree style when possible. Move
declaration of tmp under the if (is_single_port_ram) scope.

> +
> +	/* Check supporting RAM type by HW */
> +	is_single_port_ram = DWC3_SPRAM_TYPE(dwc->hwparams.hwparams1);
> +
> +	/*
> +	 * If a single port RAM is utilized, then allocate TxFIFOs from
> +	 * RAM0. otherwise, allocate them from RAM1.
> +	 */
> +	ram_depth = is_single_port_ram ? DWC3_RAM0_DEPTH(dwc->hwparams.hwparams6) :
> +			DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
> +

Remove extra new empty line.

> +
> +	/*
> +	 * In a single port RAM configuration, the available RAM is shared
> +	 * between the RX and TX FIFOs. This means that the txfifo can begin
> +	 * at a non-zero address.
> +	 */
> +	if (is_single_port_ram) {
> +		/* Check if TXFIFOs start at non-zero addr */
> +		tmp = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
> +		fifo_0_start = DWC3_GTXFIFOSIZ_TXFSTADDR(tmp);
> +
> +		ram_depth -= (fifo_0_start >> 16);
> +	}
> +
> +	return ram_depth;
> +}
> +
>  /**
>   * dwc3_gadget_clear_tx_fifos - Clears txfifo allocation
>   * @dwc: pointer to the DWC3 context
> @@ -753,7 +791,7 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>  {
>  	struct dwc3 *dwc = dep->dwc;
>  	int fifo_0_start;
> -	int ram1_depth;
> +	int ram_depth;
>  	int fifo_size;
>  	int min_depth;
>  	int num_in_ep;
> @@ -773,7 +811,7 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>  	if (dep->flags & DWC3_EP_TXFIFO_RESIZED)
>  		return 0;
>  
> -	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
> +	ram_depth = dwc3_gadget_calc_ram_depth(dwc);
>  
>  	switch (dwc->gadget->speed) {
>  	case USB_SPEED_SUPER_PLUS:
> @@ -809,7 +847,7 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>  
>  	/* 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;
> +	remaining = ram_depth - min_depth - dwc->last_fifo_depth;
>  	remaining = max_t(int, 0, remaining);
>  	/*
>  	 * We've already reserved 1 FIFO per EP, so check what we can fit in
> @@ -835,9 +873,9 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>  		dwc->last_fifo_depth += DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
>  
>  	/* Check fifo size allocation doesn't exceed available RAM size. */
> -	if (dwc->last_fifo_depth >= ram1_depth) {
> +	if (dwc->last_fifo_depth >= ram_depth) {
>  		dev_err(dwc->dev, "Fifosize(%d) > RAM size(%d) %s depth:%d\n",
> -			dwc->last_fifo_depth, ram1_depth,
> +			dwc->last_fifo_depth, ram_depth,
>  			dep->endpoint.name, fifo_size);
>  		if (DWC3_IP_IS(DWC3))
>  			fifo_size = DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
> @@ -3090,7 +3128,7 @@ static int dwc3_gadget_check_config(struct usb_gadget *g)
>  	struct dwc3 *dwc = gadget_to_dwc(g);
>  	struct usb_ep *ep;
>  	int fifo_size = 0;
> -	int ram1_depth;
> +	int ram_depth;
>  	int ep_num = 0;
>  
>  	if (!dwc->do_fifo_resize)
> @@ -3113,8 +3151,8 @@ static int dwc3_gadget_check_config(struct usb_gadget *g)
>  	fifo_size += dwc->max_cfg_eps;
>  
>  	/* Check if we can fit a single fifo per endpoint */
> -	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
> -	if (fifo_size > ram1_depth)
> +	ram_depth = dwc3_gadget_calc_ram_depth(dwc);
> +	if (fifo_size > ram_depth)
>  		return -ENOMEM;
>  
>  	return 0;
> -- 
> 2.17.1
> 

Other than minor nits, the rest looks fine.

Thanks,
Thinh