Re: [PATCH v6 3/4] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

From: Thinh Nguyen
Date: Fri Jan 22 2021 - 19:18:00 EST

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In reply to: Bjorn Andersson: "Re: [PATCH v6 3/4] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements"
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Hi,

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.
>
> By introducing the check_config() callback, the resizing logic can fetch
> the maximum number of endpoints used in the USB composition (can contain
> multiple configurations), which helps ensure that the resizing logic can
> fulfill the configuration(s), or return an error to the gadget layer
> otherwise during bind time.
>
> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
> ---
> drivers/usb/dwc3/core.c | 2 +
> drivers/usb/dwc3/core.h | 8 ++
> drivers/usb/dwc3/ep0.c | 2 +
> drivers/usb/dwc3/gadget.c | 194 ++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 206 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 6969196..e7fa6af 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1284,6 +1284,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
> &tx_thr_num_pkt_prd);
> device_property_read_u8(dev, "snps,tx-max-burst-prd",
> &tx_max_burst_prd);
> + dwc->needs_fifo_resize = device_property_read_bool(dev,
> + "tx-fifo-resize");
>
> dwc->disable_scramble_quirk = device_property_read_bool(dev,
> "snps,disable_scramble_quirk");
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index eec1cf4..983b2fd4 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1223,6 +1223,7 @@ struct dwc3 {
> unsigned is_utmi_l1_suspend:1;
> unsigned is_fpga:1;
> unsigned pending_events:1;
> + unsigned needs_fifo_resize:1;

The prefix "need" sounds like a requirement, but I don't think it is the
case here. I think "do" would be a better prefix here.

> unsigned pullups_connected:1;
> unsigned setup_packet_pending:1;
> unsigned three_stage_setup:1;
> @@ -1257,6 +1258,10 @@ struct dwc3 {
> unsigned dis_split_quirk:1;
>
> u16 imod_interval;
> +
> + int max_cfg_eps;
> + int last_fifo_depth;
> + int num_ep_resized;
> };

Please document these new fields.

>
> #define INCRX_BURST_MODE 0
> @@ -1471,6 +1476,7 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd,
> struct dwc3_gadget_ep_cmd_params *params);
> int dwc3_send_gadget_generic_command(struct dwc3 *dwc, unsigned int cmd,
> u32 param);
> +void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc);
> #else
> static inline int dwc3_gadget_init(struct dwc3 *dwc)
> { return 0; }
> @@ -1490,6 +1496,8 @@ static inline int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd,
> static inline int dwc3_send_gadget_generic_command(struct dwc3 *dwc,
> int cmd, u32 param)
> { return 0; }
> +static inline void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc)
> +{ }
> #endif
>
> #if IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
> index 8b668ef..4f216bd 100644
> --- a/drivers/usb/dwc3/ep0.c
> +++ b/drivers/usb/dwc3/ep0.c
> @@ -616,6 +616,8 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
> return -EINVAL;
>
> case USB_STATE_ADDRESS:
> + dwc3_gadget_clear_tx_fifos(dwc);
> +
> ret = dwc3_ep0_delegate_req(dwc, ctrl);
> /* if the cfg matches and the cfg is non zero */
> if (cfg && (!ret || (ret == USB_GADGET_DELAYED_STATUS))) {
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 86f257f..26f9d64 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -615,6 +615,161 @@ static int dwc3_gadget_set_ep_config(struct dwc3_ep *dep, unsigned int action)
> static void dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force,
> bool interrupt);
>
> +static int dwc3_gadget_calc_tx_fifo_size(struct dwc3 *dwc, int mult)

Can you document what this function does?

> +{
> + int max_packet = 1024;

Maybe you can also document why you chose 1024 (e.g. applicable to
Enhanced SuperSpeed only?).

> + int fifo_size;
> + int mdwidth;
> +
> + mdwidth = DWC3_MDWIDTH(dwc->hwparams.hwparams0);
> + /* MDWIDTH is represented in bits, we need it in bytes */
> + mdwidth >>= 3;

mdwidth for DWC32 requires to read hwparams6 for the upper 2 significant
bits. Can we add a check for DWC32 also? You can check how we're doing
it now in the current code.

> +
> + fifo_size = mult * ((max_packet + mdwidth) / mdwidth) + 1;
> + return fifo_size;
> +}
> +
> +void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc)
> +{
> + struct dwc3_ep *dep;
> + int fifo_depth;
> + int size;
> + int num;
> +
> + if (!dwc->needs_fifo_resize)
> + return;
> +
> + /* Read ep0IN related TXFIFO size */
> + dep = dwc->eps[1];
> + size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
> + if (DWC3_IP_IS(DWC31))
> + fifo_depth = DWC31_GTXFIFOSIZ_TXFDEP(size);
> + else
> + fifo_depth = DWC3_GTXFIFOSIZ_TXFDEP(size);

The driver handles 3 IPs. Getting the fifo depth for DWC32 is the same
as DWC31. So the condition should be
if (DWC3_IP_IS(DWC3))
       fifo_depth = ...
else
      fifo_depth = ...

> +
> + dwc->last_fifo_depth = fifo_depth;
> + /* Clear existing TXFIFO for all IN eps except ep0 */
> + for (num = 3; num < min_t(int, dwc->num_eps, DWC3_ENDPOINTS_NUM);
> + num += 2) {
> + dep = dwc->eps[num];
> + /* Don't change TXFRAMNUM on usb31 version */
> + size = DWC3_IP_IS(DWC31) ?
> + dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(num >> 1)) &
> + DWC31_GTXFIFOSIZ_TXFRAMNUM : 0;
> +

Same here. Check for DWC32.

> + dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(num >> 1), size);
> + }
> + dwc->num_ep_resized = 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_ep *dep)
> +{
> + struct dwc3 *dwc = dep->dwc;
> + int fifo_0_start;
> + int ram1_depth;
> + int fifo_size;
> + int min_depth;
> + int num_in_ep;
> + int remaining;
> + int mult = 1;
> + int fifo;
> + int tmp;
> +
> + if (!dwc->needs_fifo_resize)
> + return 0;

Maybe add a condition to check for Enhanced SuperSpeed only?

> +
> + /* resize IN endpoints except ep0 */
> + if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1)
> + return 0;
> +
> + 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))
> + mult = 3;
> +
> + if (dep->endpoint.maxburst > 6 &&
> + usb_endpoint_xfer_bulk(dep->endpoint.desc) && DWC3_IP_IS(DWC31))
> + mult = 6;

You checked maxburst > 1 for isoc, but not when maxburst > 6. Why?
Also, "mult" is the term we usually use for isoc endpoints. Applying it
to bulk is confusing here.

How did we decide on 3 and 6? Are they arbitrary?

> +
> + /* FIFO size for a single buffer */
> + fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
> +
> + /* Calculate the number of remaining EPs w/o any FIFO */
> + num_in_ep = dwc->max_cfg_eps;
> + num_in_ep -= dwc->num_ep_resized;
> +
> + /* 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;

Can "remaining" be a negative value? If so, I think it's clearer if you do
remaining = max_t(int, 0, remaining);

> +
> + /*
> + * 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;

Then use this condition instead:

if (remaining < fifo_size)
       fifo_size = remaining;

> + }
> +
> + fifo_size += fifo;
> + /* Last increment according to the TX FIFO size equation */
> + 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_IP_IS(DWC31))
> + dwc->last_fifo_depth += DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
> + else
> + dwc->last_fifo_depth += DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);

Take account of DWC32.

> +
> + /* 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, ram1_depth,
> + dep->endpoint.name, fifo_size);
> + if (DWC3_IP_IS(DWC31))
> + fifo_size = DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
> + else
> + fifo_size = DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);

Same here.

> + dwc->last_fifo_depth -= fifo_size;
> + return -ENOMEM;
> + }
> +
> + dwc3_writel(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1), fifo_size);
> + dwc->num_ep_resized++;
> +
> + return 0;
> +}
> +
> /**
> * __dwc3_gadget_ep_enable - initializes a hw endpoint
> * @dep: endpoint to be initialized
> @@ -632,6 +787,10 @@ 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(dep);
> + if (ret)
> + return ret;
> +
> ret = dwc3_gadget_start_config(dep);
> if (ret)
> return ret;
> @@ -2418,6 +2577,7 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>
> spin_lock_irqsave(&dwc->lock, flags);
> dwc->gadget_driver = NULL;
> + dwc->max_cfg_eps = 0;
> spin_unlock_irqrestore(&dwc->lock, flags);
>
> free_irq(dwc->irq_gadget, dwc->ev_buf);
> @@ -2485,6 +2645,39 @@ static int dwc3_gadget_vbus_draw(struct usb_gadget *g, unsigned int mA)
> return 0;
> }
>
> +static int dwc3_gadget_check_config(struct usb_gadget *g, unsigned long ep_map)

What's in ep_map? Can you document more to help with the review?

Thanks,
Thinh

> +{
> + struct dwc3 *dwc = gadget_to_dwc(g);
> + unsigned long in_ep_map;
> + int fifo_size = 0;
> + int ram1_depth;
> + int ep_num;
> +
> + if (!dwc->needs_fifo_resize)
> + return 0;
> +
> + /* Only interested in the IN endpoints */
> + in_ep_map = ep_map >> 16;
> + ep_num = hweight_long(in_ep_map);
> +
> + if (ep_num <= dwc->max_cfg_eps)
> + return 0;
> +
> + /* Update the max number of eps in the composition */
> + dwc->max_cfg_eps = ep_num;
> +
> + fifo_size = dwc3_gadget_calc_tx_fifo_size(dwc, dwc->max_cfg_eps);
> + /* Based on the equation, increment by one for every ep */
> + 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)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> static const struct usb_gadget_ops dwc3_gadget_ops = {
> .get_frame = dwc3_gadget_get_frame,
> .wakeup = dwc3_gadget_wakeup,
> @@ -2495,6 +2688,7 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
> .udc_set_speed = dwc3_gadget_set_speed,
> .get_config_params = dwc3_gadget_config_params,
> .vbus_draw = dwc3_gadget_vbus_draw,
> + .check_config = dwc3_gadget_check_config,
> };
>
> /* -------------------------------------------------------------------------- */

Next message: Daniel Latypov: "[PATCH] kunit: make kunit_tool accept optional path to .kunitconfig fragment"
Previous message: Ben Widawsky: "Re: [RFC PATCH v3 15/16] cxl/mem: Add limited Get Log command (0401h)"
In reply to: Bjorn Andersson: "Re: [PATCH v6 3/4] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]