usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

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@codeaurora.org>

drivers/usb/dwc3/core.c

@@ -1267,6 +1267,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	u8			rx_max_burst_prd;
 	u8			tx_thr_num_pkt_prd;
 	u8			tx_max_burst_prd;
+	u8			tx_fifo_resize_max_num;
 	const char		*usb_psy_name;
 	int			ret;
 
@@ -1282,6 +1283,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	 */
 	hird_threshold = 12;
 
+	tx_fifo_resize_max_num = 6;
+
 	dwc->maximum_speed = usb_get_maximum_speed(dev);
 	dwc->max_ssp_rate = usb_get_maximum_ssp_rate(dev);
 	dwc->dr_mode = usb_get_dr_mode(dev);
@@ -1325,6 +1328,10 @@ 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->do_fifo_resize = device_property_read_bool(dev,
+							"tx-fifo-resize");
+	device_property_read_u8(dev, "tx-fifo-max-num",
+				&tx_fifo_resize_max_num);
 
 	dwc->disable_scramble_quirk = device_property_read_bool(dev,
 				"snps,disable_scramble_quirk");
@@ -1390,6 +1397,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	dwc->tx_max_burst_prd = tx_max_burst_prd;
 
 	dwc->imod_interval = 0;
+
+	dwc->tx_fifo_resize_max_num = tx_fifo_resize_max_num;
 }
 
 /* check whether the core supports IMOD */

drivers/usb/dwc3/core.h

@@ -1023,6 +1023,7 @@ struct dwc3_scratchpad_array {
  * @rx_max_burst_prd: max periodic ESS receive burst size
  * @tx_thr_num_pkt_prd: periodic ESS transmit packet count
  * @tx_max_burst_prd: max periodic ESS transmit burst size
+ * @tx_fifo_resize_max_num: max number of fifos allocated during txfifo resize
  * @hsphy_interface: "utmi" or "ulpi"
  * @connected: true when we're connected to a host, false otherwise
  * @delayed_status: true when gadget driver asks for delayed status
@@ -1079,6 +1080,11 @@ struct dwc3_scratchpad_array {
  * @dis_split_quirk: set to disable split boundary.
  * @imod_interval: set the interrupt moderation interval in 250ns
  *			increments or 0 to disable.
+ * @max_cfg_eps: current max number of IN eps used across all USB configs.
+ * @last_fifo_depth: last fifo depth used to determine next fifo ram start
+ *		     address.
+ * @num_ep_resized: carries the current number endpoints which have had its tx
+ *		    fifo resized.
  */
 struct dwc3 {
 	struct work_struct	drd_work;
@@ -1233,6 +1239,7 @@ struct dwc3 {
 	u8			rx_max_burst_prd;
 	u8			tx_thr_num_pkt_prd;
 	u8			tx_max_burst_prd;
+	u8			tx_fifo_resize_max_num;
 
 	const char		*hsphy_interface;
 
@@ -1246,6 +1253,7 @@ struct dwc3 {
 	unsigned		is_utmi_l1_suspend:1;
 	unsigned		is_fpga:1;
 	unsigned		pending_events:1;
+	unsigned		do_fifo_resize:1;
 	unsigned		pullups_connected:1;
 	unsigned		setup_packet_pending:1;
 	unsigned		three_stage_setup:1;
@@ -1281,6 +1289,10 @@ struct dwc3 {
 	unsigned		dis_split_quirk:1;
 
 	u16			imod_interval;
+
+	int			max_cfg_eps;
+	int			last_fifo_depth;
+	int			num_ep_resized;
 };
 
 #define INCRX_BURST_MODE 0
@@ -1512,6 +1524,7 @@ 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; }
@@ -1531,6 +1544,8 @@ 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)

drivers/usb/dwc3/ep0.c

@@ -619,6 +619,8 @@ 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))) {

drivers/usb/dwc3/gadget.c

@@ -631,6 +631,179 @@ 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);
 
+/**
+ * dwc3_gadget_calc_tx_fifo_size - calculates the txfifo size value
+ * @dwc: pointer to the DWC3 context
+ * @nfifos: number of fifos to calculate for
+ *
+ * Calculates the size value based on the equation below:
+ *
+ * fifo_size = mult * ((max_packet + mdwidth)/mdwidth + 1) + 1
+ *
+ * The max packet size is set to 1024, as the txfifo requirements mainly apply
+ * to super speed USB use cases.  However, it is safe to overestimate the fifo
+ * allocations for other scenarios, i.e. high speed USB.
+ */
+static int dwc3_gadget_calc_tx_fifo_size(struct dwc3 *dwc, int mult)
+{
+	int max_packet = 1024;
+	int fifo_size;
+	int mdwidth;
+
+	mdwidth = dwc3_mdwidth(dwc);
+
+	/* MDWIDTH is represented in bits, we need it in bytes */
+	mdwidth >>= 3;
+
+	fifo_size = mult * ((max_packet + mdwidth) / mdwidth) + 1;
+	return fifo_size;
+}
+
+/**
+ * dwc3_gadget_clear_tx_fifo_size - Clears txfifo allocation
+ * @dwc: pointer to the DWC3 context
+ *
+ * Iterates through all the endpoint registers and clears the previous txfifo
+ * allocations.
+ */
+void dwc3_gadget_clear_tx_fifos(struct dwc3 *dwc)
+{
+	struct dwc3_ep *dep;
+	int fifo_depth;
+	int size;
+	int num;
+
+	if (!dwc->do_fifo_resize)
+		return;
+
+	/* Read ep0IN related TXFIFO size */
+	dep = dwc->eps[1];
+	size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(0));
+	if (DWC3_IP_IS(DWC3))
+		fifo_depth = DWC3_GTXFIFOSIZ_TXFDEP(size);
+	else
+		fifo_depth = DWC31_GTXFIFOSIZ_TXFDEP(size);
+
+	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(DWC3) ? 0 :
+			dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(num >> 1)) &
+				   DWC31_GTXFIFOSIZ_TXFRAMNUM;
+
+		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 num_fifos = 1;
+	int fifo;
+	int tmp;
+
+	if (!dwc->do_fifo_resize)
+		return 0;
+
+	/* 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))
+		num_fifos = 3;
+
+	if (dep->endpoint.maxburst > 6 &&
+	    usb_endpoint_xfer_bulk(dep->endpoint.desc) && DWC3_IP_IS(DWC31))
+		num_fifos = dwc->tx_fifo_resize_max_num;
+
+	/* 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;
+	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 = (num_fifos - 1) * fifo;
+	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(DWC3))
+		dwc->last_fifo_depth += DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
+	else
+		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) {
+		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(DWC3))
+			fifo_size = DWC3_GTXFIFOSIZ_TXFDEP(fifo_size);
+		else
+			fifo_size = DWC31_GTXFIFOSIZ_TXFDEP(fifo_size);
+
+		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
@@ -648,6 +821,10 @@ 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;
@@ -2498,6 +2675,7 @@ 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);
@@ -2585,6 +2763,39 @@ static int dwc3_gadget_vbus_draw(struct usb_gadget *g, unsigned int mA)
 	return ret;
 }
 
+static int dwc3_gadget_check_config(struct usb_gadget *g, unsigned long ep_map)
+{
+	struct dwc3 *dwc = gadget_to_dwc(g);
+	unsigned long in_ep_map;
+	int fifo_size = 0;
+	int ram1_depth;
+	int ep_num;
+
+	if (!dwc->do_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,
@@ -2596,6 +2807,7 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
 	.udc_set_ssp_rate	= dwc3_gadget_set_ssp_rate,
 	.get_config_params	= dwc3_gadget_config_params,
 	.vbus_draw		= dwc3_gadget_vbus_draw,
+	.check_config		= dwc3_gadget_check_config,
 };
 
 /* -------------------------------------------------------------------------- */