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 <redacted>
---
 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;

 	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;
 };

 
 #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)

+		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)

+{
+	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,
 };
 
 /* -------------------------------------------------------------------------- */