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

[Selvarasu Ganesan <selvarasu.g@samsung.com>]

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
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://lore.kernel.org/lkml/20241107104040.502-1-selvarasu.g@samsung.com/
---
 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;
+
+	/* 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);
+
+
+	/*
+	 * 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