usb: dwc3: refactor gadget endpoint count calculation

- DWC_USB3_NUM indicates the number of Device mode single directional
  endpoints, including OUT and IN endpoint 0.

- DWC_USB3_NUM_IN_EPS indicates the maximum number of Device mode IN
  endpoints active at any time, including control endpoint 0.

It's possible to configure RTL such that DWC_USB3_NUM_EPS is equal to
DWC_USB3_NUM_IN_EPS.

dwc3-core calculates the number of OUT endpoints as DWC_USB3_NUM minus
DWC_USB3_NUM_IN_EPS. If RTL has been configured with DWC_USB3_NUM_IN_EPS
equal to DWC_USB3_NUM then dwc3-core will calculate the number of OUT
endpoints as zero.

For example a from dwc3_core_num_eps() shows:
[    1.565000]  /usb0@f01d0000: found 8 IN and 0 OUT endpoints

This patch refactors the endpoint calculation down to one variable
dwc->num_eps taking care to maintain the current mapping of endpoints for
fixed FPGA configurations as described in Table 4-7 of version 2.60a of the
DWC USB3 databook.

The endpoint mapping will then be EP-OUT, EP-IN etc, up to DWC_USB3_NUM.
If DWC_USB3_NUM is odd then OUT will take the extra endpoint.

Suggested-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.c

@@ -397,8 +397,7 @@ static void dwc3_core_num_eps(struct dwc3 *dwc)
 {
 	struct dwc3_hwparams	*parms = &dwc->hwparams;
 
-	dwc->num_in_eps = DWC3_NUM_IN_EPS(parms);
-	dwc->num_out_eps = DWC3_NUM_EPS(parms) - dwc->num_in_eps;
+	dwc->num_eps = DWC3_NUM_EPS(parms);
 }
 
 static void dwc3_cache_hwparams(struct dwc3 *dwc)

drivers/usb/dwc3/core.h

@@ -800,8 +800,7 @@ struct dwc3_scratchpad_array {
  * @u2pel: parameter from Set SEL request.
  * @u1sel: parameter from Set SEL request.
  * @u1pel: parameter from Set SEL request.
- * @num_out_eps: number of out endpoints
- * @num_in_eps: number of in endpoints
+ * @num_eps: number of endpoints
  * @ep0_next_event: hold the next expected event
  * @ep0state: state of endpoint zero
  * @link_state: link state
@@ -961,8 +960,7 @@ struct dwc3 {
 
 	u8			speed;
 
-	u8			num_out_eps;
-	u8			num_in_eps;
+	u8			num_eps;
 
 	struct dwc3_hwparams	hwparams;
 	struct dentry		*root;

drivers/usb/dwc3/debugfs.c

@@ -822,19 +822,8 @@ static void dwc3_debugfs_create_endpoint_dirs(struct dwc3 *dwc,
 {
 	int			i;
 
-	for (i = 0; i < dwc->num_in_eps; i++) {
-		u8		epnum = (i << 1) | 1;
-		struct dwc3_ep	*dep = dwc->eps[epnum];
-
-		if (!dep)
-			continue;
-
-		dwc3_debugfs_create_endpoint_dir(dep, parent);
-	}
-
-	for (i = 0; i < dwc->num_out_eps; i++) {
-		u8		epnum = (i << 1);
-		struct dwc3_ep	*dep = dwc->eps[epnum];
+	for (i = 0; i < dwc->num_eps; i++) {
+		struct dwc3_ep	*dep = dwc->eps[i];
 
 		if (!dep)
 			continue;

drivers/usb/dwc3/gadget.c

@@ -2006,14 +2006,13 @@ static const struct usb_gadget_ops dwc3_gadget_ops = {
 
 /* -------------------------------------------------------------------------- */
 
-static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
-		u8 num, u32 direction)
+static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc, u8 num)
 {
 	struct dwc3_ep			*dep;
-	u8				i;
+	u8				epnum;
 
-	for (i = 0; i < num; i++) {
-		u8 epnum = (i << 1) | (direction ? 1 : 0);
+	for (epnum = 0; epnum < num; epnum++) {
+		bool			direction = epnum & 1;
 
 		dep = kzalloc(sizeof(*dep), GFP_KERNEL);
 		if (!dep)
@@ -2021,12 +2020,12 @@ static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
 
 		dep->dwc = dwc;
 		dep->number = epnum;
-		dep->direction = !!direction;
+		dep->direction = direction;
 		dep->regs = dwc->regs + DWC3_DEP_BASE(epnum);
 		dwc->eps[epnum] = dep;
 
 		snprintf(dep->name, sizeof(dep->name), "ep%d%s", epnum >> 1,
-				(epnum & 1) ? "in" : "out");
+				direction ? "in" : "out");
 
 		dep->endpoint.name = dep->name;
 
@@ -2053,7 +2052,7 @@ static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
 			/* MDWIDTH is represented in bits, we need it in bytes */
 			mdwidth /= 8;
 
-			size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(i));
+			size = dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(epnum >> 1));
 			size = DWC3_GTXFIFOSIZ_TXFDEF(size);
 
 			/* FIFO Depth is in MDWDITH bytes. Multiply */
@@ -2103,7 +2102,7 @@ static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
 			dep->endpoint.caps.type_int = true;
 		}
 
-		dep->endpoint.caps.dir_in = !!direction;
+		dep->endpoint.caps.dir_in = direction;
 		dep->endpoint.caps.dir_out = !direction;
 
 		INIT_LIST_HEAD(&dep->pending_list);
@@ -2115,23 +2114,9 @@ static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
 
 static int dwc3_gadget_init_endpoints(struct dwc3 *dwc)
 {
-	int				ret;
-
 	INIT_LIST_HEAD(&dwc->gadget.ep_list);
 
-	ret = dwc3_gadget_init_hw_endpoints(dwc, dwc->num_out_eps, 0);
-	if (ret < 0) {
-		dev_err(dwc->dev, "failed to initialize OUT endpoints\n");
-		return ret;
-	}
-
-	ret = dwc3_gadget_init_hw_endpoints(dwc, dwc->num_in_eps, 1);
-	if (ret < 0) {
-		dev_err(dwc->dev, "failed to initialize IN endpoints\n");
-		return ret;
-	}
-
-	return 0;
+	return dwc3_gadget_init_hw_endpoints(dwc, dwc->num_eps);
 }
 
 static void dwc3_gadget_free_endpoints(struct dwc3 *dwc)