[PATCH v3 2/3] usb: dwc3: make role-switching work with debugfs/mode

[Roger Quadros <rogerq@ti.com>]

If dr_mode == "otg", we start by default in PERIPHERAL mode.
Keep track of current role in "current_dr_role" whenever dwc3_set_mode()
is called.

When debugfs/mode is changed AND we're in dual-role mode,
handle the switch by stopping and starting the respective
host/gadget controllers.

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
 drivers/usb/dwc3/core.c    | 21 +++++++++++---------
 drivers/usb/dwc3/core.h    |  3 +++
 drivers/usb/dwc3/debugfs.c | 49 +++++++++++++++++++++++++++++++++++++++-------
 3 files changed, 57 insertions(+), 16 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 369bab1..bf917c2 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -108,6 +108,8 @@ void dwc3_set_mode(struct dwc3 *dwc, u32 mode)
 	reg &= ~(DWC3_GCTL_PRTCAPDIR(DWC3_GCTL_PRTCAP_OTG));
 	reg |= DWC3_GCTL_PRTCAPDIR(mode);
 	dwc3_writel(dwc->regs, DWC3_GCTL, reg);
+
+	dwc->current_dr_role = mode;
 }
 
 u32 dwc3_core_fifo_space(struct dwc3_ep *dep, u8 type)
@@ -277,7 +279,7 @@ static int dwc3_alloc_event_buffers(struct dwc3 *dwc, unsigned length)
  *
  * Returns 0 on success otherwise negative errno.
  */
-static int dwc3_event_buffers_setup(struct dwc3 *dwc)
+int dwc3_event_buffers_setup(struct dwc3 *dwc)
 {
 	struct dwc3_event_buffer	*evt;
 
@@ -862,13 +864,8 @@ static int dwc3_core_init_mode(struct dwc3 *dwc)
 		}
 		break;
 	case USB_DR_MODE_OTG:
-		ret = dwc3_host_init(dwc);
-		if (ret) {
-			if (ret != -EPROBE_DEFER)
-				dev_err(dev, "failed to initialize host\n");
-			return ret;
-		}
-
+		/* start in peripheral role by default */
+		dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_DEVICE);
 		ret = dwc3_gadget_init(dwc);
 		if (ret) {
 			if (ret != -EPROBE_DEFER)
@@ -894,7 +891,13 @@ static void dwc3_core_exit_mode(struct dwc3 *dwc)
 		dwc3_host_exit(dwc);
 		break;
 	case USB_DR_MODE_OTG:
-		dwc3_host_exit(dwc);
+		/* role might have changed since start */
+		if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_HOST) {
+			dwc3_host_exit(dwc);
+			/* Add back UDC to match dwc3_gadget_exit() */
+			usb_add_gadget_udc(dwc->dev, &dwc->gadget);
+		}
+
 		dwc3_gadget_exit(dwc);
 		break;
 	default:
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 7ffdee5..adb04af 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -785,6 +785,7 @@ struct dwc3_scratchpad_array {
  * @maximum_speed: maximum speed requested (mainly for testing purposes)
  * @revision: revision register contents
  * @dr_mode: requested mode of operation
+ * @current_dr_role: current role of operation when in dual-role mode
  * @hsphy_mode: UTMI phy mode, one of following:
  *		- USBPHY_INTERFACE_MODE_UTMI
  *		- USBPHY_INTERFACE_MODE_UTMIW
@@ -901,6 +902,7 @@ struct dwc3 {
 	size_t			regs_size;
 
 	enum usb_dr_mode	dr_mode;
+	u32			current_dr_role;
 	enum usb_phy_interface	hsphy_mode;
 
 	u32			fladj;
@@ -1167,6 +1169,7 @@ struct dwc3_gadget_ep_cmd_params {
 /* prototypes */
 void dwc3_set_mode(struct dwc3 *dwc, u32 mode);
 u32 dwc3_core_fifo_space(struct dwc3_ep *dep, u8 type);
+int dwc3_event_buffers_setup(struct dwc3 *dwc);
 
 /* check whether we are on the DWC_usb3 core */
 static inline bool dwc3_is_usb3(struct dwc3 *dwc)
diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
index 31926dd..a74a83b 100644
--- a/drivers/usb/dwc3/debugfs.c
+++ b/drivers/usb/dwc3/debugfs.c
@@ -327,19 +327,54 @@ static ssize_t dwc3_mode_write(struct file *file,
 		return -EFAULT;
 
 	if (!strncmp(buf, "host", 4))
-		mode |= DWC3_GCTL_PRTCAP_HOST;
+		mode = DWC3_GCTL_PRTCAP_HOST;
 
 	if (!strncmp(buf, "device", 6))
-		mode |= DWC3_GCTL_PRTCAP_DEVICE;
+		mode = DWC3_GCTL_PRTCAP_DEVICE;
 
 	if (!strncmp(buf, "otg", 3))
-		mode |= DWC3_GCTL_PRTCAP_OTG;
+		mode = DWC3_GCTL_PRTCAP_OTG;
 
-	if (mode) {
-		spin_lock_irqsave(&dwc->lock, flags);
-		dwc3_set_mode(dwc, mode);
-		spin_unlock_irqrestore(&dwc->lock, flags);
+	if (!mode)
+		return -EINVAL;
+
+	if (mode == dwc->current_dr_role)
+		goto exit;
+
+	/* prevent role switching if we're not dual-role */
+	if (dwc->dr_mode != USB_DR_MODE_OTG)
+		return -EINVAL;
+
+	/* stop old role */
+	switch (dwc->current_dr_role) {
+	case DWC3_GCTL_PRTCAP_HOST:
+		dwc3_host_exit(dwc);
+		break;
+	case DWC3_GCTL_PRTCAP_DEVICE:
+		usb_del_gadget_udc(&dwc->gadget);
+		break;
+	default:
+		break;
+	}
+
+	/* switch PRTCAP mode. updates current_dr_role */
+	spin_lock_irqsave(&dwc->lock, flags);
+	dwc3_set_mode(dwc, mode);
+	spin_unlock_irqrestore(&dwc->lock, flags);
+
+	/* start new role */
+	switch (dwc->current_dr_role) {
+	case DWC3_GCTL_PRTCAP_HOST:
+		dwc3_host_init(dwc);
+		break;
+	case DWC3_GCTL_PRTCAP_DEVICE:
+		dwc3_event_buffers_setup(dwc);
+		usb_add_gadget_udc(dwc->dev, &dwc->gadget);
+		break;
+	default:
+		break;
 	}
+exit:
 	return count;
 }
 
-- 
2.7.4