[PATCH v2 0/2] Allow DWC3 runtime suspend if UDC is unbinded

[PATCH v2 0/2] Allow DWC3 runtime suspend if UDC is unbinded

[Wesley Cheng]

Changes in v2:
 - Modified logic for executing the runtime PM resume.  Using a sychronous get
   call to avoid race conditions.

During the following scenario, the DWC3 runtime suspend routine is blocked as
the connected flag is still true:

1.  Enumerate device w/ host.
2.  Gadget is unbinded
	- echo "" > /sys/kernel/config/usb_gadget/g1/UDC
3.  Disconnect the USB cable (VBUS low)
4.  No dwc3_gadget_disconnect_interrupt() seen (since controller is
   halted from step#1)
5.  Runtime PM autosuspend fails due to "dwc->connected" being true
(cleared in dwc3_gadget_disconnect_interrupt())
6.  Gadget binded
	- echo udc_name > /sys/kernel/config/usb_gadget/g1/UDC
7.  No runtime suspend until cable is plugged in and out

Technically, for device initiated disconnects, there is no active session/link
with the host, so the DWC3 controller should be allowed to go into a low power
state.  Also, we need to now consider when re-binding the UDC,
dwc3_gadget_set_speed() is executed before dwc3_gadget_pullup(), so if the DWC3
controller is suspended/disabled, while accessing the DCFG, that could result in
bus timeouts, etc...  Change the dwc3_gadget_set_speed() to save the speed
being requested, and program it during dwc3_gadget_run_stop(), which is executed
during PM runtime resume.  If not, previous setting will be overridden as we
execute a DWC3 controller reset during PM runtime resume. 

Wesley Cheng (2):
  usb: dwc3: gadget: Allow runtime suspend if UDC unbinded
  usb: dwc3: gadget: Preserve UDC max speed setting

 drivers/usb/dwc3/core.h   |   1 +
 drivers/usb/dwc3/gadget.c | 121 ++++++++++++++++++++++----------------
 2 files changed, 71 insertions(+), 51 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v2 1/2] usb: dwc3: gadget: Allow runtime suspend if UDC unbinded

[Wesley Cheng]

The DWC3 runtime suspend routine checks for the USB connected parameter to
determine if the controller can enter into a low power state.  The
connected state is only set to false after receiving a disconnect event.
However, in the case of a device initiated disconnect (i.e. UDC unbind),
the controller is halted and a disconnect event is never generated.  Set
the connected flag to false if issuing a device initiated disconnect to
allow the controller to be suspended.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
 drivers/usb/dwc3/gadget.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 5d879b7606d5..babf977cadc0 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2012,6 +2012,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 		}
 	}
 
+	/*
+	 * Check the return value for successful resume, or error.  For a
+	 * successful resume, the DWC3 runtime PM resume routine will handle
+	 * the run stop sequence, so avoid duplicate operations here.
+	 */
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (!ret || ret < 0) {
+		pm_runtime_put(dwc->dev);
+		return 0;
+	}
+
 	/*
 	 * Synchronize any pending event handling before executing the controller
 	 * halt routine.
@@ -2050,10 +2061,12 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 			dwc->ev_buf->lpos = (dwc->ev_buf->lpos + count) %
 						dwc->ev_buf->length;
 		}
+		dwc->connected = false;
 	}
 
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
+	pm_runtime_put(dwc->dev);
 
 	return ret;
 }
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v2 2/2] usb: dwc3: gadget: Preserve UDC max speed setting

[Wesley Cheng]

The USB gadget/UDC driver can restrict the DWC3 controller speed using
dwc3_gadget_set_speed().  Store this setting into a variable, in order for
this setting to persist across controller resets due to runtime PM.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
 drivers/usb/dwc3/core.h   |   1 +
 drivers/usb/dwc3/gadget.c | 108 ++++++++++++++++++++------------------
 2 files changed, 58 insertions(+), 51 deletions(-)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 2f04b3e42bf1..390d3deef0ba 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1119,6 +1119,7 @@ struct dwc3 {
 	u32			nr_scratch;
 	u32			u1u2;
 	u32			maximum_speed;
+	u32			gadget_max_speed;
 
 	u32			ip;
 
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index babf977cadc0..c145da1d8ba5 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1941,6 +1941,61 @@ static void dwc3_stop_active_transfers(struct dwc3 *dwc)
 	}
 }
 
+static void __dwc3_gadget_set_speed(struct dwc3 *dwc)
+{
+	u32			reg;
+
+	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
+	reg &= ~(DWC3_DCFG_SPEED_MASK);
+
+	/*
+	 * WORKAROUND: DWC3 revision < 2.20a have an issue
+	 * which would cause metastability state on Run/Stop
+	 * bit if we try to force the IP to USB2-only mode.
+	 *
+	 * Because of that, we cannot configure the IP to any
+	 * speed other than the SuperSpeed
+	 *
+	 * Refers to:
+	 *
+	 * STAR#9000525659: Clock Domain Crossing on DCTL in
+	 * USB 2.0 Mode
+	 */
+	if (DWC3_VER_IS_PRIOR(DWC3, 220A) &&
+	    !dwc->dis_metastability_quirk) {
+		reg |= DWC3_DCFG_SUPERSPEED;
+	} else {
+		switch (dwc->gadget_max_speed) {
+		case USB_SPEED_LOW:
+			reg |= DWC3_DCFG_LOWSPEED;
+			break;
+		case USB_SPEED_FULL:
+			reg |= DWC3_DCFG_FULLSPEED;
+			break;
+		case USB_SPEED_HIGH:
+			reg |= DWC3_DCFG_HIGHSPEED;
+			break;
+		case USB_SPEED_SUPER:
+			reg |= DWC3_DCFG_SUPERSPEED;
+			break;
+		case USB_SPEED_SUPER_PLUS:
+			if (DWC3_IP_IS(DWC3))
+				reg |= DWC3_DCFG_SUPERSPEED;
+			else
+				reg |= DWC3_DCFG_SUPERSPEED_PLUS;
+			break;
+		default:
+			dev_err(dwc->dev, "invalid speed (%d)\n", dwc->gadget_max_speed);
+
+			if (DWC3_IP_IS(DWC3))
+				reg |= DWC3_DCFG_SUPERSPEED;
+			else
+				reg |= DWC3_DCFG_SUPERSPEED_PLUS;
+		}
+	}
+	dwc3_writel(dwc->regs, DWC3_DCFG, reg);
+}
+
 static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 {
 	u32			reg;
@@ -1963,6 +2018,7 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 		if (dwc->has_hibernation)
 			reg |= DWC3_DCTL_KEEP_CONNECT;
 
+		__dwc3_gadget_set_speed(dwc);
 		dwc->pullups_connected = true;
 	} else {
 		reg &= ~DWC3_DCTL_RUN_STOP;
@@ -2325,59 +2381,9 @@ static void dwc3_gadget_set_speed(struct usb_gadget *g,
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
 	unsigned long		flags;
-	u32			reg;
 
 	spin_lock_irqsave(&dwc->lock, flags);
-	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
-	reg &= ~(DWC3_DCFG_SPEED_MASK);
-
-	/*
-	 * WORKAROUND: DWC3 revision < 2.20a have an issue
-	 * which would cause metastability state on Run/Stop
-	 * bit if we try to force the IP to USB2-only mode.
-	 *
-	 * Because of that, we cannot configure the IP to any
-	 * speed other than the SuperSpeed
-	 *
-	 * Refers to:
-	 *
-	 * STAR#9000525659: Clock Domain Crossing on DCTL in
-	 * USB 2.0 Mode
-	 */
-	if (DWC3_VER_IS_PRIOR(DWC3, 220A) &&
-	    !dwc->dis_metastability_quirk) {
-		reg |= DWC3_DCFG_SUPERSPEED;
-	} else {
-		switch (speed) {
-		case USB_SPEED_LOW:
-			reg |= DWC3_DCFG_LOWSPEED;
-			break;
-		case USB_SPEED_FULL:
-			reg |= DWC3_DCFG_FULLSPEED;
-			break;
-		case USB_SPEED_HIGH:
-			reg |= DWC3_DCFG_HIGHSPEED;
-			break;
-		case USB_SPEED_SUPER:
-			reg |= DWC3_DCFG_SUPERSPEED;
-			break;
-		case USB_SPEED_SUPER_PLUS:
-			if (DWC3_IP_IS(DWC3))
-				reg |= DWC3_DCFG_SUPERSPEED;
-			else
-				reg |= DWC3_DCFG_SUPERSPEED_PLUS;
-			break;
-		default:
-			dev_err(dwc->dev, "invalid speed (%d)\n", speed);
-
-			if (DWC3_IP_IS(DWC3))
-				reg |= DWC3_DCFG_SUPERSPEED;
-			else
-				reg |= DWC3_DCFG_SUPERSPEED_PLUS;
-		}
-	}
-	dwc3_writel(dwc->regs, DWC3_DCFG, reg);
-
+	dwc->gadget_max_speed = speed;
 	spin_unlock_irqrestore(&dwc->lock, flags);
 }
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v2 0/2] Allow DWC3 runtime suspend if UDC is unbinded

[Wesley Cheng]

Changes in v2:
 - Modified logic for executing the runtime PM resume.  Using a sychronous get
   call to avoid race conditions.

During the following scenario, the DWC3 runtime suspend routine is blocked as
the connected flag is still true:

1.  Enumerate device w/ host.
2.  Gadget is unbinded
	- echo "" > /sys/kernel/config/usb_gadget/g1/UDC
3.  Disconnect the USB cable (VBUS low)
4.  No dwc3_gadget_disconnect_interrupt() seen (since controller is
   halted from step#1)
5.  Runtime PM autosuspend fails due to "dwc->connected" being true
(cleared in dwc3_gadget_disconnect_interrupt())
6.  Gadget binded
	- echo udc_name > /sys/kernel/config/usb_gadget/g1/UDC
7.  No runtime suspend until cable is plugged in and out

Technically, for device initiated disconnects, there is no active session/link
with the host, so the DWC3 controller should be allowed to go into a low power
state.  Also, we need to now consider when re-binding the UDC,
dwc3_gadget_set_speed() is executed before dwc3_gadget_pullup(), so if the DWC3
controller is suspended/disabled, while accessing the DCFG, that could result in
bus timeouts, etc...  Change the dwc3_gadget_set_speed() to save the speed
being requested, and program it during dwc3_gadget_run_stop(), which is executed
during PM runtime resume.  If not, previous setting will be overridden as we
execute a DWC3 controller reset during PM runtime resume. 

Wesley Cheng (2):
  usb: dwc3: gadget: Allow runtime suspend if UDC unbinded
  usb: dwc3: gadget: Preserve UDC max speed setting

 drivers/usb/dwc3/core.h   |   1 +
 drivers/usb/dwc3/gadget.c | 121 ++++++++++++++++++++++----------------
 2 files changed, 71 insertions(+), 51 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v2 1/2] usb: dwc3: gadget: Allow runtime suspend if UDC unbinded

[Wesley Cheng]

The DWC3 runtime suspend routine checks for the USB connected parameter to
determine if the controller can enter into a low power state.  The
connected state is only set to false after receiving a disconnect event.
However, in the case of a device initiated disconnect (i.e. UDC unbind),
the controller is halted and a disconnect event is never generated.  Set
the connected flag to false if issuing a device initiated disconnect to
allow the controller to be suspended.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
 drivers/usb/dwc3/gadget.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 5d879b7606d5..babf977cadc0 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2012,6 +2012,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 		}
 	}
 
+	/*
+	 * Check the return value for successful resume, or error.  For a
+	 * successful resume, the DWC3 runtime PM resume routine will handle
+	 * the run stop sequence, so avoid duplicate operations here.
+	 */
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (!ret || ret < 0) {
+		pm_runtime_put(dwc->dev);
+		return 0;
+	}
+
 	/*
 	 * Synchronize any pending event handling before executing the controller
 	 * halt routine.
@@ -2050,10 +2061,12 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 			dwc->ev_buf->lpos = (dwc->ev_buf->lpos + count) %
 						dwc->ev_buf->length;
 		}
+		dwc->connected = false;
 	}
 
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
+	pm_runtime_put(dwc->dev);
 
 	return ret;
 }
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project