usb: dwc3: ep0: handle delayed_status again

Since the re-worked ep0 handling (which uses HW's hints to recognize the ep0
status) we lost the delayed status handling. This is used by the file and mass
storage gadget to gain some extra time so setup its internal status before it
can proceed further requests.
In particular the storage gadget does nothing on USB_REQ_SET_CONFIGURATION but
wakes up a thread which handles the request. If the udc driver continues ep0
handling before the thread did its work then then endpoint is not yet
configured and further requests will fail. Once the gadget is ready, it will
enqueue an empty packet which is used for synchronization.
In order to fix this issue, the patch does the following:
Set ->delayed_status once the delayed_status has been notices and do not
continue on the next XferNotReady event. We will continues ep0 processing once
the gadget enqueued the zero packet for synchronization.

A cleaner approach would be to enforce the gadget to enqueue an empty
(zero) request even for the status phase but this would do for now.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.h

@@ -631,6 +631,7 @@ struct dwc3 {
 	unsigned		ep0_bounced:1;
 	unsigned		ep0_expect_in:1;
 	unsigned		start_config_issued:1;
+	unsigned		delayed_status:1;
 
 	enum dwc3_ep0_next	ep0_next_event;
 	enum dwc3_ep0_state	ep0state;

drivers/usb/dwc3/ep0.c

@@ -48,11 +48,14 @@
 
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
+#include <linux/usb/composite.h>
 
 #include "core.h"
 #include "gadget.h"
 #include "io.h"
 
+static void dwc3_ep0_do_control_status(struct dwc3 *dwc, u32 epnum);
+
 static const char *dwc3_ep0_state_string(enum dwc3_ep0_state state)
 {
 	switch (state) {
@@ -122,6 +125,8 @@ static int dwc3_ep0_start_trans(struct dwc3 *dwc, u8 epnum, dma_addr_t buf_dma,
 static int __dwc3_gadget_ep0_queue(struct dwc3_ep *dep,
 		struct dwc3_request *req)
 {
+	struct dwc3		*dwc = dep->dwc;
+	u32			type;
 	int			ret = 0;
 
 	req->request.actual	= 0;
@@ -140,9 +145,7 @@ static int __dwc3_gadget_ep0_queue(struct dwc3_ep *dep,
 	 * IRQ we were waiting for is long gone.
 	 */
 	if (dep->flags & DWC3_EP_PENDING_REQUEST) {
-		struct dwc3	*dwc = dep->dwc;
 		unsigned	direction;
-		u32		type;
 
 		direction = !!(dep->flags & DWC3_EP0_DIR_IN);
 
@@ -162,6 +165,10 @@ static int __dwc3_gadget_ep0_queue(struct dwc3_ep *dep,
 				req->request.dma, req->request.length, type);
 		dep->flags &= ~(DWC3_EP_PENDING_REQUEST |
 				DWC3_EP0_DIR_IN);
+
+	} else if (dwc->delayed_status && (dwc->ep0state == EP0_STATUS_PHASE)) {
+		dwc->delayed_status = false;
+		dwc3_ep0_do_control_status(dwc, 1);
 	}
 
 	return ret;
@@ -211,6 +218,7 @@ static void dwc3_ep0_stall_and_restart(struct dwc3 *dwc)
 	/* stall is always issued on EP0 */
 	__dwc3_gadget_ep_set_halt(dep, 1);
 	dep->flags = DWC3_EP_ENABLED;
+	dwc->delayed_status = false;
 
 	if (!list_empty(&dep->request_list)) {
 		struct dwc3_request	*req;
@@ -472,8 +480,10 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
 		if (!cfg)
 			dwc->dev_state = DWC3_ADDRESS_STATE;
 		break;
+	default:
+		ret = -EINVAL;
 	}
-	return 0;
+	return ret;
 }
 
 static int dwc3_ep0_std_request(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
@@ -536,6 +546,9 @@ static void dwc3_ep0_inspect_setup(struct dwc3 *dwc,
 	else
 		ret = dwc3_ep0_delegate_req(dwc, ctrl);
 
+	if (ret == USB_GADGET_DELAYED_STATUS)
+		dwc->delayed_status = true;
+
 	if (ret >= 0)
 		return;
 
@@ -801,6 +814,13 @@ static void dwc3_ep0_xfernotready(struct dwc3 *dwc,
 			dwc3_ep0_stall_and_restart(dwc);
 			return;
 		}
+
+		if (dwc->delayed_status) {
+			WARN_ON_ONCE(event->endpoint_number != 1);
+			dev_vdbg(dwc->dev, "Mass Storage delayed status\n");
+			return;
+		}
+
 		dwc3_ep0_do_control_status(dwc, event->endpoint_number);
 	}
 }