usb: mtu3: handle delayed status of the control transfer

Add the delayed status handling. This is used by mass storage etc to
gain some extra time to setup its internal status before it can proceed
further requests, and once the gadget is ready, it will enqueue an
empty packet which is used for synchronization.
The issue may happen on some FGPA platform with very low cpu frequency.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/mtu3/mtu3.h

@@ -288,6 +288,7 @@ static inline struct ssusb_mtk *dev_to_ssusb(struct device *dev)
  *		MTU3_U3_IP_SLOT_DEFAULT for U3 IP
  * @may_wakeup: means device's remote wakeup is enabled
  * @is_self_powered: is reported in device status and the config descriptor
+ * @delayed_status: true when function drivers ask for delayed status
  * @ep0_req: dummy request used while handling standard USB requests
  *		for GET_STATUS and SET_SEL
  * @setup_buf: ep0 response buffer for GET_STATUS and SET_SEL requests
@@ -327,6 +328,7 @@ struct mtu3 {
 	unsigned u1_enable:1;
 	unsigned u2_enable:1;
 	unsigned is_u3_ip:1;
+	unsigned delayed_status:1;
 
 	u8 address;
 	u8 test_mode_nr;

drivers/usb/mtu3/mtu3_gadget.c

@@ -663,6 +663,7 @@ int mtu3_gadget_setup(struct mtu3 *mtu)
 	mtu->g.sg_supported = 0;
 	mtu->g.name = MTU3_DRIVER_NAME;
 	mtu->is_active = 0;
+	mtu->delayed_status = false;
 
 	mtu3_gadget_init_eps(mtu);
 
@@ -727,4 +728,5 @@ void mtu3_gadget_reset(struct mtu3 *mtu)
 	mtu->address = 0;
 	mtu->ep0_state = MU3D_EP0_STATE_SETUP;
 	mtu->may_wakeup = 0;
+	mtu->delayed_status = false;
 }

drivers/usb/mtu3/mtu3_gadget_ep0.c

@@ -16,6 +16,8 @@
  *
  */
 
+#include <linux/usb/composite.h>
+
 #include "mtu3.h"
 
 /* ep0 is always mtu3->in_eps[0] */
@@ -150,6 +152,7 @@ static void ep0_stall_set(struct mtu3_ep *mep0, bool set, u32 pktrdy)
 		csr = (csr & ~EP0_SENDSTALL) | EP0_SENTSTALL;
 	mtu3_writel(mtu->mac_base, U3D_EP0CSR, csr);
 
+	mtu->delayed_status = false;
 	mtu->ep0_state = MU3D_EP0_STATE_SETUP;
 
 	dev_dbg(mtu->dev, "ep0: %s STALL, ep0_state: %s\n",
@@ -656,6 +659,9 @@ stall:
 finish:
 	if (mtu->test_mode) {
 		;	/* nothing to do */
+	} else if (handled == USB_GADGET_DELAYED_STATUS) {
+		/* handle the delay STATUS phase till receive ep_queue on ep0 */
+		mtu->delayed_status = true;
 	} else if (le16_to_cpu(setup.wLength) == 0) { /* no data stage */
 
 		mtu3_writel(mbase, U3D_EP0CSR,
@@ -775,9 +781,6 @@ static int ep0_queue(struct mtu3_ep *mep, struct mtu3_request *mreq)
 	dev_dbg(mtu->dev, "%s %s (ep0_state: %s), len#%d\n", __func__,
 		mep->name, decode_ep0_state(mtu), mreq->request.length);
 
-	if (!list_empty(&mep->req_list))
-		return -EBUSY;
-
 	switch (mtu->ep0_state) {
 	case MU3D_EP0_STATE_SETUP:
 	case MU3D_EP0_STATE_RX:	/* control-OUT data */
@@ -789,6 +792,20 @@ static int ep0_queue(struct mtu3_ep *mep, struct mtu3_request *mreq)
 		return -EINVAL;
 	}
 
+	if (mtu->delayed_status) {
+		u32 csr;
+
+		mtu->delayed_status = false;
+		csr = mtu3_readl(mtu->mac_base, U3D_EP0CSR) & EP0_W1C_BITS;
+		csr |= EP0_SETUPPKTRDY | EP0_DATAEND;
+		mtu3_writel(mtu->mac_base, U3D_EP0CSR, csr);
+		/* needn't giveback the request for handling delay STATUS */
+		return 0;
+	}
+
+	if (!list_empty(&mep->req_list))
+		return -EBUSY;
+
 	list_add_tail(&mreq->list, &mep->req_list);
 
 	/* sequence #1, IN ... start writing the data */