[PATCH v2 4/4] usb: dwc3: gadget: check if dep->frame_number is still valid

[Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>]

Gadget driver may take an unbounded amount of time to queue requests
after XferNotReady. This is important for isochronous endpoints which
need to be started for a specific (micro-)frame.

If we fail to start a transfer for isochronous endpoint, let's try
queueing to a future interval and see if that helps. We will stop trying
if we fail a start transfer for 5 intervals in the future.

Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
---

changes since v1:
	- switch to a retry approach instead of capturing timestamps

 drivers/usb/dwc3/core.h   |  1 +
 drivers/usb/dwc3/gadget.c | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index ea59f9b4908a..85599ad6648f 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -38,6 +38,7 @@
 #define DWC3_EP0_SETUP_SIZE	512
 #define DWC3_ENDPOINTS_NUM	32
 #define DWC3_XHCI_RESOURCES_NUM	2
+#define DWC3_ISOC_MAX_RETRIES	5
 
 #define DWC3_SCRATCHBUF_SIZE	4096	/* each buffer is assumed to be 4KiB */
 #define DWC3_EVENT_BUFFERS_SIZE	4096
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index d8c7ad0c22e8..1590516735cb 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -27,7 +27,7 @@
 #include "gadget.h"
 #include "io.h"
 
-#define DWC3_ALIGN_FRAME(d)	(((d)->frame_number + (d)->interval) \
+#define DWC3_ALIGN_FRAME(d, n)	(((d)->frame_number + ((d)->interval * (n))) \
 					& ~((d)->interval - 1))
 
 /**
@@ -1268,13 +1268,24 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
 
 static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 {
+	int retries;
+	int ret;
+	int i;
+
 	if (list_empty(&dep->pending_list)) {
 		dep->flags |= DWC3_EP_PENDING_REQUEST;
 		return -EAGAIN;
 	}
 
-	dep->frame_number = DWC3_ALIGN_FRAME(dep);
-	return __dwc3_gadget_kick_transfer(dep);
+	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
+		dep->frame_number = DWC3_ALIGN_FRAME(dep, i);
+
+		ret = __dwc3_gadget_kick_transfer(dep);
+		if (ret != -EAGAIN)
+			break;
+	}
+
+	return ret;
 }
 
 static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
-- 
2.19.1