usb: dwc3: gadget: check if dep->frame_number is still valid

Quoted 44 lines

Quoted 4 lines

If it fails for over 5 times in a row, then we should probably wait for the next XferNotReady to get the frame_number again. Also 5 is an arbitrary number I came up without any testing, we can probably decide on a better number. What do you think?

I have this now:

drivers/usb/dwc3/core.h +1 -0

index 131028501752..3390fa46ea30 100644
@@ -37,6 +37,7 @@
 #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

drivers/usb/dwc3/gadget.c +5 -1

index d8c7ad0c22e8..1590516735cb 100644
@@ -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;
        }
 

drivers/usb/dwc3/gadget.c static int __dwc3_gadget_get_frame(struct dwc3 *dwc) · line 1281

Quoted 4 lines

drivers/usb/dwc3/gadget.c +2 -2

-       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);

Shouldn't this be like this?
dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);

Quoted 11 lines

drivers/usb/dwc3/gadget.c +7 -0

+
+               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)

Quoted 3 lines

This means we will increment in full intervals, up to 5 intervals in the future. If it still fails, then there's not much we can do.

I agree. Also, depending on the application requirement, we may want to giveback/cleanup request(s) every time we fail so that the data won't be pushed back/delayed for too long.
We could experiment and decide on the maximum delay time (base on the service interval length and number of retries) to be considered acceptable to start giveback stale requests.