[PATCH 14/14] usb: dwc3: gadget: check if dep->frame_number is still valid

[Felipe Balbi]

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.ba...@linux.intel.com>
---
 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