[PATCH 2/4] 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.

Before kicking the transfer, let's check if current frame number is
still less than our aligned frame number that we got from the
previous XferNotReady. If it isn't, then we'll increment
dep->frame_number to make sure it's ahead of current frame number.

Signed-off-by: Felipe Balbi <felipe.ba...@linux.intel.com>
---
 drivers/usb/dwc3/core.h   |  2 ++
 drivers/usb/dwc3/gadget.c | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 285ce0ef3b91..3acf8788a680 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -685,6 +685,8 @@ struct dwc3_ep {
        u8                      type;
        u8                      resource_index;
        u32                     frame_number;
+#define DWC3_EP_FRAME_NUMBER_MASK 0x3fff
+
        u32                     interval;
 
        char                    name[20];
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index f61a4250c883..0bac9b02f28b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1257,6 +1257,9 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
 
 static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 {
+       u16 current_frame_number;
+       u16 frame_number;
+
        if (list_empty(&dep->pending_list)) {
                dev_info(dep->dwc->dev, "%s: ran out of requests\n",
                                dep->name);
@@ -1265,6 +1268,14 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
        }
 
        dep->frame_number = DWC3_ALIGN_FRAME(dep);
+       current_frame_number = __dwc3_gadget_get_frame(dep->dwc);
+       frame_number = dep->frame_number & DWC3_EP_FRAME_NUMBER_MASK;
+
+       if (frame_number <= current_frame_number) {
+               dep->frame_number += current_frame_number - frame_number;
+               dep->frame_number = DWC3_ALIGN_FRAME(dep);
+       }
+
        return __dwc3_gadget_kick_transfer(dep);
 }
 
-- 
2.18.0