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

[Felipe Balbi <felipe.balbi@linux.intel.com>]

Hi again,

Felipe Balbi <felipe.balbi@linux.intel.com> writes:
> In the case of interval of 1ms, it will start on the next interval.
>> frame_number + max(4, interval) will start at least 4 uframes in the future.
>>
>> In any case, what about immediately retry the START_TRANSFER command
>> with a new frame_number + (interval*retry) should it fail with
>> bus-expiry? You can set the number of retries to maybe 5 times. This
>> should remove the need to do time stamping.
>
> That seems like a good idea. Something like below? (on top of $subject)
>
> modified   drivers/usb/dwc3/core.h
> @@ -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
> modified   drivers/usb/dwc3/gadget.c
> @@ -1271,20 +1271,29 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>  	u64 current_timestamp;
>  	u64 diff_timestamp;
>  	u32 elapsed_frames;
> +	int retries;
> +	int delta = 1
> +	int ret;
>  
>  	if (list_empty(&dep->pending_list)) {
>  		dep->flags |= DWC3_EP_PENDING_REQUEST;
>  		return -EAGAIN;
>  	}
>  
> -	current_timestamp = ktime_get_ns();
> -	diff_timestamp = current_timestamp - dep->frame_timestamp;
> -	elapsed_frames = DIV_ROUND_UP_ULL(diff_timestamp, 125000);
> +	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
> +		current_timestamp = ktime_get_ns();
> +		diff_timestamp = current_timestamp - dep->frame_timestamp;
> +		elapsed_frames = DIV_ROUND_UP_ULL(diff_timestamp, 125000);
>  
> -	dep->frame_number += elapsed_frames;
> -	dep->frame_number = DWC3_ALIGN_FRAME(dep);
> +		dep->frame_number += elapsed_frames + (delta * i);

the other possibility is that we can call DWC3_ALIGN_FRAME() n times
since that will put the transfer on the following interval. That would
look like so:

modified   drivers/usb/dwc3/core.h
@@ -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
modified   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))
 
 /**
@@ -1271,20 +1271,28 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 	u64 current_timestamp;
 	u64 diff_timestamp;
 	u32 elapsed_frames;
+	int retries;
+	int ret;
 
 	if (list_empty(&dep->pending_list)) {
 		dep->flags |= DWC3_EP_PENDING_REQUEST;
 		return -EAGAIN;
 	}
 
-	current_timestamp = ktime_get_ns();
-	diff_timestamp = current_timestamp - dep->frame_timestamp;
-	elapsed_frames = DIV_ROUND_UP_ULL(diff_timestamp, 125000);
+	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
+		current_timestamp = ktime_get_ns();
+		diff_timestamp = current_timestamp - dep->frame_timestamp;
+		elapsed_frames = DIV_ROUND_UP_ULL(diff_timestamp, 125000);
 
-	dep->frame_number += elapsed_frames;
-	dep->frame_number = DWC3_ALIGN_FRAME(dep);
+		dep->frame_number += elapsed_frames;
+		dep->frame_number = DWC3_ALIGN_FRAME(dep, i);
 
-	return __dwc3_gadget_kick_transfer(dep);
+		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)