Hi,
Thinh Nguyen <thinh.nguyen@xxxxxxxxxxxx> writes:
>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>> index d8c7ad0c22e8..00fe01a01977 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -1268,12 +1268,22 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
>>>>
>>>> static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
>>>> {
>>>> + u64 current_timestamp;
>>>> + u64 diff_timestamp;
>>>> + u32 elapsed_frames;
>>>> +
>>>> 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);
>>>> +
>>>> + dep->frame_number += elapsed_frames;
>>>> dep->frame_number = DWC3_ALIGN_FRAME(dep);
>>>> +
>>>> return __dwc3_gadget_kick_transfer(dep);
>>>> }
>>>>
>>>> @@ -2320,6 +2330,7 @@ static void dwc3_gadget_endpoint_frame_from_event(struct dwc3_ep *dep,
>>>> const struct dwc3_event_depevt *event)
>>>> {
>>>> dep->frame_number = event->parameters;
>>>> + dep->frame_timestamp = ktime_get_ns();
>>>> }
>>>>
>>>> static void dwc3_gadget_endpoint_transfer_in_progress(struct dwc3_ep *dep,
>>> This may not be enough. The dep->frame_timestamp may not correspond to
>>> the frame_number from XferNotReady event. When there's system latency
>>> (which is possible when this failure happens), the time the driver
>>> handle the event may be a few uframes passed the time the controller's
>>> XferInProgress uframe parameter.
>>>
>>> Rather than starting the isoc transfer immediately on the next interval.
>>> How about starting the transfer with some minimum buffer uframes just
>>> like before? (e.g. frame_number + max(4, interval))
>> The problem with this is cases with interval of 1ms. This will result in
>> a 4ms delay. I really want to start transfer as soon as possible and the
>> timestamp trick seems to be the best idea so far, without resorting to
>> 4 intervals delay. We do, however, have the possibility that this will
>> start 2 intervals in the future because of the usage of
>> DIV_ROUND_UP_ULL() and because of how DWC3_ALIGN_FRAME() is implemented.
>>
>> I understand what you're saying, though, but it seems like we don't
>> have to avoid that case completely. We can only make it less likely.
>>
>
> 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);
+ dep->frame_number = DWC3_ALIGN_FRAME(dep);
- 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)
--
balbi
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