On 7/18/2017 11:53 AM, Felipe Balbi wrote:
> Hi,
>
> Manu Gautam <mgautam@xxxxxxxxxxxxxx> writes:
>> The PIDs for Isochronous data transfers are incorrect
>> for high bandwidth IN endpoints when the request length
>> is less than EP wMaxPacketSize.
>> As per spec correct PIDs for ISOC data transfers are:
>> ->For request length < maxPayloadSize
>> - DATA0,
>> ->For maxPayloadSize < length < 2*maxPayloadSize
>> - DATA0,DATA1
>> ->For 2*maxPayloadSize < length < 3*maxPayloadSize
>> - DATA2, DATA1, DATA0.
>>
>> Fix this by setting the PCM field of trb->size depending
>> on request length rather than fixing it to the value
>> depending on wMaxPacketSize.
>>
>> Ideally it shouldn't give any issues as dwc3 will send
>> 0-length packet for next IN token if host sends even
>> after receiving a short packet. Windows seems to ignore
>> this but with MacOS frame loss observed when using f_uvc.
>>
>> Signed-off-by: Manu Gautam <mgautam@xxxxxxxxxxxxxx>
> Roger, you guys have been using isoc transfers lately. Does this work
> for you? Is the current setup really buggy in any way?
>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index aea9a5b..b81547d 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -854,8 +854,13 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
>> trb->ctrl = DWC3_TRBCTL_ISOCHRONOUS_FIRST;
>>
>> if (speed == USB_SPEED_HIGH) {
>> - struct usb_ep *ep = &dep->endpoint;
>> - trb->size |= DWC3_TRB_SIZE_PCM1(ep->mult - 1);
>> + unsigned int maxp = usb_endpoint_maxp(
>> + dep->endpoint.desc);
>> + unsigned int rem = length % maxp;
>> + unsigned int mult = (length / maxp) & 0x3;
>> +
>> + trb->size |= DWC3_TRB_SIZE_PCM1(
>> + rem ? mult : mult - 1);
> Manu, It seems to me like we shouldn't be relying on req->length. Which
> gadget driver are you using to test this?
f_uvc function is used.
In bus analyzer logs there are DATA2, DATA1 PIDs even for a 2K byte TRB
(also last packet of the video frame are always less than maxpacket size).
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