Hi,
Manu Gautam <mgau...@codeaurora.org> writes:
>> Manu Gautam <mgau...@codeaurora.org> 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 <mgau...@codeaurora.org>
>> 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).
Understood, yeah it makes sense, although I think your patch can be
simplified. Seems to me that it should be enough to set PCM1 to
req->length / usb_endpoint_maxp(), no?
Or, if we want to make use of ep->mult, we could:
unsigned int mult = ep->mult - 1;
if (req->length < (usb_endpoint_maxp() << 1))
mult--;
if (req->length < usb_endpoint_maxp())
mult--;
trb->size |= DWC3_TRB_SIZE_PCM1(mult);
how about that?
--
balbi
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