Dear Doug,
? 2018?05?02? 13:02, Doug Anderson ??:
> Hi,
>
> On Tue, May 1, 2018 at 8:04 PM, William Wu <william.wu at rock-chips.com> wrote:
>> If isoc split in transfer with no data (the length of DATA0
>> packet is zero), we can't simply return immediately. Because
>> the DATA0 can be the first transaction or the second transaction
>> for the isoc split in transaction. If the DATA0 packet with no
>> data is in the first transaction, we can return immediately.
>> But if the DATA0 packet with no data is in the second transaction
>> of isoc split in transaction sequence, we need to increase the
>> qtd->isoc_frame_index and giveback urb to device driver if needed,
>> otherwise, the MDATA packet will be lost.
>>
>> A typical test case is that connect the dwc2 controller with an
>> usb hs Hub (GL852G-12), and plug an usb fs audio device (Plantronics
>> headset) into the downstream port of Hub. Then use the usb mic
>> to record, we can find noise when playback.
>>
>> In the case, the isoc split in transaction sequence like this:
>>
>> - SSPLIT IN transaction
>> - CSPLIT IN transaction
>> - MDATA packet (176 bytes)
>> - CSPLIT IN transaction
>> - DATA0 packet (0 byte)
>>
>> This patch use both the length of DATA0 and qtd->isoc_split_offset
>> to check if the DATA0 is in the second transaction.
>>
>> Signed-off-by: William Wu <william.wu at rock-chips.com>
>> ---
>> Changes in v2:
>> - Modify the commit message
>>
>> drivers/usb/dwc2/hcd_intr.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
>> index 5e2378f..479f628 100644
>> --- a/drivers/usb/dwc2/hcd_intr.c
>> +++ b/drivers/usb/dwc2/hcd_intr.c
>> @@ -930,7 +930,7 @@ static int dwc2_xfercomp_isoc_split_in(struct dwc2_hsotg *hsotg,
>> frame_desc = &qtd->urb->iso_descs[qtd->isoc_frame_index];
>> len = dwc2_get_actual_xfer_length(hsotg, chan, chnum, qtd,
>> DWC2_HC_XFER_COMPLETE, NULL);
>> - if (!len) {
>> + if (!len && !qtd->isoc_split_offset) {
>> qtd->complete_split = 0;
>> qtd->isoc_split_offset = 0;
>> return 0;
> I don't think my USB-fu is strong enough to do a real review of this
> patch, but one small nitpick is that you can remove
> "qtd->isoc_split_offset = 0" in the if test now. AKA:
>
> if (!len && !qtd->isoc_split_offset) {
> qtd->complete_split = 0;
> return 0;
> }
Yes, good idea! I will fix it in next patch. Thank you!
>
> ...since you only enter the "if" test now when isoc_split_offset is
> already 0... Hopefully John Youn will have some time to comment on
> this patch with more real USB knowledge...
>
>
> -Doug
>
Best regards,
???? wulf
>
