On Wed, Sep 21, 2016 at 11:01:21AM +0300, Felipe Balbi wrote:
>
> Hi,
>
> Bin Liu <b-liu@xxxxxx> writes:
> > Hi,
> >
> > I am trying to check Isoch high bandwidth transfer with g_webcam.ko in
> > high-speed connection.
> >
> > First I hacked webcam.c as follows to enable 640x480@30fps mode.
> >
> > diff --git a/drivers/usb/gadget/legacy/webcam.c b/drivers/usb/gadget/legacy/webcam.c
> > index 72c976b..9eb315f 100644
> > --- a/drivers/usb/gadget/legacy/webcam.c
> > +++ b/drivers/usb/gadget/legacy/webcam.c
> > @@ -191,15 +191,15 @@ static const struct UVC_FRAME_UNCOMPRESSED(3) uvc_frame_yuv_360p = {
> > .bFrameIndex = 1,
> > .bmCapabilities = 0,
> > .wWidth = cpu_to_le16(640),
> > - .wHeight = cpu_to_le16(360),
> > + .wHeight = cpu_to_le16(480),
> > .dwMinBitRate = cpu_to_le32(18432000),
> > .dwMaxBitRate = cpu_to_le32(55296000),
> > - .dwMaxVideoFrameBufferSize = cpu_to_le32(460800),
> > - .dwDefaultFrameInterval = cpu_to_le32(666666),
> > + .dwMaxVideoFrameBufferSize = cpu_to_le32(614400),
> > + .dwDefaultFrameInterval = cpu_to_le32(333333),
> > .bFrameIntervalType = 3,
> > - .dwFrameInterval[0] = cpu_to_le32(666666),
> > - .dwFrameInterval[1] = cpu_to_le32(1000000),
> > - .dwFrameInterval[2] = cpu_to_le32(5000000),
> > + .dwFrameInterval[0] = cpu_to_le32(333333),
> > + .dwFrameInterval[1] = cpu_to_le32(666666),
> > + .dwFrameInterval[2] = cpu_to_le32(1000000),
> > };
> >
> > then loaded g_webcam.ko as
> >
> > # modprobe g_webcam streaming_maxpacket=3072
> >
> > The endpoint descriptor showing on the host is
> >
> > Endpoint Descriptor:
> > bLength 7
> > bDescriptorType 5
> > bEndpointAddress 0x8d EP 13 IN
> > bmAttributes 5
> > Transfer Type Isochronous
> > Synch Type Asynchronous
> > Usage Type Data
> > wMaxPacketSize 0x1400 3x 1024 bytes
> > bInterval 1
> >
> > However the usb bus trace shows only one transaction with 1024-bytes packet in
> > every SOF. The host only sends one IN packet in every SOF, I am expecting 2~3
> > 1024-bytes transactions, since this would be required to transfer 640x480@30fps
> > YUV frames in high-speed.
> >
> > DId I miss anything in the setup?
>
> MUSB or DWC3? This looks like a UDC bug to me. Can you show a screenshot
Happened on both MUSB and DWC3.
> of your bus analyzer? When host sends IN token, are you replying with
The trace screenshot on DWC3 is attached.
> DATA0, DATA1 or DATA2?
Good hint! It is DATA0!
>
> --
> balbi
Regards,
-Bin.
Attachment:
dwc3-g_webcam-DATA0-only-bus-trace.png
Description: PNG image
