Re: g_webcam Isoch high bandwidth transfer

[Bin Liu <b-liu@ti.com>]

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On Wed, Sep 21, 2016 at 11:01:21AM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> Bin Liu <b-liu@ti.com> 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.

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