Re: g_webcam Isoch high bandwidth transfer

[Felipe Balbi <felipe.balbi@linux.intel.com>]

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Hi,

Bin Liu <b-liu@ti.com> writes:
> 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!

yeah, should've been DATA2. I'll check if we're missing anything for
High Bandwidth Iso on DWC3. Can you confirm if it works of tails on
DWC3? On your follow-up mail you mentioned it's a bug in MUSB. What
about DWC3?

-- 
balbi

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