Hi Bin, Felipe, We have been trying to get a UVC gadget operational on the Pandaboard ES platform, and we believe we've hit an issue with short packets on the MUSB in DMA mode.
Using the g_webcam module, I can instantiate a UVC video node, and use the uvc-gadget helper application [0] to handle the frame generation. With DMA disabled using CONFIG_MUSB_PIO_ONLY I am able to process frames on the host using yavta [1] However when DMA is enabled, only the first frame is transmitted to the host, and I get an error from the musb_log debug prints which indicate that the MUSB_TXCSR_TXPKTRDY is not cleared following a short packet. A capture of the musb_log trace-points [2] shows the following at the end of the log: The 'mode' has been set to '0' instead of '1', buffer length is 902 instead of 1024 (expected behaviour for the last packet): "ep13-Tx pkt_sz 1024, dma_addr 0xadfbbc00 length 902, mode 0" And then there is a fault reported: "ep13 old packet still ready , txcsr 2003" The host (linux, running the uvc driver with extra debug prints) reports: [24517.711147] uvcvideo: decode_data: len: 1022, maxlen 460800 [24517.759117] uvcvideo: decode_data: len: 1022, maxlen 459778 <snip> ... [24529.375018] uvcvideo: decode_data: len: 1022, maxlen 2944 [24529.399073] uvcvideo: decode_data: len: 1022, maxlen 1922 [24529.427014] uvcvideo: decode_data: len: 900, maxlen 900 And receives no further data following the end of the first frame. Are there any known issues on the musb-gadget with short-packet handling - or any other tests I can perform to check this ? Should I be looking to try to get the txstate() call to re-execute after a delay (using musb_queue_resume_work() perhaps?) or does this indicate that the hardware has jammed ? Stopping the pipeline (the yavta capture) and restarting, will successfully transfer (only) the first frame again. Any other hints and tips appreciated! [0] git://git.ideasonboard.org/uvc-gadget.git [1] git://git.ideasonboard.org/yavta.git [2] http://paste.ubuntu.com/p/QHrh5XzZv8/ -- Regards Kieran
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