On Tue, Jan 15, 2019 at 07:01:45PM -0500, Paul Elder wrote: > Handling short packets (length < max packet size) in the Inventra DMA > engine in the MUSB driver causes the MUSB DMA controller to hang. An > example of a problem that is caused by this problem is when streaming > video out of a UVC gadget, only the first video frame is transferred. > > For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be > set manually by the driver. This was previously done in musb_g_tx > (musb_gadget.c), but incorrectly (all csr flags were cleared, and only > MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem > allows some requests to be transferred correctly, but multiple requests > were often put together in one USB packet, and caused problems if the > packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY > in dma_controller_irq (musbhsdma.c), just like host mode transfers. > > This topic was originally tackled by Nicolas Boichat [0] [1] and is > discussed further at [2] as part of his GSoC project [3]. > > [0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU > [1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9 > [2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html > [3] http://elinux.org/BeagleBoard/GSoC/USBSniffer > > Signed-off-by: Paul Elder <paul.elder@xxxxxxxxxxxxxxxx> > --- > Changes in v3: > > - remove unnecessary chunk for sending short packet > > Changes in v2: > > - no more flushing FIFO > - greatly simplified short packet if guard in musb_g_tx, and removed > unnecessary variables > - minor indentation and wording changes > drivers/usb/musb/musb_gadget.c | 13 +------------ > drivers/usb/musb/musbhsdma.c | 21 +++++++++++---------- > 2 files changed, 12 insertions(+), 22 deletions(-) Applied. Thanks. Regards, -Bin.
