Hi Bin, On Wed, Jan 09, 2019 at 09:02:15AM -0600, Bin Liu wrote: > Hi Paul, > > On Wed, Jan 09, 2019 at 02:10:09AM -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 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 | 19 +++++-------------- > > drivers/usb/musb/musbhsdma.c | 21 +++++++++++---------- > > 2 files changed, 16 insertions(+), 24 deletions(-) > > > > diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c > > index eae8b1b1b45b..496643f54faa 100644 > > --- a/drivers/usb/musb/musb_gadget.c > > +++ b/drivers/usb/musb/musb_gadget.c > > @@ -452,13 +452,10 @@ void musb_g_tx(struct musb *musb, u8 epnum) > > } > > > > if (request) { > > - u8 is_dma = 0; > > - bool short_packet = false; > > > > trace_musb_req_tx(req); > > > > if (dma && (csr & MUSB_TXCSR_DMAENAB)) { > > - is_dma = 1; > > csr |= MUSB_TXCSR_P_WZC_BITS; > > csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN | > > MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET); > > @@ -476,16 +473,8 @@ void musb_g_tx(struct musb *musb, u8 epnum) > > */ > > if ((request->zero && request->length) > > && (request->length % musb_ep->packet_sz == 0) > > - && (request->actual == request->length)) > > - short_packet = true; > > + && (request->actual == request->length)) { > > > > - if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) && > > - (is_dma && (!dma->desired_mode || > > - (request->actual & > > - (musb_ep->packet_sz - 1))))) > > - short_packet = true; > > - > > - if (short_packet) { > > /* > > * On DMA completion, FIFO may not be > > * available yet... > > @@ -493,8 +482,10 @@ void musb_g_tx(struct musb *musb, u8 epnum) > > if (csr & MUSB_TXCSR_TXPKTRDY) > > return; > > > > - musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE > > - | MUSB_TXCSR_TXPKTRDY); > > + musb_dbg(musb, "sending short pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n", > > + request->zero, request->length, request->actual, > > + dma->desired_mode); > > + musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY); > > Sorry I didn't catch this in the last review, but this change seems not > required, isn't it? In the first version of the patch, the code is > 'returned' in the 'if (musb_dma_inventra())' branch above, doesn't reach > here. Do you mean change compared to the last version of the patch, or this last chunk of the diff? I guess I did also remove the return when I removed the 'if (musb_dma_inventra())' block that had the FLUSHFIFIO, but when I tested it it still worked. In fact, I reverted this last diff chunk and it still worked. Paul
