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. Regards, -Bin.
