Greg, On Wed, Jan 30, 2019 at 09:24:04AM +0100, Greg Kroah-Hartman wrote: > On Mon, Jan 28, 2019 at 02:01:51PM -0600, Bin Liu wrote: > > From: Paul Elder <paul.elder@xxxxxxxxxxxxxxxx> > > > > 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> > > Signed-off-by: Bin Liu <b-liu@xxxxxx> > > No "Fixes:" tag? This patch changes the logic which was there in the very first commit of the musb drivers more than a decade ago, so it seems the issue was there from day one. I didn't add the 'Fixes:' tag, was thinking it doesn't add any value. Do you want me to add it? Fixes: 550a7375fe72 ("USB: Add MUSB and TUSB support") > > No need for stable? The patch might not be applied on stable cleanly. I was thinking to send out backport patches for applicable stable trees once this patch got in v5.0 -rc. > > That seems odd... Indeed, this is a forward-port from 2.6.34. Regards, -Bin.
