[v2] usb: gadget: musb: fix short isoc packets with inventra dma

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Jan 30, 2019 at 08:13:21AM -0600, Bin Liu wrote:
> From: Paul Elder <paul.elder@ideasonboard.com>
> 
> 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
> 
> Fixes: 550a7375fe72 ("USB: Add MUSB and TUSB support")
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> Signed-off-by: Bin Liu <b-liu@ti.com>
> Cc: stable <stable@vger.kernel.org>
> ---
> v2: add Fixes tag.

I added a stable tag so that you get notified by my scripts if/when it
fails to apply.  Otherwise Sasha's scripts are going to try to evaluate
it and determine if this needs to be backported or not, and we already
know that it does need to be, so let's not waste their time.

thanks,

greg k-h