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

[Bin Liu <b-liu@ti.com>]

On Wed, Jan 30, 2019 at 03:49:26PM +0100, Greg Kroah-Hartman wrote:
> 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.

Sounds good. Thanks.

I track those musb patches which require manual backport - it doesn't
happen very often. But since You and Sasha already have an automation to
take care of the tasks, I from now on will add 'cc: stable' whenever
applicable and let the scripts to alert me when any action is needed.

Regards,
-Bin.