Re: [PATCH 2/2] usb: musb: Size 1 dma in transfers won't complete with cpp41

[Bin Liu <b-liu-l0cyMroinI0@public.gmane.org>]

On Thu, Jan 19, 2017 at 08:15:45AM -0800, Tony Lindgren wrote:
> * Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> [170119 07:57]:
> > * Bin Liu <b-liu-l0cyMroinI0@public.gmane.org> [170119 07:14]:
> > > On Thu, Jan 19, 2017 at 07:04:57AM -0800, Tony Lindgren wrote:
> > > > * Bin Liu <b-liu-l0cyMroinI0@public.gmane.org> [170118 19:42]:
> > > > > On Wed, Jan 18, 2017 at 06:29:59PM -0800, Tony Lindgren wrote:
> > > > > > At least with the cppi41 dma, size 1 in dma transfers will just wait
> > > > > 
> > > > > In which case do you see the size 1 transfer? using testusb?
> > > > > 
> > > > > > until the device is disconnected. This causes timeouts in cppi41 dma
> > > > > > runtime PM.
> > > > > > 
> > > > > > Also the initial size 8 transfers take about 200ms to complete when
> > > > > > plugging a USB mass storage device to a hub. But we probably want to
> > > > > > keep those to avoid using PIO.
> > > > > > 
> > > > > > Fix the issue by adding a quirk for cppi41 and skip size 1 in dma if
> > > > > > set.
> > > > > 
> > > > > It is fine to bypass dma for size 1 transfers, due to the dma setup
> > > > > overhead. But I'd like to know the test case to understand why it hangs.
> > > > 
> > > > The test case is the same old connect a USB mass storage device to a hub.
> > > > There we see the initial size 1 transfer in the beginning. That transfer
> > > > seems to never complete with cppi41 and the transfer will stay active
> > > > until the device is disconnected. Currently we don't seem to have any
> > > > timeout mechanism in cppi41 for that.
> > > 
> > > Ok, I will take a look maybe sometime next week to understand the
> > > traffic.
> > > 
> > > BTY, it seems you missed my comment at the end which is about limiting
> > > the transfer size.
> > 
> > Oops sorry yeah you're right, -ENOTENOUGHCOFFEEYET.
> 
> Oh and testing that fix made me notice that this patch 2/2 problem is now
> gone with my current cppi41 dma fixes. So let's drop this patch 2/2, it
> seems to be just a workaround for a runtime PM autosuspend delay getting
> timed out for the dma transfer.
> 
> Patch 1/2 of this series should be still applied for the -rc cycle.

Sounds good. I wil do more check on 1/2 then send it to Greg.

Regards,
-Bin.
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