On Thu, Jan 19, 2017 at 07:04:57AM -0800, Tony Lindgren wrote: > * Bin Liu <b-liu@xxxxxx> [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. Regards, -Bin. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
