[Adding Robin and Andy] On Wed, Sep 11, 2019 at 11:50 AM Philipp Puschmann <philipp.puschmann@xxxxxxxxx> wrote: > > For some years and since many kernel versions there are reports that > RX UART DMA channel stops working at one point. So far the usual workaround was > to disable RX DMA. This patches try to fix the underlying problem. > > When a running sdma script does not find any usable destination buffer to put > its data into it just leads to stopping the channel being scheduled again. As > solution we we manually retrigger the sdma script for this channel and by this > dissolve the freeze. > > While this seems to work fine so far a further patch in this series increases > the number of RX DMA periods for UART to reduce use cases running into such > a situation. > > This patch series was tested with the current kernel and backported to > kernel 4.15 with a special use case using a WL1837MOD via UART and provoking > the hanging of UART RX DMA within seconds after starting a test application. > It resulted in well known > "Bluetooth: hci0: command 0x0408 tx timeout" > errors and complete stop of UART data reception. Our Bluetooth traffic consists > of many independent small packets, mostly only a few bytes, causing high usage > of periods. > > > Philipp Puschmann (4): > dmaengine: imx-sdma: fix buffer ownership > dmaengine: imx-sdma: fix dma freezes > serial: imx: adapt rx buffer and dma periods > dmaengine: imx-sdma: drop redundant variable > > drivers/dma/imx-sdma.c | 32 ++++++++++++++++++++++---------- > drivers/tty/serial/imx.c | 5 ++--- > 2 files changed, 24 insertions(+), 13 deletions(-) > > -- > 2.23.0 >
