On Mon, Sep 23, 2019 at 8:58 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 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 manually retrigger the sdma script for > this channel and by this dissolve the freeze. > > While this seems to work fine so far, it may come to buffer overruns > when the channel - even temporary - is stopped. This case has to be > addressed by device drivers by increasing the number of DMA periods. > > 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. > Using the 4.19.y branch, this seems to working just fine for me with an i.MX6Q with WL1837MOD Bluetooth connected to UART2. I am still seeing some timeouts with 5.3, but I'm going to continue to run some tests. Tested-by: Adam Ford <aford173@xxxxxxxxx> #imx6q w/ 4.19 Kernel > Signed-off-by: Philipp Puschmann <philipp.puschmann@xxxxxxxxx> > Reviewed-by: Fugang Duan <fugang.duan@xxxxxxx> > > --- > > Changelog v5: > - join with patch version from Jan Luebbe > - adapt comments and patch descriptions > - add Reviewed-by > > Changelog v4: > - fixed the fixes tags > > Changelog v3: > - fixes typo in dma_wmb > - add fixes tags > > Changelog v2: > - adapt title (this patches are not only for i.MX6) > - improve some comments and patch descriptions > - add a dma_wb() around BD_DONE flag > - add Reviewed-by tags > - split off "serial: imx: adapt rx buffer and dma periods" > > Philipp Puschmann (3): > dmaengine: imx-sdma: fix buffer ownership > dmaengine: imx-sdma: fix dma freezes > dmaengine: imx-sdma: drop redundant variable > > drivers/dma/imx-sdma.c | 37 +++++++++++++++++++++++++++---------- > 1 file changed, 27 insertions(+), 10 deletions(-) > > -- > 2.23.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
