From: Philipp Puschmann <philipp.puschm...@emlix.com> Sent: Thursday, September 19, 2019 10:30 PM > 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. > > 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 | 32 ++++++++++++++++++++++---------- > 1 file changed, 22 insertions(+), 10 deletions(-) > > -- > 2.23.0
The patch set look fine that is really to fix some corner issue from the logical view. Reviewed-by: Fugang Duan <fugang.d...@nxp.com>
