Hi Vinod, When I thought that all corner cases are handled I got report of a failure on a miss-configured setup: UART without lines connected Enable HW flow control (nothing is connected) Do a small tx like "dd if=/dev/urandom of=/dev/ttyS1 bs=128 count=1" The result is an interrupt flood caused by constant TDCM reception. The explanation comes from the DMA split design and explained in patch 3: "If the peripheral is disabled (or it is not able to send out data) the UDMAP will complete a 'short' transfer. In other words: if the amount of data can fit into PSI-L and PDMA (and peripheral FIFO) then UDMAP will send out the data and return as the transfer is completed, however the peripheral did not actually received all the data. It was wrong to issue a normal teardown on the channel for several reasons: UDMAP is not processing any packet so it will just return the TDCM and if the peripheral is not consuming data from PDMA then we will have constant flood of TDCMs (interrupts). After the teardown the channel will be in reset state and we would need to reset the rings as well, but it can not be done in interrupt context. If the peripheral is just slow to consume data or even there is a delay between starting the DMA then we will have again issues detecting the state. We could set force teardown, but that will make PDMA to discard the data which is not correct in case of slow or delayed transfer start on the peripheral. The only solution is to use a work and check the progress in there after the descriptor is returned and the UDMA and PDMA counters are not showing the same number of bytes processed." I'll squash these to v7, but I thought that this change is better to be visible alone as it is kind of a big one on handling the early TX completion. Regards, Peter --- Peter Ujfalusi (3): dmaengine: ti: k3-udma: Correct completed descriptor's residue value dmaengine: ti: k3-udma: Workaround for stale transfers dmaengine: ti: k3-udma: Fix early TX completion against PDMAs drivers/dma/ti/k3-udma.c | 89 +++++++++++++++++++++++++++++----------- 1 file changed, 66 insertions(+), 23 deletions(-) -- Peter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
