I have the following over on the Xilinx forum - so far no one's looked at it. (so few people doing DMA? ;) )
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I'm using dma_alloc_coherent for dma operations -- and it works great as long as the transaction doesn't timeout. (which is a condition that's expected to occur).
After the initial timeout, DMA stops working for every subsequent attempt. (see below)
dma_terminate_all() looks like should be what I should use, but I get first time use dmesg of:
[ 35.146414] xilinx-dma 40400000.dma: Cannot stop channel eeaff410: 0 [ 36.151393] xilinx-dma 40400000.dma: Cannot stop channel eea30350: 0
(DMA doesn't clean up -- and doesn't go back to working -- and no more messages like the above occur on sequential timeouts.)
Is there some cleanup step I'm missing? (this is Petalinux 2015.4)
Thanks,
-Ben
I originally used kzalloc with small buffers combined with the sequence of: (get/release dma channel is on open/close of driver)
dma_map_single () dmaengine_prep_slave_single () init_completion() dma_async_issue() wait_for_completion_timeout() ucpi_dma_ch_unmap()
it worked fine.
I switched to dma_mmap_coherent() and the sequence is now: (get/release dma channel is on open/close of driver)
dmaengine_prep_slave_single () init_completion() dma_async_issue() wait_for_completion_timeout() (tried with dma_terminate_call() and without) ucpi_dma_ch_unmap()
